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llvm-project/llvm/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp

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[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
//===------ PPCLoopPreIncPrep.cpp - Loop Pre-Inc. AM Prep. Pass -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a pass to prepare loops for pre-increment addressing
// modes. Additional PHIs are created for loop induction variables used by
// load/store instructions so that the pre-increment forms can be used.
// Generically, this means transforming loops like this:
// for (int i = 0; i < n; ++i)
// array[i] = c;
// to look like this:
// T *p = array[-1];
// for (int i = 0; i < n; ++i)
// *++p = c;
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "ppc-loop-preinc-prep"
#include "PPC.h"
#include "PPCTargetMachine.h"
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
#include "llvm/ADT/DepthFirstIterator.h"
Re-sort #include lines using my handy dandy ./utils/sort_includes.py script. This is in preparation for changes to lots of include lines. llvm-svn: 229088
2015-02-13 17:09:03 +08:00
#include "llvm/ADT/STLExtras.h"
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IntrinsicInst.h"
Make DataLayout Non-Optional in the Module Summary: DataLayout keeps the string used for its creation. As a side effect it is no longer needed in the Module. This is "almost" NFC, the string is no longer canonicalized, you can't rely on two "equals" DataLayout having the same string returned by getStringRepresentation(). Get rid of DataLayoutPass: the DataLayout is in the Module The DataLayout is "per-module", let's enforce this by not duplicating it more than necessary. One more step toward non-optionality of the DataLayout in the module. Make DataLayout Non-Optional in the Module Module->getDataLayout() will never returns nullptr anymore. Reviewers: echristo Subscribers: resistor, llvm-commits, jholewinski Differential Revision: http://reviews.llvm.org/D7992 From: Mehdi Amini <mehdi.amini@apple.com> llvm-svn: 231270
2015-03-05 02:43:29 +08:00
#include "llvm/IR/Module.h"
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
Re-sort #include lines using my handy dandy ./utils/sort_includes.py script. This is in preparation for changes to lots of include lines. llvm-svn: 229088
2015-02-13 17:09:03 +08:00
#include "llvm/Transforms/Scalar.h"
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
[PowerPC] Handle loop predecessor invokes If a loop predecessor has an invoke as its terminator, and the return value from that invoke is used to determine the loop iteration space, then we can't insert a computation based on that value in the loop predecessor prior to the terminator (oops). If there's such an invoke, or just no predecessor for that matter, insert a new loop preheader. llvm-svn: 228488
2015-02-07 15:32:58 +08:00
#include "llvm/Transforms/Utils/LoopUtils.h"
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
#include "llvm/Transforms/Utils/ValueMapper.h"
using namespace llvm;
// By default, we limit this to creating 16 PHIs (which is a little over half
// of the allocatable register set).
static cl::opt<unsigned> MaxVars("ppc-preinc-prep-max-vars",
cl::Hidden, cl::init(16),
cl::desc("Potential PHI threshold for PPC preinc loop prep"));
namespace llvm {
void initializePPCLoopPreIncPrepPass(PassRegistry&);
}
namespace {
class PPCLoopPreIncPrep : public FunctionPass {
public:
static char ID; // Pass ID, replacement for typeid
PPCLoopPreIncPrep() : FunctionPass(ID), TM(nullptr) {
initializePPCLoopPreIncPrepPass(*PassRegistry::getPassRegistry());
}
PPCLoopPreIncPrep(PPCTargetMachine &TM) : FunctionPass(ID), TM(&TM) {
initializePPCLoopPreIncPrepPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addPreserved<LoopInfoWrapperPass>();
[PM] Port ScalarEvolution to the new pass manager. This change makes ScalarEvolution a stand-alone object and just produces one from a pass as needed. Making this work well requires making the object movable, using references instead of overwritten pointers in a number of places, and other refactorings. I've also wired it up to the new pass manager and added a RUN line to a test to exercise it under the new pass manager. This includes basic printing support much like with other analyses. But there is a big and somewhat scary change here. Prior to this patch ScalarEvolution was never *actually* invalidated!!! Re-running the pass just re-wired up the various other analyses and didn't remove any of the existing entries in the SCEV caches or clear out anything at all. This might seem OK as everything in SCEV that can uses ValueHandles to track updates to the values that serve as SCEV keys. However, this still means that as we ran SCEV over each function in the module, we kept accumulating more and more SCEVs into the cache. At the end, we would have a SCEV cache with every value that we ever needed a SCEV for in the entire module!!! Yowzers. The releaseMemory routine would dump all of this, but that isn't realy called during normal runs of the pipeline as far as I can see. To make matters worse, there *is* actually a key that we don't update with value handles -- there is a map keyed off of Loop*s. Because LoopInfo *does* release its memory from run to run, it is entirely possible to run SCEV over one function, then over another function, and then lookup a Loop* from the second function but find an entry inserted for the first function! Ouch. To make matters still worse, there are plenty of updates that *don't* trip a value handle. It seems incredibly unlikely that today GVN or another pass that invalidates SCEV can update values in *just* such a way that a subsequent run of SCEV will incorrectly find lookups in a cache, but it is theoretically possible and would be a nightmare to debug. With this refactoring, I've fixed all this by actually destroying and recreating the ScalarEvolution object from run to run. Technically, this could increase the amount of malloc traffic we see, but then again it is also technically correct. ;] I don't actually think we're suffering from tons of malloc traffic from SCEV because if we were, the fact that we never clear the memory would seem more likely to have come up as an actual problem before now. So, I've made the simple fix here. If in fact there are serious issues with too much allocation and deallocation, I can work on a clever fix that preserves the allocations (while clearing the data) between each run, but I'd prefer to do that kind of optimization with a test case / benchmark that shows why we need such cleverness (and that can test that we actually make it faster). It's possible that this will make some things faster by making the SCEV caches have higher locality (due to being significantly smaller) so until there is a clear benchmark, I think the simple change is best. Differential Revision: http://reviews.llvm.org/D12063 llvm-svn: 245193
2015-08-17 10:08:17 +08:00
AU.addRequired<ScalarEvolutionWrapperPass>();
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
}
bool runOnFunction(Function &F) override;
bool runOnLoop(Loop *L);
void simplifyLoopLatch(Loop *L);
bool rotateLoop(Loop *L);
private:
PPCTargetMachine *TM;
LoopInfo *LI;
ScalarEvolution *SE;
};
Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) Apparently, the style needs to be agreed upon first. llvm-svn: 240390
2015-06-23 17:49:53 +08:00
}
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
char PPCLoopPreIncPrep::ID = 0;
Make helper functions/classes/globals static. NFC. llvm-svn: 228410
2015-02-07 01:51:54 +08:00
static const char *name = "Prepare loop for pre-inc. addressing modes";
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
INITIALIZE_PASS_BEGIN(PPCLoopPreIncPrep, DEBUG_TYPE, name, false, false)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
[PM] Port ScalarEvolution to the new pass manager. This change makes ScalarEvolution a stand-alone object and just produces one from a pass as needed. Making this work well requires making the object movable, using references instead of overwritten pointers in a number of places, and other refactorings. I've also wired it up to the new pass manager and added a RUN line to a test to exercise it under the new pass manager. This includes basic printing support much like with other analyses. But there is a big and somewhat scary change here. Prior to this patch ScalarEvolution was never *actually* invalidated!!! Re-running the pass just re-wired up the various other analyses and didn't remove any of the existing entries in the SCEV caches or clear out anything at all. This might seem OK as everything in SCEV that can uses ValueHandles to track updates to the values that serve as SCEV keys. However, this still means that as we ran SCEV over each function in the module, we kept accumulating more and more SCEVs into the cache. At the end, we would have a SCEV cache with every value that we ever needed a SCEV for in the entire module!!! Yowzers. The releaseMemory routine would dump all of this, but that isn't realy called during normal runs of the pipeline as far as I can see. To make matters worse, there *is* actually a key that we don't update with value handles -- there is a map keyed off of Loop*s. Because LoopInfo *does* release its memory from run to run, it is entirely possible to run SCEV over one function, then over another function, and then lookup a Loop* from the second function but find an entry inserted for the first function! Ouch. To make matters still worse, there are plenty of updates that *don't* trip a value handle. It seems incredibly unlikely that today GVN or another pass that invalidates SCEV can update values in *just* such a way that a subsequent run of SCEV will incorrectly find lookups in a cache, but it is theoretically possible and would be a nightmare to debug. With this refactoring, I've fixed all this by actually destroying and recreating the ScalarEvolution object from run to run. Technically, this could increase the amount of malloc traffic we see, but then again it is also technically correct. ;] I don't actually think we're suffering from tons of malloc traffic from SCEV because if we were, the fact that we never clear the memory would seem more likely to have come up as an actual problem before now. So, I've made the simple fix here. If in fact there are serious issues with too much allocation and deallocation, I can work on a clever fix that preserves the allocations (while clearing the data) between each run, but I'd prefer to do that kind of optimization with a test case / benchmark that shows why we need such cleverness (and that can test that we actually make it faster). It's possible that this will make some things faster by making the SCEV caches have higher locality (due to being significantly smaller) so until there is a clear benchmark, I think the simple change is best. Differential Revision: http://reviews.llvm.org/D12063 llvm-svn: 245193
2015-08-17 10:08:17 +08:00
INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
INITIALIZE_PASS_END(PPCLoopPreIncPrep, DEBUG_TYPE, name, false, false)
FunctionPass *llvm::createPPCLoopPreIncPrepPass(PPCTargetMachine &TM) {
return new PPCLoopPreIncPrep(TM);
}
namespace {
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
struct BucketElement {
BucketElement(const SCEVConstant *O, Instruction *I) : Offset(O), Instr(I) {}
BucketElement(Instruction *I) : Offset(nullptr), Instr(I) {}
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
const SCEVConstant *Offset;
Instruction *Instr;
};
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
struct Bucket {
Bucket(const SCEV *B, Instruction *I) : BaseSCEV(B),
Elements(1, BucketElement(I)) {}
const SCEV *BaseSCEV;
SmallVector<BucketElement, 16> Elements;
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
};
Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) Apparently, the style needs to be agreed upon first. llvm-svn: 240390
2015-06-23 17:49:53 +08:00
}
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
static bool IsPtrInBounds(Value *BasePtr) {
Value *StrippedBasePtr = BasePtr;
while (BitCastInst *BC = dyn_cast<BitCastInst>(StrippedBasePtr))
StrippedBasePtr = BC->getOperand(0);
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(StrippedBasePtr))
return GEP->isInBounds();
return false;
}
static Value *GetPointerOperand(Value *MemI) {
if (LoadInst *LMemI = dyn_cast<LoadInst>(MemI)) {
return LMemI->getPointerOperand();
} else if (StoreInst *SMemI = dyn_cast<StoreInst>(MemI)) {
return SMemI->getPointerOperand();
} else if (IntrinsicInst *IMemI = dyn_cast<IntrinsicInst>(MemI)) {
if (IMemI->getIntrinsicID() == Intrinsic::prefetch)
return IMemI->getArgOperand(0);
}
return 0;
}
bool PPCLoopPreIncPrep::runOnFunction(Function &F) {
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
[PM] Port ScalarEvolution to the new pass manager. This change makes ScalarEvolution a stand-alone object and just produces one from a pass as needed. Making this work well requires making the object movable, using references instead of overwritten pointers in a number of places, and other refactorings. I've also wired it up to the new pass manager and added a RUN line to a test to exercise it under the new pass manager. This includes basic printing support much like with other analyses. But there is a big and somewhat scary change here. Prior to this patch ScalarEvolution was never *actually* invalidated!!! Re-running the pass just re-wired up the various other analyses and didn't remove any of the existing entries in the SCEV caches or clear out anything at all. This might seem OK as everything in SCEV that can uses ValueHandles to track updates to the values that serve as SCEV keys. However, this still means that as we ran SCEV over each function in the module, we kept accumulating more and more SCEVs into the cache. At the end, we would have a SCEV cache with every value that we ever needed a SCEV for in the entire module!!! Yowzers. The releaseMemory routine would dump all of this, but that isn't realy called during normal runs of the pipeline as far as I can see. To make matters worse, there *is* actually a key that we don't update with value handles -- there is a map keyed off of Loop*s. Because LoopInfo *does* release its memory from run to run, it is entirely possible to run SCEV over one function, then over another function, and then lookup a Loop* from the second function but find an entry inserted for the first function! Ouch. To make matters still worse, there are plenty of updates that *don't* trip a value handle. It seems incredibly unlikely that today GVN or another pass that invalidates SCEV can update values in *just* such a way that a subsequent run of SCEV will incorrectly find lookups in a cache, but it is theoretically possible and would be a nightmare to debug. With this refactoring, I've fixed all this by actually destroying and recreating the ScalarEvolution object from run to run. Technically, this could increase the amount of malloc traffic we see, but then again it is also technically correct. ;] I don't actually think we're suffering from tons of malloc traffic from SCEV because if we were, the fact that we never clear the memory would seem more likely to have come up as an actual problem before now. So, I've made the simple fix here. If in fact there are serious issues with too much allocation and deallocation, I can work on a clever fix that preserves the allocations (while clearing the data) between each run, but I'd prefer to do that kind of optimization with a test case / benchmark that shows why we need such cleverness (and that can test that we actually make it faster). It's possible that this will make some things faster by making the SCEV caches have higher locality (due to being significantly smaller) so until there is a clear benchmark, I think the simple change is best. Differential Revision: http://reviews.llvm.org/D12063 llvm-svn: 245193
2015-08-17 10:08:17 +08:00
SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
bool MadeChange = false;
[PowerPC] Really iterate over all loops in PPCLoopDataPrefetch/PPCLoopPreIncPrep When I fixed these a couple of days ago to iterate over all loops, not just depth == 1 loops, I inadvertently made it such that we'd only look at the first top-level loop. Make sure that we really look at all of them. llvm-svn: 234705
2015-04-13 01:18:56 +08:00
for (auto I = LI->begin(), IE = LI->end(); I != IE; ++I)
for (auto L = df_begin(*I), LE = df_end(*I); L != LE; ++L)
MadeChange |= runOnLoop(*L);
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
return MadeChange;
}
bool PPCLoopPreIncPrep::runOnLoop(Loop *L) {
bool MadeChange = false;
// Only prep. the inner-most loop
if (!L->empty())
return MadeChange;
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
DEBUG(dbgs() << "PIP: Examining: " << *L << "\n");
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
BasicBlock *Header = L->getHeader();
const PPCSubtarget *ST =
TM ? TM->getSubtargetImpl(*Header->getParent()) : nullptr;
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
unsigned HeaderLoopPredCount =
std::distance(pred_begin(Header), pred_end(Header));
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
// Collect buckets of comparable addresses used by loads and stores.
