diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp index 295cd52f1e6..83fb188f26b 100644 --- a/lib/Transforms/Vectorize/SLPVectorizer.cpp +++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp @@ -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/DemandedBits.h" +#include "llvm/Analysis/GlobalsModRef.h" +#include "llvm/Analysis/LoopAccessAnalysis.h" #include "llvm/Analysis/LoopInfo.h" #include "llvm/Analysis/LoopAccessAnalysis.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 #include #include @@ -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 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; @@ -1799,9 +1818,19 @@ 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); } Cost += getSpillCost(); @@ -2499,7 +2528,21 @@ 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(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"); @@ -2532,6 +2575,8 @@ 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); } @@ -2539,12 +2584,16 @@ Value *BoUpSLP::vectorizeTree() { } else { Builder.SetInsertPoint(cast(User)); Value *Ex = Builder.CreateExtractElement(Vec, Lane); + if (MinBWs.count(ScalarRoot)) + Ex = Builder.CreateSExt(Ex, Scalar->getType()); CSEBlocks.insert(cast(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); } @@ -3113,7 +3162,7 @@ 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(I)) - MaxWidth = std::max(MaxWidth, (unsigned)DL.getTypeSizeInBits(Ty)); + MaxWidth = std::max(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 @@ -3140,6 +3189,166 @@ 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 &Expr, + SmallVectorImpl &ToDemote, + SmallVectorImpl &Roots) { + + // We can always demote constants. + if (isa(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(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(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(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(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 Expr(TreeRoot.begin(), TreeRoot.end()); + for (auto &EU : ExternalUses) + if (!Expr.erase(EU.Scalar)) + return; + if (!Expr.empty()) + return; + + // Collect the scalar values in one lane 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[0]); + + // Conservatively determine if we can actually truncate the root of the + // expression. Collect the values that can be demoted in ToDemote and + // additional roots that require investigating in Roots. + SmallVector ToDemote; + SmallVector Roots; + if (!collectValuesToDemote(TreeRoot[0], 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 root + // of the expression to this width. + auto MaxBitWidth = 8u; + + // We first check if all the bits of the root are demanded. If they're not, + // we can truncate the root to this narrower type. + auto Mask = DB->getDemandedBits(cast(TreeRoot[0])); + if (Mask.countLeadingZeros() > 0) + MaxBitWidth = std::max( + Mask.getBitWidth() - Mask.countLeadingZeros(), MaxBitWidth); + + // If all the bits of the root 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. + else + for (auto *Scalar : ToDemote) { + auto NumSignBits = ComputeNumSignBits(Scalar, DL, 0, AC, 0, DT); + auto NumTypeBits = DL.getTypeSizeInBits(Scalar->getType()); + MaxBitWidth = std::max(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 StoreList; @@ -3161,6 +3370,7 @@ struct SLPVectorizer : public FunctionPass { LoopInfo *LI; DominatorTree *DT; AssumptionCache *AC; + DemandedBits *DB; bool runOnFunction(Function &F) override { if (skipOptnoneFunction(F)) @@ -3174,6 +3384,7 @@ struct SLPVectorizer : public FunctionPass { LI = &getAnalysis().getLoopInfo(); DT = &getAnalysis().getDomTree(); AC = &getAnalysis().getAssumptionCache(F); + DB = &getAnalysis(); Stores.clear(); GEPs.clear(); @@ -3203,7 +3414,7 @@ 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. @@ -3246,6 +3457,7 @@ struct SLPVectorizer : public FunctionPass { AU.addRequired(); AU.addRequired(); AU.addRequired(); + AU.addRequired(); AU.addPreserved(); AU.addPreserved(); AU.addPreserved(); @@ -3350,6 +3562,7 @@ bool SLPVectorizer::vectorizeStoreChain(ArrayRef Chain, ArrayRef Operands = Chain.slice(i, VF); R.buildTree(Operands); + R.computeMinimumValueSizes(); int Cost = R.getTreeCost(); @@ -3549,6 +3762,7 @@ bool SLPVectorizer::tryToVectorizeList(ArrayRef VL, BoUpSLP &R, Value *ReorderedOps[] = { Ops[1], Ops[0] }; R.buildTree(ReorderedOps, None); } + R.computeMinimumValueSizes(); int Cost = R.getTreeCost(); if (Cost < -SLPCostThreshold) { @@ -3815,6 +4029,7 @@ 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]); diff --git a/test/Transforms/SLPVectorizer/AArch64/gather-reduce.ll b/test/Transforms/SLPVectorizer/AArch64/gather-reduce.ll index 59ceba1717a..9c06b24163a 100644 --- a/test/Transforms/SLPVectorizer/AArch64/gather-reduce.ll +++ b/test/Transforms/SLPVectorizer/AArch64/gather-reduce.ll @@ -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: