llvm-project/llvm/lib/Transforms/Scalar/Scalar.cpp

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//===-- Scalar.cpp --------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
2012-07-24 18:51:42 +08:00
// This file implements common infrastructure for libLLVMScalarOpts.a, which
// implements several scalar transformations over the LLVM intermediate
// representation, including the C bindings for that library.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
#include "llvm-c/Initialization.h"
#include "llvm-c/Transforms/Scalar.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/ScopedNoAliasAA.h"
#include "llvm/Analysis/TypeBasedAliasAnalysis.h"
#include "llvm/Transforms/Scalar/GVN.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/IR/LegacyPassManager.h"
using namespace llvm;
2012-07-24 18:51:42 +08:00
/// initializeScalarOptsPasses - Initialize all passes linked into the
/// ScalarOpts library.
void llvm::initializeScalarOpts(PassRegistry &Registry) {
initializeADCELegacyPassPass(Registry);
[BDCE] Add a bit-tracking DCE pass BDCE is a bit-tracking dead code elimination pass. It is based on ADCE (the "aggressive DCE" pass), with the added capability to track dead bits of integer valued instructions and remove those instructions when all of the bits are dead. Currently, it does not actually do this all-bits-dead removal, but rather replaces the instruction's uses with a constant zero, and lets instcombine (and the later run of ADCE) do the rest. Because we essentially get a run of ADCE "for free" while tracking the dead bits, we also do what ADCE does and removes actually-dead instructions as well (this includes instructions newly trivially dead because all bits were dead, but not all such instructions can be removed). The motivation for this is a case like: int __attribute__((const)) foo(int i); int bar(int x) { x |= (4 & foo(5)); x |= (8 & foo(3)); x |= (16 & foo(2)); x |= (32 & foo(1)); x |= (64 & foo(0)); x |= (128& foo(4)); return x >> 4; } As it turns out, if you order the bit-field insertions so that all of the dead ones come last, then instcombine will remove them. However, if you pick some other order (such as the one above), the fact that some of the calls to foo() are useless is not locally obvious, and we don't remove them (without this pass). I did a quick compile-time overhead check using sqlite from the test suite (Release+Asserts). BDCE took ~0.4% of the compilation time (making it about twice as expensive as ADCE). I've not looked at why yet, but we eliminate instructions due to having all-dead bits in: External/SPEC/CFP2006/447.dealII/447.dealII External/SPEC/CINT2006/400.perlbench/400.perlbench External/SPEC/CINT2006/403.gcc/403.gcc MultiSource/Applications/ClamAV/clamscan MultiSource/Benchmarks/7zip/7zip-benchmark llvm-svn: 229462
2015-02-17 09:36:59 +08:00
initializeBDCEPass(Registry);
initializeAlignmentFromAssumptionsPass(Registry);
initializeConstantHoistingPass(Registry);
initializeConstantPropagationPass(Registry);
initializeCorrelatedValuePropagationPass(Registry);
initializeDCELegacyPassPass(Registry);
initializeDeadInstEliminationPass(Registry);
initializeScalarizerPass(Registry);
initializeDSEPass(Registry);
initializeGVNLegacyPassPass(Registry);
initializeEarlyCSELegacyPassPass(Registry);
initializeFlattenCFGPassPass(Registry);
initializeInductiveRangeCheckEliminationPass(Registry);
initializeIndVarSimplifyPass(Registry);
initializeJumpThreadingPass(Registry);
initializeLICMPass(Registry);
initializeLoopDataPrefetchPass(Registry);
initializeLoopDeletionPass(Registry);
initializeLoopAccessAnalysisPass(Registry);
initializeLoopInstSimplifyPass(Registry);
initializeLoopInterchangePass(Registry);
initializeLoopRotateLegacyPassPass(Registry);
initializeLoopStrengthReducePass(Registry);
Add a loop rerolling pass This adds a loop rerolling pass: the opposite of (partial) loop unrolling. The transformation aims to take loops like this: for (int i = 0; i < 3200; i += 5) { a[i] += alpha * b[i]; a[i + 1] += alpha * b[i + 1]; a[i + 2] += alpha * b[i + 2]; a[i + 3] += alpha * b[i + 3]; a[i + 4] += alpha * b[i + 4]; } and turn them into this: for (int i = 0; i < 3200; ++i) { a[i] += alpha * b[i]; } and loops like this: for (int i = 0; i < 500; ++i) { x[3*i] = foo(0); x[3*i+1] = foo(0); x[3*i+2] = foo(0); } and turn them into this: for (int i = 0; i < 1500; ++i) { x[i] = foo(0); } There are two motivations for this transformation: 1. Code-size reduction (especially relevant, obviously, when compiling for code size). 2. Providing greater choice to the loop vectorizer (and generic unroller) to choose the unrolling factor (and a better ability to vectorize). The loop vectorizer can take vector lengths and register pressure into account when choosing an unrolling factor, for example, and a pre-unrolled loop limits that choice. This is especially problematic if the manual unrolling was optimized for a machine different from the current target. The current implementation is limited to single basic-block loops only. The rerolling recognition should work regardless of how the loop iterations are intermixed within the loop body (subject to dependency and side-effect constraints), but the significant restriction is that the order of the instructions in each iteration must be identical. This seems sufficient to capture all current use cases. This pass is not currently enabled by default at any optimization level. llvm-svn: 194939
2013-11-17 07:59:05 +08:00
initializeLoopRerollPass(Registry);
initializeLoopUnrollPass(Registry);
initializeLoopUnswitchPass(Registry);
initializeLoopVersioningLICMPass(Registry);
initializeLoopIdiomRecognizePass(Registry);
initializeLowerAtomicPass(Registry);
initializeLowerExpectIntrinsicPass(Registry);
initializeLowerGuardIntrinsicPass(Registry);
initializeMemCpyOptPass(Registry);
initializeMergedLoadStoreMotionPass(Registry);
initializeNaryReassociatePass(Registry);
initializePartiallyInlineLibCallsPass(Registry);
initializeReassociateLegacyPassPass(Registry);
initializeRegToMemPass(Registry);
Add a pass for constructing gc.statepoint sequences w/explicit relocations This patch consists of a single pass whose only purpose is to visit previous inserted gc.statepoints which do not have gc.relocates inserted yet, and insert them. This can be used either immediately after IR generation to perform 'early safepoint insertion' or late in the pass order to perform 'late insertion'. This patch is setting the stage for work to continue in tree. In particular, there are known naming and style violations in the current patch. I'll try to get those resolved over the next week or so. As I touch each area to make style changes, I need to make sure we have adequate testing in place. As part of the cleanup, I will be cleaning up a collection of test cases we have out of tree and submitting them upstream. The tests included in this change are very basic and mostly to provide examples of usage. The pass has several main subproblems it needs to address: - First, it has identify any live pointers. In the current code, the use of address spaces to distinguish pointers to GC managed objects is hard coded, but this will become parametrizable in the near future. Note that the current change doesn't actually contain a useful liveness analysis. It was seperated into a followup change as the code wasn't ready to be shared. Instead, the current implementation just considers any dominating def of appropriate pointer type to be live. - Second, it has to identify base pointers for each live pointer. This is a fairly straight forward data flow algorithm. - Third, the information in the previous steps is used to actually introduce rewrites. Rather than trying to do this by hand, we simply re-purpose the code behind Mem2Reg to do this for us. llvm-svn: 229945
2015-02-20 09:06:44 +08:00
initializeRewriteStatepointsForGCPass(Registry);
initializeSCCPPass(Registry);
initializeIPSCCPPass(Registry);
[PM] Port SROA to the new pass manager. In some ways this is a very boring port to the new pass manager as there are no interesting analyses or dependencies or other oddities. However, this does introduce the first good example of a transformation pass with non-trivial state porting to the new pass manager. I've tried to carve out patterns here to replicate elsewhere, and would appreciate comments on whether folks like these patterns: - A common need in the new pass manager is to effectively lift the pass class and some of its state into a public header file. Prior to this, LLVM used anonymous namespaces to provide "module private" types and utilities, but that doesn't scale to cases where a public header file is needed and the new pass manager will exacerbate that. The pattern I've adopted here is to use the namespace-cased-name of the core pass (what would be a module if we had them) as a module-private namespace. Then utility and other code can be declared and defined in this namespace. At some point in the future, we could even have (conditionally compiled) code that used modules features when available to do the same basic thing. - I've split the actual pass run method in two in order to expose a private method usable by the old pass manager to wrap the new class with a minimum of duplicated code. I actually looked at a bunch of ways to automate or generate these, but they are all quite terrible IMO. The fundamental need is to extract the set of analyses which need to cross this interface boundary, and that will end up being too unpredictable to effectively encapsulate IMO. This is also a relatively small amount of boiler plate that will live a relatively short time, so I'm not too worried about the fact that it is boiler plate. The rest of the patch is totally boring but results in a massive diff (sorry). It just moves code around and removes or adds qualifiers to reflect the new name and nesting structure. Differential Revision: http://reviews.llvm.org/D12773 llvm-svn: 247501
2015-09-12 17:09:14 +08:00
initializeSROALegacyPassPass(Registry);
initializeSROA_DTPass(Registry);
initializeSROA_SSAUpPass(Registry);
initializeCFGSimplifyPassPass(Registry);
initializeStructurizeCFGPass(Registry);
initializeSinkingLegacyPassPass(Registry);
initializeTailCallElimPass(Registry);
initializeSeparateConstOffsetFromGEPPass(Registry);
initializeSpeculativeExecutionPass(Registry);
initializeStraightLineStrengthReducePass(Registry);
initializeLoadCombinePass(Registry);
Add a pass for inserting safepoints into (nearly) arbitrary IR This pass is responsible for figuring out where to place call safepoints and safepoint polls. It doesn't actually make the relocations explicit; that's the job of the RewriteStatepointsForGC pass (http://reviews.llvm.org/D6975). Note that this code is not yet finalized. Its moving in tree for incremental development, but further cleanup is needed and will happen over the next few days. It is not yet part of the standard pass order. Planned changes in the near future: - I plan on restructuring the statepoint rewrite to use the functions add to the IRBuilder a while back. - In the current pass, the function "gc.safepoint_poll" is treated specially but is not an intrinsic. I plan to make identifying the poll function a property of the GCStrategy at some point in the near future. - As follow on patches, I will be separating a collection of test cases we have out of tree and submitting them upstream. - It's not explicit in the code, but these two patches are introducing a new state for a statepoint which looks a lot like a patchpoint. There's no a transient form which doesn't yet have the relocations explicitly represented, but does prevent reordering of memory operations. Once this is in, I need to update actually make this explicit by reserving the 'unused' argument of the statepoint as a flag, updating the docs, and making the code explicitly check for such a thing. This wasn't really planned, but once I split the two passes - which was done for other reasons - the intermediate state fell out. Just reminds us once again that we need to merge statepoints and patchpoints at some point in the not that distant future. Future directions planned: - Identifying more cases where a backedge safepoint isn't required to ensure timely execution of a safepoint poll. - Tweaking the insertion process to generate easier to optimize IR. (For example, investigating making SplitBackedge) the default. - Adding opt-in flags for a GCStrategy to use this pass. Once done, add this pass to the actual pass ordering. Differential Revision: http://reviews.llvm.org/D6981 llvm-svn: 228090
2015-02-04 08:37:33 +08:00
initializePlaceBackedgeSafepointsImplPass(Registry);
initializePlaceSafepointsPass(Registry);
initializeFloat2IntPass(Registry);
initializeLoopDistributePass(Registry);
LLE 6/6: Add LoopLoadElimination pass Summary: The goal of this pass is to perform store-to-load forwarding across the backedge of a loop. E.g.: for (i) A[i + 1] = A[i] + B[i] => T = A[0] for (i) T = T + B[i] A[i + 1] = T The pass relies on loop dependence analysis via LoopAccessAnalisys to find opportunities of loop-carried dependences with a distance of one between a store and a load. Since it's using LoopAccessAnalysis, it was easy to also add support for versioning away may-aliasing intervening stores that would otherwise prevent this transformation. This optimization is also performed by Load-PRE in GVN without the option of multi-versioning. As was discussed with Daniel Berlin in http://reviews.llvm.org/D9548, this is inferior to a more loop-aware solution applied here. Hopefully, we will be able to remove some complexity from GVN/MemorySSA as a consequence. In the long run, we may want to extend this pass (or create a new one if there is little overlap) to also eliminate loop-indepedent redundant loads and store that *require* versioning due to may-aliasing intervening stores/loads. I have some motivating cases for store elimination. My plan right now is to wait for MemorySSA to come online first rather than using memdep for this. The main motiviation for this pass is the 456.hmmer loop in SPECint2006 where after distributing the original loop and vectorizing the top part, we are left with the critical path exposed in the bottom loop. Being able to promote the memory dependence into a register depedence (even though the HW does perform store-to-load fowarding as well) results in a major gain (~20%). This gain also transfers over to x86: it's around 8-10%. Right now the pass is off by default and can be enabled with -enable-loop-load-elim. On the LNT testsuite, there are two performance changes (negative number -> improvement): 1. -28% in Polybench/linear-algebra/solvers/dynprog: the length of the critical paths is reduced 2. +2% in Polybench/stencils/adi: Unfortunately, I couldn't reproduce this outside of LNT The pass is scheduled after the loop vectorizer (which is after loop distribution). The rational is to try to reuse LAA state, rather than recomputing it. The order between LV and LLE is not critical because normally LV does not touch scalar st->ld forwarding cases where vectorizing would inhibit the CPU's st->ld forwarding to kick in. LoopLoadElimination requires LAA to provide the full set of dependences (including forward dependences). LAA is known to omit loop-independent dependences in certain situations. The big comment before removeDependencesFromMultipleStores explains why this should not occur for the cases that we're interested in. Reviewers: dberlin, hfinkel Subscribers: junbuml, dberlin, mssimpso, rengolin, sanjoy, llvm-commits Differential Revision: http://reviews.llvm.org/D13259 llvm-svn: 252017
2015-11-04 07:50:08 +08:00
initializeLoopLoadEliminationPass(Registry);
initializeLoopSimplifyCFGLegacyPassPass(Registry);
initializeLoopVersioningPassPass(Registry);
}
void LLVMInitializeScalarOpts(LLVMPassRegistryRef R) {
initializeScalarOpts(*unwrap(R));
}
void LLVMAddAggressiveDCEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createAggressiveDCEPass());
}
[BDCE] Add a bit-tracking DCE pass BDCE is a bit-tracking dead code elimination pass. It is based on ADCE (the "aggressive DCE" pass), with the added capability to track dead bits of integer valued instructions and remove those instructions when all of the bits are dead. Currently, it does not actually do this all-bits-dead removal, but rather replaces the instruction's uses with a constant zero, and lets instcombine (and the later run of ADCE) do the rest. Because we essentially get a run of ADCE "for free" while tracking the dead bits, we also do what ADCE does and removes actually-dead instructions as well (this includes instructions newly trivially dead because all bits were dead, but not all such instructions can be removed). The motivation for this is a case like: int __attribute__((const)) foo(int i); int bar(int x) { x |= (4 & foo(5)); x |= (8 & foo(3)); x |= (16 & foo(2)); x |= (32 & foo(1)); x |= (64 & foo(0)); x |= (128& foo(4)); return x >> 4; } As it turns out, if you order the bit-field insertions so that all of the dead ones come last, then instcombine will remove them. However, if you pick some other order (such as the one above), the fact that some of the calls to foo() are useless is not locally obvious, and we don't remove them (without this pass). I did a quick compile-time overhead check using sqlite from the test suite (Release+Asserts). BDCE took ~0.4% of the compilation time (making it about twice as expensive as ADCE). I've not looked at why yet, but we eliminate instructions due to having all-dead bits in: External/SPEC/CFP2006/447.dealII/447.dealII External/SPEC/CINT2006/400.perlbench/400.perlbench External/SPEC/CINT2006/403.gcc/403.gcc MultiSource/Applications/ClamAV/clamscan MultiSource/Benchmarks/7zip/7zip-benchmark llvm-svn: 229462
2015-02-17 09:36:59 +08:00
void LLVMAddBitTrackingDCEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createBitTrackingDCEPass());
}
void LLVMAddAlignmentFromAssumptionsPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createAlignmentFromAssumptionsPass());
}
void LLVMAddCFGSimplificationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createCFGSimplificationPass());
}
void LLVMAddDeadStoreEliminationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createDeadStoreEliminationPass());
}
void LLVMAddScalarizerPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createScalarizerPass());
}
void LLVMAddGVNPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createGVNPass());
}
void LLVMAddMergedLoadStoreMotionPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createMergedLoadStoreMotionPass());
}
void LLVMAddIndVarSimplifyPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createIndVarSimplifyPass());
}
void LLVMAddInstructionCombiningPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createInstructionCombiningPass());
}
void LLVMAddJumpThreadingPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createJumpThreadingPass());
}
void LLVMAddLICMPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLICMPass());
}
void LLVMAddLoopDeletionPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopDeletionPass());
}
void LLVMAddLoopIdiomPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopIdiomPass());
}
void LLVMAddLoopRotatePass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopRotatePass());
}
Add a loop rerolling pass This adds a loop rerolling pass: the opposite of (partial) loop unrolling. The transformation aims to take loops like this: for (int i = 0; i < 3200; i += 5) { a[i] += alpha * b[i]; a[i + 1] += alpha * b[i + 1]; a[i + 2] += alpha * b[i + 2]; a[i + 3] += alpha * b[i + 3]; a[i + 4] += alpha * b[i + 4]; } and turn them into this: for (int i = 0; i < 3200; ++i) { a[i] += alpha * b[i]; } and loops like this: for (int i = 0; i < 500; ++i) { x[3*i] = foo(0); x[3*i+1] = foo(0); x[3*i+2] = foo(0); } and turn them into this: for (int i = 0; i < 1500; ++i) { x[i] = foo(0); } There are two motivations for this transformation: 1. Code-size reduction (especially relevant, obviously, when compiling for code size). 2. Providing greater choice to the loop vectorizer (and generic unroller) to choose the unrolling factor (and a better ability to vectorize). The loop vectorizer can take vector lengths and register pressure into account when choosing an unrolling factor, for example, and a pre-unrolled loop limits that choice. This is especially problematic if the manual unrolling was optimized for a machine different from the current target. The current implementation is limited to single basic-block loops only. The rerolling recognition should work regardless of how the loop iterations are intermixed within the loop body (subject to dependency and side-effect constraints), but the significant restriction is that the order of the instructions in each iteration must be identical. This seems sufficient to capture all current use cases. This pass is not currently enabled by default at any optimization level. llvm-svn: 194939
2013-11-17 07:59:05 +08:00
void LLVMAddLoopRerollPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopRerollPass());
}
void LLVMAddLoopSimplifyCFGPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopSimplifyCFGPass());
}
void LLVMAddLoopUnrollPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopUnrollPass());
}
void LLVMAddLoopUnswitchPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopUnswitchPass());
}
void LLVMAddMemCpyOptPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createMemCpyOptPass());
}
void LLVMAddPartiallyInlineLibCallsPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createPartiallyInlineLibCallsPass());
}
void LLVMAddLowerSwitchPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLowerSwitchPass());
}
void LLVMAddPromoteMemoryToRegisterPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createPromoteMemoryToRegisterPass());
}
void LLVMAddReassociatePass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createReassociatePass());
}
void LLVMAddSCCPPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createSCCPPass());
}
void LLVMAddScalarReplAggregatesPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createScalarReplAggregatesPass());
}
void LLVMAddScalarReplAggregatesPassSSA(LLVMPassManagerRef PM) {
unwrap(PM)->add(createScalarReplAggregatesPass(-1, false));
}
void LLVMAddScalarReplAggregatesPassWithThreshold(LLVMPassManagerRef PM,
int Threshold) {
unwrap(PM)->add(createScalarReplAggregatesPass(Threshold));
}
void LLVMAddSimplifyLibCallsPass(LLVMPassManagerRef PM) {
// NOTE: The simplify-libcalls pass has been removed.
}
void LLVMAddTailCallEliminationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createTailCallEliminationPass());
}
void LLVMAddConstantPropagationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createConstantPropagationPass());
}
void LLVMAddDemoteMemoryToRegisterPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createDemoteRegisterToMemoryPass());
}
void LLVMAddVerifierPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createVerifierPass());
}
void LLVMAddCorrelatedValuePropagationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createCorrelatedValuePropagationPass());
}
void LLVMAddEarlyCSEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createEarlyCSEPass());
}
void LLVMAddTypeBasedAliasAnalysisPass(LLVMPassManagerRef PM) {
[PM/AA] Rebuild LLVM's alias analysis infrastructure in a way compatible with the new pass manager, and no longer relying on analysis groups. This builds essentially a ground-up new AA infrastructure stack for LLVM. The core ideas are the same that are used throughout the new pass manager: type erased polymorphism and direct composition. The design is as follows: - FunctionAAResults is a type-erasing alias analysis results aggregation interface to walk a single query across a range of results from different alias analyses. Currently this is function-specific as we always assume that aliasing queries are *within* a function. - AAResultBase is a CRTP utility providing stub implementations of various parts of the alias analysis result concept, notably in several cases in terms of other more general parts of the interface. This can be used to implement only a narrow part of the interface rather than the entire interface. This isn't really ideal, this logic should be hoisted into FunctionAAResults as currently it will cause a significant amount of redundant work, but it faithfully models the behavior of the prior infrastructure. - All the alias analysis passes are ported to be wrapper passes for the legacy PM and new-style analysis passes for the new PM with a shared result object. In some cases (most notably CFL), this is an extremely naive approach that we should revisit when we can specialize for the new pass manager. - BasicAA has been restructured to reflect that it is much more fundamentally a function analysis because it uses dominator trees and loop info that need to be constructed for each function. All of the references to getting alias analysis results have been updated to use the new aggregation interface. All the preservation and other pass management code has been updated accordingly. The way the FunctionAAResultsWrapperPass works is to detect the available alias analyses when run, and add them to the results object. This means that we should be able to continue to respect when various passes are added to the pipeline, for example adding CFL or adding TBAA passes should just cause their results to be available and to get folded into this. The exception to this rule is BasicAA which really needs to be a function pass due to using dominator trees and loop info. As a consequence, the FunctionAAResultsWrapperPass directly depends on BasicAA and always includes it in the aggregation. This has significant implications for preserving analyses. Generally, most passes shouldn't bother preserving FunctionAAResultsWrapperPass because rebuilding the results just updates the set of known AA passes. The exception to this rule are LoopPass instances which need to preserve all the function analyses that the loop pass manager will end up needing. This means preserving both BasicAAWrapperPass and the aggregating FunctionAAResultsWrapperPass. Now, when preserving an alias analysis, you do so by directly preserving that analysis. This is only necessary for non-immutable-pass-provided alias analyses though, and there are only three of interest: BasicAA, GlobalsAA (formerly GlobalsModRef), and SCEVAA. Usually BasicAA is preserved when needed because it (like DominatorTree and LoopInfo) is marked as a CFG-only pass. I've expanded GlobalsAA into the preserved set everywhere we previously were preserving all of AliasAnalysis, and I've added SCEVAA in the intersection of that with where we preserve SCEV itself. One significant challenge to all of this is that the CGSCC passes were actually using the alias analysis implementations by taking advantage of a pretty amazing set of loop holes in the old pass manager's analysis management code which allowed analysis groups to slide through in many cases. Moving away from analysis groups makes this problem much more obvious. To fix it, I've leveraged the flexibility the design of the new PM components provides to just directly construct the relevant alias analyses for the relevant functions in the IPO passes that need them. This is a bit hacky, but should go away with the new pass manager, and is already in many ways cleaner than the prior state. Another significant challenge is that various facilities of the old alias analysis infrastructure just don't fit any more. The most significant of these is the alias analysis 'counter' pass. That pass relied on the ability to snoop on AA queries at different points in the analysis group chain. Instead, I'm planning to build printing functionality directly into the aggregation layer. I've not included that in this patch merely to keep it smaller. Note that all of this needs a nearly complete rewrite of the AA documentation. I'm planning to do that, but I'd like to make sure the new design settles, and to flesh out a bit more of what it looks like in the new pass manager first. Differential Revision: http://reviews.llvm.org/D12080 llvm-svn: 247167
2015-09-10 01:55:00 +08:00
unwrap(PM)->add(createTypeBasedAAWrapperPass());
}
Add scoped-noalias metadata This commit adds scoped noalias metadata. The primary motivations for this feature are: 1. To preserve noalias function attribute information when inlining 2. To provide the ability to model block-scope C99 restrict pointers Neither of these two abilities are added here, only the necessary infrastructure. In fact, there should be no change to existing functionality, only the addition of new features. The logic that converts noalias function parameters into this metadata during inlining will come in a follow-up commit. What is added here is the ability to generally specify noalias memory-access sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA nodes: !scope0 = metadata !{ metadata !"scope of foo()" } !scope1 = metadata !{ metadata !"scope 1", metadata !scope0 } !scope2 = metadata !{ metadata !"scope 2", metadata !scope0 } !scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 } !scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 } Loads and stores can be tagged with an alias-analysis scope, and also, with a noalias tag for a specific scope: ... = load %ptr1, !alias.scope !{ !scope1 } ... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 } When evaluating an aliasing query, if one of the instructions is associated with an alias.scope id that is identical to the noalias scope associated with the other instruction, or is a descendant (in the scope hierarchy) of the noalias scope associated with the other instruction, then the two memory accesses are assumed not to alias. Note that is the first element of the scope metadata is a string, then it can be combined accross functions and translation units. The string can be replaced by a self-reference to create globally unqiue scope identifiers. [Note: This overview is slightly stylized, since the metadata nodes really need to just be numbers (!0 instead of !scope0), and the scope lists are also global unnamed metadata.] Existing noalias metadata in a callee is "cloned" for use by the inlined code. This is necessary because the aliasing scopes are unique to each call site (because of possible control dependencies on the aliasing properties). For example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } -- now just because we know that a1 does not alias with b1 at the first call site, and a2 does not alias with b2 at the second call site, we cannot let inlining these functons have the metadata imply that a1 does not alias with b2. llvm-svn: 213864
2014-07-24 22:25:39 +08:00
void LLVMAddScopedNoAliasAAPass(LLVMPassManagerRef PM) {
[PM/AA] Rebuild LLVM's alias analysis infrastructure in a way compatible with the new pass manager, and no longer relying on analysis groups. This builds essentially a ground-up new AA infrastructure stack for LLVM. The core ideas are the same that are used throughout the new pass manager: type erased polymorphism and direct composition. The design is as follows: - FunctionAAResults is a type-erasing alias analysis results aggregation interface to walk a single query across a range of results from different alias analyses. Currently this is function-specific as we always assume that aliasing queries are *within* a function. - AAResultBase is a CRTP utility providing stub implementations of various parts of the alias analysis result concept, notably in several cases in terms of other more general parts of the interface. This can be used to implement only a narrow part of the interface rather than the entire interface. This isn't really ideal, this logic should be hoisted into FunctionAAResults as currently it will cause a significant amount of redundant work, but it faithfully models the behavior of the prior infrastructure. - All the alias analysis passes are ported to be wrapper passes for the legacy PM and new-style analysis passes for the new PM with a shared result object. In some cases (most notably CFL), this is an extremely naive approach that we should revisit when we can specialize for the new pass manager. - BasicAA has been restructured to reflect that it is much more fundamentally a function analysis because it uses dominator trees and loop info that need to be constructed for each function. All of the references to getting alias analysis results have been updated to use the new aggregation interface. All the preservation and other pass management code has been updated accordingly. The way the FunctionAAResultsWrapperPass works is to detect the available alias analyses when run, and add them to the results object. This means that we should be able to continue to respect when various passes are added to the pipeline, for example adding CFL or adding TBAA passes should just cause their results to be available and to get folded into this. The exception to this rule is BasicAA which really needs to be a function pass due to using dominator trees and loop info. As a consequence, the FunctionAAResultsWrapperPass directly depends on BasicAA and always includes it in the aggregation. This has significant implications for preserving analyses. Generally, most passes shouldn't bother preserving FunctionAAResultsWrapperPass because rebuilding the results just updates the set of known AA passes. The exception to this rule are LoopPass instances which need to preserve all the function analyses that the loop pass manager will end up needing. This means preserving both BasicAAWrapperPass and the aggregating FunctionAAResultsWrapperPass. Now, when preserving an alias analysis, you do so by directly preserving that analysis. This is only necessary for non-immutable-pass-provided alias analyses though, and there are only three of interest: BasicAA, GlobalsAA (formerly GlobalsModRef), and SCEVAA. Usually BasicAA is preserved when needed because it (like DominatorTree and LoopInfo) is marked as a CFG-only pass. I've expanded GlobalsAA into the preserved set everywhere we previously were preserving all of AliasAnalysis, and I've added SCEVAA in the intersection of that with where we preserve SCEV itself. One significant challenge to all of this is that the CGSCC passes were actually using the alias analysis implementations by taking advantage of a pretty amazing set of loop holes in the old pass manager's analysis management code which allowed analysis groups to slide through in many cases. Moving away from analysis groups makes this problem much more obvious. To fix it, I've leveraged the flexibility the design of the new PM components provides to just directly construct the relevant alias analyses for the relevant functions in the IPO passes that need them. This is a bit hacky, but should go away with the new pass manager, and is already in many ways cleaner than the prior state. Another significant challenge is that various facilities of the old alias analysis infrastructure just don't fit any more. The most significant of these is the alias analysis 'counter' pass. That pass relied on the ability to snoop on AA queries at different points in the analysis group chain. Instead, I'm planning to build printing functionality directly into the aggregation layer. I've not included that in this patch merely to keep it smaller. Note that all of this needs a nearly complete rewrite of the AA documentation. I'm planning to do that, but I'd like to make sure the new design settles, and to flesh out a bit more of what it looks like in the new pass manager first. Differential Revision: http://reviews.llvm.org/D12080 llvm-svn: 247167
2015-09-10 01:55:00 +08:00
unwrap(PM)->add(createScopedNoAliasAAWrapperPass());
Add scoped-noalias metadata This commit adds scoped noalias metadata. The primary motivations for this feature are: 1. To preserve noalias function attribute information when inlining 2. To provide the ability to model block-scope C99 restrict pointers Neither of these two abilities are added here, only the necessary infrastructure. In fact, there should be no change to existing functionality, only the addition of new features. The logic that converts noalias function parameters into this metadata during inlining will come in a follow-up commit. What is added here is the ability to generally specify noalias memory-access sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA nodes: !scope0 = metadata !{ metadata !"scope of foo()" } !scope1 = metadata !{ metadata !"scope 1", metadata !scope0 } !scope2 = metadata !{ metadata !"scope 2", metadata !scope0 } !scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 } !scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 } Loads and stores can be tagged with an alias-analysis scope, and also, with a noalias tag for a specific scope: ... = load %ptr1, !alias.scope !{ !scope1 } ... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 } When evaluating an aliasing query, if one of the instructions is associated with an alias.scope id that is identical to the noalias scope associated with the other instruction, or is a descendant (in the scope hierarchy) of the noalias scope associated with the other instruction, then the two memory accesses are assumed not to alias. Note that is the first element of the scope metadata is a string, then it can be combined accross functions and translation units. The string can be replaced by a self-reference to create globally unqiue scope identifiers. [Note: This overview is slightly stylized, since the metadata nodes really need to just be numbers (!0 instead of !scope0), and the scope lists are also global unnamed metadata.] Existing noalias metadata in a callee is "cloned" for use by the inlined code. This is necessary because the aliasing scopes are unique to each call site (because of possible control dependencies on the aliasing properties). For example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } -- now just because we know that a1 does not alias with b1 at the first call site, and a2 does not alias with b2 at the second call site, we cannot let inlining these functons have the metadata imply that a1 does not alias with b2. llvm-svn: 213864
2014-07-24 22:25:39 +08:00
}
void LLVMAddBasicAliasAnalysisPass(LLVMPassManagerRef PM) {
[PM/AA] Rebuild LLVM's alias analysis infrastructure in a way compatible with the new pass manager, and no longer relying on analysis groups. This builds essentially a ground-up new AA infrastructure stack for LLVM. The core ideas are the same that are used throughout the new pass manager: type erased polymorphism and direct composition. The design is as follows: - FunctionAAResults is a type-erasing alias analysis results aggregation interface to walk a single query across a range of results from different alias analyses. Currently this is function-specific as we always assume that aliasing queries are *within* a function. - AAResultBase is a CRTP utility providing stub implementations of various parts of the alias analysis result concept, notably in several cases in terms of other more general parts of the interface. This can be used to implement only a narrow part of the interface rather than the entire interface. This isn't really ideal, this logic should be hoisted into FunctionAAResults as currently it will cause a significant amount of redundant work, but it faithfully models the behavior of the prior infrastructure. - All the alias analysis passes are ported to be wrapper passes for the legacy PM and new-style analysis passes for the new PM with a shared result object. In some cases (most notably CFL), this is an extremely naive approach that we should revisit when we can specialize for the new pass manager. - BasicAA has been restructured to reflect that it is much more fundamentally a function analysis because it uses dominator trees and loop info that need to be constructed for each function. All of the references to getting alias analysis results have been updated to use the new aggregation interface. All the preservation and other pass management code has been updated accordingly. The way the FunctionAAResultsWrapperPass works is to detect the available alias analyses when run, and add them to the results object. This means that we should be able to continue to respect when various passes are added to the pipeline, for example adding CFL or adding TBAA passes should just cause their results to be available and to get folded into this. The exception to this rule is BasicAA which really needs to be a function pass due to using dominator trees and loop info. As a consequence, the FunctionAAResultsWrapperPass directly depends on BasicAA and always includes it in the aggregation. This has significant implications for preserving analyses. Generally, most passes shouldn't bother preserving FunctionAAResultsWrapperPass because rebuilding the results just updates the set of known AA passes. The exception to this rule are LoopPass instances which need to preserve all the function analyses that the loop pass manager will end up needing. This means preserving both BasicAAWrapperPass and the aggregating FunctionAAResultsWrapperPass. Now, when preserving an alias analysis, you do so by directly preserving that analysis. This is only necessary for non-immutable-pass-provided alias analyses though, and there are only three of interest: BasicAA, GlobalsAA (formerly GlobalsModRef), and SCEVAA. Usually BasicAA is preserved when needed because it (like DominatorTree and LoopInfo) is marked as a CFG-only pass. I've expanded GlobalsAA into the preserved set everywhere we previously were preserving all of AliasAnalysis, and I've added SCEVAA in the intersection of that with where we preserve SCEV itself. One significant challenge to all of this is that the CGSCC passes were actually using the alias analysis implementations by taking advantage of a pretty amazing set of loop holes in the old pass manager's analysis management code which allowed analysis groups to slide through in many cases. Moving away from analysis groups makes this problem much more obvious. To fix it, I've leveraged the flexibility the design of the new PM components provides to just directly construct the relevant alias analyses for the relevant functions in the IPO passes that need them. This is a bit hacky, but should go away with the new pass manager, and is already in many ways cleaner than the prior state. Another significant challenge is that various facilities of the old alias analysis infrastructure just don't fit any more. The most significant of these is the alias analysis 'counter' pass. That pass relied on the ability to snoop on AA queries at different points in the analysis group chain. Instead, I'm planning to build printing functionality directly into the aggregation layer. I've not included that in this patch merely to keep it smaller. Note that all of this needs a nearly complete rewrite of the AA documentation. I'm planning to do that, but I'd like to make sure the new design settles, and to flesh out a bit more of what it looks like in the new pass manager first. Differential Revision: http://reviews.llvm.org/D12080 llvm-svn: 247167
2015-09-10 01:55:00 +08:00
unwrap(PM)->add(createBasicAAWrapperPass());
}
void LLVMAddLowerExpectIntrinsicPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLowerExpectIntrinsicPass());
}