SmallVector<Bucket, 16> Buckets;
for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
I != IE; ++I) {
for (BasicBlock::iterator J = (*I)->begin(), JE = (*I)->end();
J != JE; ++J) {
Value *PtrValue;
Instruction *MemI;
if (LoadInst *LMemI = dyn_cast<LoadInst>(J)) {
MemI = LMemI;
PtrValue = LMemI->getPointerOperand();
} else if (StoreInst *SMemI = dyn_cast<StoreInst>(J)) {
MemI = SMemI;
PtrValue = SMemI->getPointerOperand();
} else if (IntrinsicInst *IMemI = dyn_cast<IntrinsicInst>(J)) {
if (IMemI->getIntrinsicID() == Intrinsic::prefetch) {
MemI = IMemI;
PtrValue = IMemI->getArgOperand(0);
} else continue;
} else continue;
unsigned PtrAddrSpace = PtrValue->getType()->getPointerAddressSpace();
if (PtrAddrSpace)
continue;
// There are no update forms for Altivec vector load/stores.
if (ST && ST->hasAltivec() &&
PtrValue->getType()->getPointerElementType()->isVectorTy())
continue;
if (L->isLoopInvariant(PtrValue))
continue;
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
const SCEV *LSCEV = SE->getSCEVAtScope(PtrValue, L);
if (const SCEVAddRecExpr *LARSCEV = dyn_cast<SCEVAddRecExpr>(LSCEV)) {
if (LARSCEV->getLoop() != L)
continue;
} else {
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
continue;
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
}
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
bool FoundBucket = false;
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
for (auto &B : Buckets) {
const SCEV *Diff = SE->getMinusSCEV(LSCEV, B.BaseSCEV);
if (const auto *CDiff = dyn_cast<SCEVConstant>(Diff)) {
B.Elements.push_back(BucketElement(CDiff, MemI));
FoundBucket = true;
break;
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
}
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
}
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
if (!FoundBucket) {
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
if (Buckets.size() == MaxVars)
return MadeChange;
Buckets.push_back(Bucket(LSCEV, MemI));
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
}
}
}
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
if (Buckets.empty())
[PowerPC] Handle loop predecessor invokes If a loop predecessor has an invoke as its terminator, and the return value from that invoke is used to determine the loop iteration space, then we can't insert a computation based on that value in the loop predecessor prior to the terminator (oops). If there's such an invoke, or just no predecessor for that matter, insert a new loop preheader. llvm-svn: 228488
2015-02-07 15:32:58 +08:00
return MadeChange;
BasicBlock *LoopPredecessor = L->getLoopPredecessor();
// If there is no loop predecessor, or the loop predecessor's terminator
// returns a value (which might contribute to determining the loop's
// iteration space), insert a new preheader for the loop.
if (!LoopPredecessor ||
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
!LoopPredecessor->getTerminator()->getType()->isVoidTy()) {
[PowerPC] Handle loop predecessor invokes If a loop predecessor has an invoke as its terminator, and the return value from that invoke is used to determine the loop iteration space, then we can't insert a computation based on that value in the loop predecessor prior to the terminator (oops). If there's such an invoke, or just no predecessor for that matter, insert a new loop preheader. llvm-svn: 228488
2015-02-07 15:32:58 +08:00
LoopPredecessor = InsertPreheaderForLoop(L, this);
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
if (LoopPredecessor)
MadeChange = true;
}
[PowerPC] Handle loop predecessor invokes If a loop predecessor has an invoke as its terminator, and the return value from that invoke is used to determine the loop iteration space, then we can't insert a computation based on that value in the loop predecessor prior to the terminator (oops). If there's such an invoke, or just no predecessor for that matter, insert a new loop preheader. llvm-svn: 228488
2015-02-07 15:32:58 +08:00
if (!LoopPredecessor)
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
return MadeChange;
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
DEBUG(dbgs() << "PIP: Found " << Buckets.size() << " buckets\n");
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
SmallSet<BasicBlock *, 16> BBChanged;
for (unsigned i = 0, e = Buckets.size(); i != e; ++i) {
// The base address of each bucket is transformed into a phi and the others
// are rewritten as offsets of that variable.
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
// We have a choice now of which instruction's memory operand we use as the
// base for the generated PHI. Always picking the first instruction in each
// bucket does not work well, specifically because that instruction might
// be a prefetch (and there are no pre-increment dcbt variants). Otherwise,
// the choice is somewhat arbitrary, because the backend will happily
// generate direct offsets from both the pre-incremented and
// post-incremented pointer values. Thus, we'll pick the first non-prefetch
// instruction in each bucket, and adjust the recurrence and other offsets
// accordingly.
for (int j = 0, je = Buckets[i].Elements.size(); j != je; ++j) {
if (auto *II = dyn_cast<IntrinsicInst>(Buckets[i].Elements[j].Instr))
if (II->getIntrinsicID() == Intrinsic::prefetch)
continue;
// If we'd otherwise pick the first element anyway, there's nothing to do.
if (j == 0)
break;
// If our chosen element has no offset from the base pointer, there's
// nothing to do.
if (!Buckets[i].Elements[j].Offset ||
Buckets[i].Elements[j].Offset->isZero())
break;
const SCEV *Offset = Buckets[i].Elements[j].Offset;
Buckets[i].BaseSCEV = SE->getAddExpr(Buckets[i].BaseSCEV, Offset);
for (auto &E : Buckets[i].Elements) {
if (E.Offset)
E.Offset = cast<SCEVConstant>(SE->getMinusSCEV(E.Offset, Offset));
else
E.Offset = cast<SCEVConstant>(SE->getNegativeSCEV(Offset));
}
std::swap(Buckets[i].Elements[j], Buckets[i].Elements[0]);
break;
}
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
const SCEVAddRecExpr *BasePtrSCEV =
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
cast<SCEVAddRecExpr>(Buckets[i].BaseSCEV);
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
if (!BasePtrSCEV->isAffine())
continue;
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
DEBUG(dbgs() << "PIP: Transforming: " << *BasePtrSCEV << "\n");
assert(BasePtrSCEV->getLoop() == L &&
"AddRec for the wrong loop?");
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
// The instruction corresponding to the Bucket's BaseSCEV must be the first
// in the vector of elements.
Instruction *MemI = Buckets[i].Elements.begin()->Instr;
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
Value *BasePtr = GetPointerOperand(MemI);
assert(BasePtr && "No pointer operand");
[opaque pointer type] gep API migration llvm-svn: 232279
2015-03-15 05:20:51 +08:00
Type *I8Ty = Type::getInt8Ty(MemI->getParent()->getContext());
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
Type *I8PtrTy = Type::getInt8PtrTy(MemI->getParent()->getContext(),
BasePtr->getType()->getPointerAddressSpace());
const SCEV *BasePtrStartSCEV = BasePtrSCEV->getStart();
if (!SE->isLoopInvariant(BasePtrStartSCEV, L))
continue;
const SCEVConstant *BasePtrIncSCEV =
dyn_cast<SCEVConstant>(BasePtrSCEV->getStepRecurrence(*SE));
if (!BasePtrIncSCEV)
continue;
BasePtrStartSCEV = SE->getMinusSCEV(BasePtrStartSCEV, BasePtrIncSCEV);
if (!isSafeToExpand(BasePtrStartSCEV, *SE))
continue;
[PowerPC] Fix PPCLoopPreIncPrep for depth > 1 loops This pass had the same problem as the data-prefetching pass: it was only checking for depth == 1 loops in practice. Fix that, add some debugging statements, and make sure that, when we grab an AddRec, it is for the loop we expect. llvm-svn: 234670
2015-04-11 08:33:08 +08:00
DEBUG(dbgs() << "PIP: New start is: " << *BasePtrStartSCEV << "\n");
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
PHINode *NewPHI = PHINode::Create(I8PtrTy, HeaderLoopPredCount,
MemI->hasName() ? MemI->getName() + ".phi" : "",
Header->getFirstNonPHI());
DataLayout is mandatory, update the API to reflect it with references. Summary: Now that the DataLayout is a mandatory part of the module, let's start cleaning the codebase. This patch is a first attempt at doing that. This patch is not exactly NFC as for instance some places were passing a nullptr instead of the DataLayout, possibly just because there was a default value on the DataLayout argument to many functions in the API. Even though it is not purely NFC, there is no change in the validation. I turned as many pointer to DataLayout to references, this helped figuring out all the places where a nullptr could come up. I had initially a local version of this patch broken into over 30 independant, commits but some later commit were cleaning the API and touching part of the code modified in the previous commits, so it seemed cleaner without the intermediate state. Test Plan: Reviewers: echristo Subscribers: llvm-commits From: Mehdi Amini <mehdi.amini@apple.com> llvm-svn: 231740
2015-03-10 10:37:25 +08:00
SCEVExpander SCEVE(*SE, Header->getModule()->getDataLayout(), "pistart");
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
Value *BasePtrStart = SCEVE.expandCodeFor(BasePtrStartSCEV, I8PtrTy,
LoopPredecessor->getTerminator());
// Note that LoopPredecessor might occur in the predecessor list multiple
// times, and we need to add it the right number of times.
for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
PI != PE; ++PI) {
if (*PI != LoopPredecessor)
continue;
NewPHI->addIncoming(BasePtrStart, LoopPredecessor);
}
PowerPC: Remove implicit ilist iterator conversions, NFC llvm-svn: 250787
2015-10-20 09:07:37 +08:00
Instruction *InsPoint = &*Header->getFirstInsertionPt();
[opaque pointer type] gep API migration llvm-svn: 232279
2015-03-15 05:20:51 +08:00
GetElementPtrInst *PtrInc = GetElementPtrInst::Create(
I8Ty, NewPHI, BasePtrIncSCEV->getValue(),
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
MemI->hasName() ? MemI->getName() + ".inc" : "", InsPoint);
PtrInc->setIsInBounds(IsPtrInBounds(BasePtr));
for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
PI != PE; ++PI) {
if (*PI == LoopPredecessor)
continue;
NewPHI->addIncoming(PtrInc, *PI);
}
Instruction *NewBasePtr;
if (PtrInc->getType() != BasePtr->getType())
NewBasePtr = new BitCastInst(PtrInc, BasePtr->getType(),
PtrInc->hasName() ? PtrInc->getName() + ".cast" : "", InsPoint);
else
NewBasePtr = PtrInc;
if (Instruction *IDel = dyn_cast<Instruction>(BasePtr))
BBChanged.insert(IDel->getParent());
BasePtr->replaceAllUsesWith(NewBasePtr);
RecursivelyDeleteTriviallyDeadInstructions(BasePtr);
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
// Keep track of the replacement pointer values we've inserted so that we
// don't generate more pointer values than necessary.
