maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Reapply commit r259357 with a fix for PR26629 

Commit r259357 was reverted because it caused PR26629. We were assuming all
roots of a vectorizable tree could be truncated to the same width, which is not
the case in general. This commit reapplies the patch along with a fix and a new
test case to ensure we don't regress because of this issue again. This should
fix PR26629.

llvm-svn: 261212
This commit is contained in:
Matthew Simpson 2016-02-18 14:14:40 +00:00
parent f034021443
commit 92821cb4a8
3 changed files with 284 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

249
llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
View File

@ -15,22 +15,24 @@
// "Loop-Aware SLP in GCC" by Ira Rosen, Dorit Nuzman, Ayal Zaks.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Vectorize.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/DemandedBits.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/LoopAccessAnalysis.h"
#include "llvm/Analysis/LoopAccessAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
@ -45,7 +47,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/Transforms/Vectorize.h"
#include <algorithm>
#include <map>
#include <memory>
@ -364,9 +366,9 @@ public:
BoUpSLP(Function *Func, ScalarEvolution *Se, TargetTransformInfo *Tti,
TargetLibraryInfo *TLi, AliasAnalysis *Aa, LoopInfo *Li,
DominatorTree *Dt, AssumptionCache *AC)
DominatorTree *Dt, AssumptionCache *AC, DemandedBits *DB)
: NumLoadsWantToKeepOrder(0), NumLoadsWantToChangeOrder(0), F(Func),
SE(Se), TTI(Tti), TLI(TLi), AA(Aa), LI(Li), DT(Dt),
SE(Se), TTI(Tti), TLI(TLi), AA(Aa), LI(Li), DT(Dt), AC(AC), DB(DB),
Builder(Se->getContext()) {
CodeMetrics::collectEphemeralValues(F, AC, EphValues);
}
@ -400,6 +402,7 @@ public:
BlockScheduling *BS = Iter.second.get();
BS->clear();
}
MinBWs.clear();
}
/// \brief Perform LICM and CSE on the newly generated gather sequences.
@ -417,6 +420,10 @@ public:
/// vectorization factors.
unsigned getVectorElementSize(Value *V);
/// Compute the minimum type sizes required to represent the entries in a
/// vectorizable tree.
void computeMinimumValueSizes();
private:
struct TreeEntry;
@ -914,8 +921,14 @@ private:
AliasAnalysis *AA;
LoopInfo *LI;
DominatorTree *DT;
AssumptionCache *AC;
DemandedBits *DB;
/// Instruction builder to construct the vectorized tree.
IRBuilder<> Builder;
/// A map of scalar integer values to the smallest bit width with which they
/// can legally be represented.
MapVector<Value *, uint64_t> MinBWs;
};
#ifndef NDEBUG
@ -1471,6 +1484,12 @@ int BoUpSLP::getEntryCost(TreeEntry *E) {
ScalarTy = SI->getValueOperand()->getType();
VectorType *VecTy = VectorType::get(ScalarTy, VL.size());
// If we have computed a smaller type for the expression, update VecTy so
// that the costs will be accurate.
if (MinBWs.count(VL[0]))
VecTy = VectorType::get(IntegerType::get(F->getContext(), MinBWs[VL[0]]),
VL.size());
if (E->NeedToGather) {
if (allConstant(VL))
return 0;
@ -1798,9 +1817,19 @@ int BoUpSLP::getTreeCost() {
if (EphValues.count(EU.User))
continue;
VectorType *VecTy = VectorType::get(EU.Scalar->getType(), BundleWidth);
ExtractCost += TTI->getVectorInstrCost(Instruction::ExtractElement, VecTy,
EU.Lane);
// If we plan to rewrite the tree in a smaller type, we will need to sign
// extend the extracted value back to the original type. Here, we account
// for the extract and the added cost of the sign extend if needed.
auto *VecTy = VectorType::get(EU.Scalar->getType(), BundleWidth);
auto *ScalarRoot = VectorizableTree[0].Scalars[0];
if (MinBWs.count(ScalarRoot)) {
auto *MinTy = IntegerType::get(F->getContext(), MinBWs[ScalarRoot]);
VecTy = VectorType::get(MinTy, BundleWidth);
ExtractCost +=
TTI->getCastInstrCost(Instruction::SExt, EU.Scalar->getType(), MinTy);
}
ExtractCost +=
TTI->getVectorInstrCost(Instruction::ExtractElement, VecTy, EU.Lane);
}
int SpillCost = getSpillCost();
@ -2501,7 +2530,21 @@ Value *BoUpSLP::vectorizeTree() {
}
Builder.SetInsertPoint(&F->getEntryBlock().front());
vectorizeTree(&VectorizableTree[0]);
auto *VectorRoot = vectorizeTree(&VectorizableTree[0]);
// If the vectorized tree can be rewritten in a smaller type, we truncate the
// vectorized root. InstCombine will then rewrite the entire expression. We
// sign extend the extracted values below.
auto *ScalarRoot = VectorizableTree[0].Scalars[0];
if (MinBWs.count(ScalarRoot)) {
if (auto *I = dyn_cast<Instruction>(VectorRoot))
Builder.SetInsertPoint(&*++BasicBlock::iterator(I));
auto BundleWidth = VectorizableTree[0].Scalars.size();
auto *MinTy = IntegerType::get(F->getContext(), MinBWs[ScalarRoot]);
auto *VecTy = VectorType::get(MinTy, BundleWidth);
auto *Trunc = Builder.CreateTrunc(VectorRoot, VecTy);
VectorizableTree[0].VectorizedValue = Trunc;
}
DEBUG(dbgs() << "SLP: Extracting " << ExternalUses.size() << " values .\n");
@ -2534,6 +2577,8 @@ Value *BoUpSLP::vectorizeTree() {
if (PH->getIncomingValue(i) == Scalar) {
Builder.SetInsertPoint(PH->getIncomingBlock(i)->getTerminator());
Value *Ex = Builder.CreateExtractElement(Vec, Lane);
if (MinBWs.count(ScalarRoot))
Ex = Builder.CreateSExt(Ex, Scalar->getType());
CSEBlocks.insert(PH->getIncomingBlock(i));
PH->setOperand(i, Ex);
}
@ -2541,12 +2586,16 @@ Value *BoUpSLP::vectorizeTree() {
} else {
Builder.SetInsertPoint(cast<Instruction>(User));
Value *Ex = Builder.CreateExtractElement(Vec, Lane);
if (MinBWs.count(ScalarRoot))
Ex = Builder.CreateSExt(Ex, Scalar->getType());
CSEBlocks.insert(cast<Instruction>(User)->getParent());
User->replaceUsesOfWith(Scalar, Ex);
}
} else {
Builder.SetInsertPoint(&F->getEntryBlock().front());
Value *Ex = Builder.CreateExtractElement(Vec, Lane);
if (MinBWs.count(ScalarRoot))
Ex = Builder.CreateSExt(Ex, Scalar->getType());
CSEBlocks.insert(&F->getEntryBlock());
User->replaceUsesOfWith(Scalar, Ex);
}
@ -3115,7 +3164,7 @@ unsigned BoUpSLP::getVectorElementSize(Value *V) {
// If the current instruction is a load, update MaxWidth to reflect the
// width of the loaded value.
else if (isa<LoadInst>(I))
MaxWidth = std::max(MaxWidth, (unsigned)DL.getTypeSizeInBits(Ty));
MaxWidth = std::max<unsigned>(MaxWidth, DL.getTypeSizeInBits(Ty));
// Otherwise, we need to visit the operands of the instruction. We only
// handle the interesting cases from buildTree here. If an operand is an
@ -3142,6 +3191,176 @@ unsigned BoUpSLP::getVectorElementSize(Value *V) {
return MaxWidth;
}
// Determine if a value V in a vectorizable expression Expr can be demoted to a
// smaller type with a truncation. We collect the values that will be demoted
// in ToDemote and additional roots that require investigating in Roots.
static bool collectValuesToDemote(Value *V, SmallPtrSetImpl<Value *> &Expr,
SmallVectorImpl<Value *> &ToDemote,
SmallVectorImpl<Value *> &Roots) {
// We can always demote constants.
if (isa<Constant>(V)) {
ToDemote.push_back(V);
return true;
}
// If the value is not an instruction in the expression with only one use, it
// cannot be demoted.
auto *I = dyn_cast<Instruction>(V);
if (!I || !I->hasOneUse() || !Expr.count(I))
return false;
switch (I->getOpcode()) {
// We can always demote truncations and extensions. Since truncations can
// seed additional demotion, we save the truncated value.
case Instruction::Trunc:
Roots.push_back(I->getOperand(0));
case Instruction::ZExt:
case Instruction::SExt:
break;
// We can demote certain binary operations if we can demote both of their
// operands.
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
if (!collectValuesToDemote(I->getOperand(0), Expr, ToDemote, Roots) ||
!collectValuesToDemote(I->getOperand(1), Expr, ToDemote, Roots))
return false;
break;
// We can demote selects if we can demote their true and false values.
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
if (!collectValuesToDemote(SI->getTrueValue(), Expr, ToDemote, Roots) ||
!collectValuesToDemote(SI->getFalseValue(), Expr, ToDemote, Roots))
return false;
break;
}
// We can demote phis if we can demote all their incoming operands. Note that
// we don't need to worry about cycles since we ensure single use above.
case Instruction::PHI: {
PHINode *PN = cast<PHINode>(I);
for (Value *IncValue : PN->incoming_values())
if (!collectValuesToDemote(IncValue, Expr, ToDemote, Roots))
return false;
break;
}
// Otherwise, conservatively give up.
default:
return false;
}
// Record the value that we can demote.
ToDemote.push_back(V);
return true;
}
void BoUpSLP::computeMinimumValueSizes() {
auto &DL = F->getParent()->getDataLayout();
// If there are no external uses, the expression tree must be rooted by a
// store. We can't demote in-memory values, so there is nothing to do here.
if (ExternalUses.empty())
return;
// We only attempt to truncate integer expressions.
auto &TreeRoot = VectorizableTree[0].Scalars;
auto *TreeRootIT = dyn_cast<IntegerType>(TreeRoot[0]->getType());
if (!TreeRootIT)
return;
// If the expression is not rooted by a store, these roots should have
// external uses. We will rely on InstCombine to rewrite the expression in
// the narrower type. However, InstCombine only rewrites single-use values.
// This means that if a tree entry other than a root is used externally, it
// must have multiple uses and InstCombine will not rewrite it. The code
// below ensures that only the roots are used externally.
SmallPtrSet<Value *, 32> Expr(TreeRoot.begin(), TreeRoot.end());
for (auto &EU : ExternalUses)
if (!Expr.erase(EU.Scalar))
return;
if (!Expr.empty())
return;
// Collect the scalar values of the vectorizable expression. We will use this
// context to determine which values can be demoted. If we see a truncation,
// we mark it as seeding another demotion.
for (auto &Entry : VectorizableTree)
Expr.insert(Entry.Scalars.begin(), Entry.Scalars.end());
// Ensure the roots of the vectorizable tree don't form a cycle. They must
// have a single external user that is not in the vectorizable tree.
for (auto *Root : TreeRoot)
if (!Root->hasOneUse() || Expr.count(*Root->user_begin()))
return;
// Conservatively determine if we can actually truncate the roots of the
// expression. Collect the values that can be demoted in ToDemote and
// additional roots that require investigating in Roots.
SmallVector<Value *, 32> ToDemote;
SmallVector<Value *, 4> Roots;
for (auto *Root : TreeRoot)
if (!collectValuesToDemote(Root, Expr, ToDemote, Roots))
return;
// The maximum bit width required to represent all the values that can be
// demoted without loss of precision. It would be safe to truncate the roots
// of the expression to this width.
auto MaxBitWidth = 8u;
// We first check if all the bits of the roots are demanded. If they're not,
// we can truncate the roots to this narrower type.
for (auto *Root : TreeRoot) {
auto Mask = DB->getDemandedBits(cast<Instruction>(Root));
MaxBitWidth = std::max<unsigned>(
Mask.getBitWidth() - Mask.countLeadingZeros(), MaxBitWidth);
}
// If all the bits of the roots are demanded, we can try a little harder to
// compute a narrower type. This can happen, for example, if the roots are
// getelementptr indices. InstCombine promotes these indices to the pointer
// width. Thus, all their bits are technically demanded even though the
// address computation might be vectorized in a smaller type.
//
// We start by looking at each entry that can be demoted. We compute the
// maximum bit width required to store the scalar by using ValueTracking to
// compute the number of high-order bits we can truncate.
if (MaxBitWidth == DL.getTypeSizeInBits(TreeRoot[0]->getType())) {
MaxBitWidth = 8u;
for (auto *Scalar : ToDemote) {
auto NumSignBits = ComputeNumSignBits(Scalar, DL, 0, AC, 0, DT);
auto NumTypeBits = DL.getTypeSizeInBits(Scalar->getType());
MaxBitWidth = std::max<unsigned>(NumTypeBits - NumSignBits, MaxBitWidth);
}
}
// Round MaxBitWidth up to the next power-of-two.
if (!isPowerOf2_64(MaxBitWidth))
MaxBitWidth = NextPowerOf2(MaxBitWidth);
// If the maximum bit width we compute is less than the with of the roots'
// type, we can proceed with the narrowing. Otherwise, do nothing.
if (MaxBitWidth >= TreeRootIT->getBitWidth())
return;
// If we can truncate the root, we must collect additional values that might
// be demoted as a result. That is, those seeded by truncations we will
// modify.
while (!Roots.empty())
collectValuesToDemote(Roots.pop_back_val(), Expr, ToDemote, Roots);
// Finally, map the values we can demote to the maximum bit with we computed.
for (auto *Scalar : ToDemote)
MinBWs[Scalar] = MaxBitWidth;
}
/// The SLPVectorizer Pass.
struct SLPVectorizer : public FunctionPass {
typedef SmallVector<StoreInst *, 8> StoreList;
@ -3163,6 +3382,7 @@ struct SLPVectorizer : public FunctionPass {
LoopInfo *LI;
DominatorTree *DT;
AssumptionCache *AC;
DemandedBits *DB;
bool runOnFunction(Function &F) override {
if (skipOptnoneFunction(F))
@ -3176,6 +3396,7 @@ struct SLPVectorizer : public FunctionPass {
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
DB = &getAnalysis<DemandedBits>();
Stores.clear();
GEPs.clear();
@ -3205,7 +3426,7 @@ struct SLPVectorizer : public FunctionPass {
// Use the bottom up slp vectorizer to construct chains that start with
// store instructions.
BoUpSLP R(&F, SE, TTI, TLI, AA, LI, DT, AC);
BoUpSLP R(&F, SE, TTI, TLI, AA, LI, DT, AC, DB);
// A general note: the vectorizer must use BoUpSLP::eraseInstruction() to
// delete instructions.
@ -3248,6 +3469,7 @@ struct SLPVectorizer : public FunctionPass {
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<DemandedBits>();
AU.addPreserved<LoopInfoWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addPreserved<AAResultsWrapperPass>();
@ -3352,6 +3574,7 @@ bool SLPVectorizer::vectorizeStoreChain(ArrayRef<Value *> Chain,
ArrayRef<Value *> Operands = Chain.slice(i, VF);
R.buildTree(Operands);
R.computeMinimumValueSizes();
int Cost = R.getTreeCost();
@ -3551,6 +3774,7 @@ bool SLPVectorizer::tryToVectorizeList(ArrayRef<Value *> VL, BoUpSLP &R,
Value *ReorderedOps[] = { Ops[1], Ops[0] };
R.buildTree(ReorderedOps, None);
}
R.computeMinimumValueSizes();
int Cost = R.getTreeCost();
if (Cost < -SLPCostThreshold) {
@ -3817,6 +4041,7 @@ public:
for (; i < NumReducedVals - ReduxWidth + 1; i += ReduxWidth) {
V.buildTree(makeArrayRef(&ReducedVals[i], ReduxWidth), ReductionOps);
V.computeMinimumValueSizes();
// Estimate cost.
int Cost = V.getTreeCost() + getReductionCost(TTI, ReducedVals[i]);

31
llvm/test/Transforms/SLPVectorizer/AArch64/gather-reduce.ll
View File

@ -1,4 +1,5 @@
; RUN: opt -S -slp-vectorizer -dce -instcombine < %s | FileCheck %s
; RUN: opt -S -slp-vectorizer -dce -instcombine < %s | FileCheck %s --check-prefix=PROFITABLE
; RUN: opt -S -slp-vectorizer -slp-threshold=-12 -dce -instcombine < %s | FileCheck %s --check-prefix=UNPROFITABLE
target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
target triple = "aarch64--linux-gnu"
@ -18,13 +19,13 @@ target triple = "aarch64--linux-gnu"
; return sum;
; }
; CHECK-LABEL: @gather_reduce_8x16_i32
; PROFITABLE-LABEL: @gather_reduce_8x16_i32
;
; CHECK: [[L:%[a-zA-Z0-9.]+]] = load <8 x i16>
; CHECK: zext <8 x i16> [[L]] to <8 x i32>
; CHECK: [[S:%[a-zA-Z0-9.]+]] = sub nsw <8 x i32>
; CHECK: [[X:%[a-zA-Z0-9.]+]] = extractelement <8 x i32> [[S]]
; CHECK: sext i32 [[X]] to i64
; PROFITABLE: [[L:%[a-zA-Z0-9.]+]] = load <8 x i16>
; PROFITABLE: zext <8 x i16> [[L]] to <8 x i32>
; PROFITABLE: [[S:%[a-zA-Z0-9.]+]] = sub nsw <8 x i32>
; PROFITABLE: [[X:%[a-zA-Z0-9.]+]] = extractelement <8 x i32> [[S]]
; PROFITABLE: sext i32 [[X]] to i64
;
define i32 @gather_reduce_8x16_i32(i16* nocapture readonly %a, i16* nocapture readonly %b, i16* nocapture readonly %g, i32 %n) {
entry:
@ -137,14 +138,18 @@ for.body:
br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body
}
; CHECK-LABEL: @gather_reduce_8x16_i64
; UNPROFITABLE-LABEL: @gather_reduce_8x16_i64
;
; CHECK-NOT: load <8 x i16>
; UNPROFITABLE: [[L:%[a-zA-Z0-9.]+]] = load <8 x i16>
; UNPROFITABLE: zext <8 x i16> [[L]] to <8 x i32>
; UNPROFITABLE: [[S:%[a-zA-Z0-9.]+]] = sub nsw <8 x i32>
; UNPROFITABLE: [[X:%[a-zA-Z0-9.]+]] = extractelement <8 x i32> [[S]]
; UNPROFITABLE: sext i32 [[X]] to i64
;
; FIXME: We are currently unable to vectorize the case with i64 subtraction
; because the zero extensions are too expensive. The solution here is to
; convert the i64 subtractions to i32 subtractions during vectorization.
; This would then match the case above.
; TODO: Although we can now vectorize this case while converting the i64
; subtractions to i32, the cost model currently finds vectorization to be
; unprofitable. The cost model is penalizing the sign and zero
; extensions in the vectorized version, but they are actually free.
;
define i32 @gather_reduce_8x16_i64(i16* nocapture readonly %a, i16* nocapture readonly %b, i16* nocapture readonly %g, i32 %n) {
entry:

29
llvm/test/Transforms/SLPVectorizer/AArch64/minimum-sizes.ll
View File

@ -24,3 +24,32 @@ for.cond4:
for.end11:
ret void
}
; This test ensures that we do not regress due to PR26629. We must look at
; every root in the vectorizable tree when computing minimum sizes since one
; root may require fewer bits than another.
;
; CHECK-LABEL: @PR26629
; CHECK-NOT: {{.*}} and <2 x i72>
;
define void @PR26629(i32* %c) {
entry:
br i1 undef, label %for.ph, label %for.end
for.ph:
%0 = load i32, i32* %c, align 4
br label %for.body
for.body:
%d = phi i72 [ 576507472957710340, %for.ph ], [ %bf.set17, %for.body ]
%sub = sub i32 %0, undef
%bf.clear13 = and i72 %d, -576460748008464384
%1 = zext i32 %sub to i72
%bf.value15 = and i72 %1, 8191
%bf.clear16 = or i72 %bf.value15, %bf.clear13
%bf.set17 = or i72 %bf.clear16, undef
br label %for.body
for.end:
ret void
}