SmallPtrSet<Value *, 16> NewPtrs;
NewPtrs.insert( NewBasePtr);
for (auto I = std::next(Buckets[i].Elements.begin()),
IE = Buckets[i].Elements.end(); I != IE; ++I) {
Value *Ptr = GetPointerOperand(I->Instr);
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
assert(Ptr && "No pointer operand");
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
if (NewPtrs.count(Ptr))
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
continue;
Instruction *RealNewPtr;
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
if (!I->Offset || I->Offset->getValue()->isZero()) {
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
RealNewPtr = NewBasePtr;
} else {
Instruction *PtrIP = dyn_cast<Instruction>(Ptr);
if (PtrIP && isa<Instruction>(NewBasePtr) &&
cast<Instruction>(NewBasePtr)->getParent() == PtrIP->getParent())
PtrIP = 0;
else if (isa<PHINode>(PtrIP))
PowerPC: Remove implicit ilist iterator conversions, NFC llvm-svn: 250787
2015-10-20 09:07:37 +08:00
PtrIP = &*PtrIP->getParent()->getFirstInsertionPt();
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
else if (!PtrIP)
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
PtrIP = I->Instr;
[opaque pointer type] gep API migration llvm-svn: 232279
2015-03-15 05:20:51 +08:00
GetElementPtrInst *NewPtr = GetElementPtrInst::Create(
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
I8Ty, PtrInc, I->Offset->getValue(),
I->Instr->hasName() ? I->Instr->getName() + ".off" : "", PtrIP);
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
if (!PtrIP)
NewPtr->insertAfter(cast<Instruction>(PtrInc));
NewPtr->setIsInBounds(IsPtrInBounds(Ptr));
RealNewPtr = NewPtr;
}
if (Instruction *IDel = dyn_cast<Instruction>(Ptr))
BBChanged.insert(IDel->getParent());
Instruction *ReplNewPtr;
if (Ptr->getType() != RealNewPtr->getType()) {
ReplNewPtr = new BitCastInst(RealNewPtr, Ptr->getType(),
Ptr->hasName() ? Ptr->getName() + ".cast" : "");
ReplNewPtr->insertAfter(RealNewPtr);
} else
ReplNewPtr = RealNewPtr;
Ptr->replaceAllUsesWith(ReplNewPtr);
RecursivelyDeleteTriviallyDeadInstructions(Ptr);
[PowerPC] Fix LoopPreIncPrep not to depend on SCEV constant simplifications Under most circumstances, if SCEV can simplify X-Y to a constant, then it can also simplify Y-X to a constant. However, there is no guarantee that this is always true, and concensus is not to consider that a correctness bug in SCEV (although it is undesirable). PPCLoopPreIncPrep gathers pointers used to access memory (via loads, stores and prefetches) into buckets, where in each bucket the relative pointer offsets are constant. We used to keep each bucket as a multimap, where SCEV's subtraction operation was used to define the ordering predicate. Instead, use a fixed SCEV base expression for each bucket, record the constant offsets from that base expression, and adjust it later, if desirable, once all pointers have been collected. Doing it this way should be more compile-time efficient than the previous scheme (in addition to making the implementation less sensitive to SCEV simplification quirks). Fixes PR25170. llvm-svn: 252417
2015-11-08 16:04:40 +08:00
NewPtrs.insert(RealNewPtr);
[PowerPC] Prepare loops for pre-increment loads/stores PowerPC supports pre-increment load/store instructions (except for Altivec/VSX vector load/stores). Using these on embedded cores can be very important, but most loops are not naturally set up to use them. We can often change that, however, by placing loops into a non-canonical form. Generically, this means transforming loops like this: for (int i = 0; i < n; ++i) array[i] = c; to look like this: T *p = array[-1]; for (int i = 0; i < n; ++i) *++p = c; the key point is that addresses accessed are pulled into dedicated PHIs and "pre-decremented" in the loop preheader. This allows the use of pre-increment load/store instructions without loop peeling. A target-specific late IR-level pass (running post-LSR), PPCLoopPreIncPrep, is introduced to perform this transformation. I've used this code out-of-tree for generating code for the PPC A2 for over a year. Somewhat to my surprise, running the test suite + externals on a P7 with this transformation enabled showed no performance regressions, and one speedup: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk -2.32514% +/- 1.03736% So I'm going to enable it on everything for now. I was surprised by this because, on the POWER cores, these pre-increment load/store instructions are cracked (and, thus, harder to schedule effectively). But seeing no regressions, and feeling that it is generally easier to split instructions apart late than it is to combine them late, this might be the better approach regardless. In the future, we might want to integrate this functionality into LSR (but currently LSR does not create new PHI nodes, so (for that and other reasons) significant work would need to be done). llvm-svn: 228328
2015-02-06 02:43:00 +08:00
}
MadeChange = true;
}
for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
I != IE; ++I) {
if (BBChanged.count(*I))
DeleteDeadPHIs(*I);
}
return MadeChange;
}