From e97b102e2b597751c9e9edce74d3d69bba317dcd Mon Sep 17 00:00:00 2001 From: Nick Lewycky Date: Thu, 30 May 2013 04:33:38 +0000 Subject: Swizzle vector inputs if it helps us eliminate shuffles. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182909 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/InstCombine/InstCombine.h | 1 + .../InstCombine/InstCombineVectorOps.cpp | 245 +++++++++++++++++++++ test/Transforms/InstCombine/vec_shuffle.ll | 12 + 3 files changed, 258 insertions(+) diff --git a/lib/Transforms/InstCombine/InstCombine.h b/lib/Transforms/InstCombine/InstCombine.h index b1eefd214d..b3084ccd2c 100644 --- a/lib/Transforms/InstCombine/InstCombine.h +++ b/lib/Transforms/InstCombine/InstCombine.h @@ -234,6 +234,7 @@ private: bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS); Value *EmitGEPOffset(User *GEP); Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN); + Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef Mask); public: // InsertNewInstBefore - insert an instruction New before instruction Old diff --git a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp index d4344c3c4d..ffab87faf6 100644 --- a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp +++ b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp @@ -494,6 +494,241 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) { return 0; } +/// Return true if we can evaluate the specified expression tree if the vector +/// elements were shuffled in a different order. +static bool CanEvaluateShuffled(Value *V, ArrayRef Mask, + unsigned Depth = 100) { + // We can always reorder the elements of a constant. + if (isa(V)) + return true; + + // We won't reorder vector arguments. No IPO here. + Instruction *I = dyn_cast(V); + if (!I) return false; + + // Two users may expect different orders of the elements. Don't try it. + if (!I->hasOneUse()) + return false; + + if (Depth == 0) return false; + + switch (I->getOpcode()) { + case Instruction::Add: + case Instruction::FAdd: + case Instruction::Sub: + case Instruction::FSub: + case Instruction::Mul: + case Instruction::FMul: + case Instruction::UDiv: + case Instruction::SDiv: + case Instruction::FDiv: + case Instruction::URem: + case Instruction::SRem: + case Instruction::FRem: + case Instruction::Shl: + case Instruction::LShr: + case Instruction::AShr: + case Instruction::And: + case Instruction::Or: + case Instruction::Xor: + case Instruction::ICmp: + case Instruction::FCmp: + case Instruction::Trunc: + case Instruction::ZExt: + case Instruction::SExt: + case Instruction::FPToUI: + case Instruction::FPToSI: + case Instruction::UIToFP: + case Instruction::SIToFP: + case Instruction::FPTrunc: + case Instruction::FPExt: + case Instruction::GetElementPtr: { + for (int i = 0, e = I->getNumOperands(); i != e; ++i) { + if (!CanEvaluateShuffled(I->getOperand(i), Mask, Depth-1)) + return false; + } + return true; + } + case Instruction::InsertElement: { + ConstantInt *CI = dyn_cast(I->getOperand(2)); + if (!CI) return false; + int ElementNumber = CI->getLimitedValue(); + + // Verify that 'CI' does not occur twice in Mask. A single 'insertelement' + // can't put an element into multiple indices. + bool SeenOnce = false; + for (int i = 0, e = Mask.size(); i != e; ++i) { + if (Mask[i] == ElementNumber) { + if (SeenOnce) + return false; + SeenOnce = true; + } + } + return CanEvaluateShuffled(I->getOperand(0), Mask, Depth-1); + } + } + return false; +} + +/// Rebuild a new instruction just like 'I' but with the new operands given. +/// In the event of type mismatch, the type of the operands is correct. +static Value *BuildNew(Instruction *I, ArrayRef NewOps) { + // We don't want to use the IRBuilder here because we want the replacement + // instructions to appear next to 'I', not the builder's insertion point. + switch (I->getOpcode()) { + case Instruction::Add: + case Instruction::FAdd: + case Instruction::Sub: + case Instruction::FSub: + case Instruction::Mul: + case Instruction::FMul: + case Instruction::UDiv: + case Instruction::SDiv: + case Instruction::FDiv: + case Instruction::URem: + case Instruction::SRem: + case Instruction::FRem: + case Instruction::Shl: + case Instruction::LShr: + case Instruction::AShr: + case Instruction::And: + case Instruction::Or: + case Instruction::Xor: { + BinaryOperator *BO = cast(I); + assert(NewOps.size() == 2 && "binary operator with #ops != 2"); + BinaryOperator *New = + BinaryOperator::Create(cast(I)->getOpcode(), + NewOps[0], NewOps[1], "", BO); + if (isa(BO)) { + New->setHasNoUnsignedWrap(BO->hasNoUnsignedWrap()); + New->setHasNoSignedWrap(BO->hasNoSignedWrap()); + } + if (isa(BO)) { + New->setIsExact(BO->isExact()); + } + return New; + } + case Instruction::ICmp: + assert(NewOps.size() == 2 && "icmp with #ops != 2"); + return new ICmpInst(I, cast(I)->getPredicate(), + NewOps[0], NewOps[1]); + case Instruction::FCmp: + assert(NewOps.size() == 2 && "fcmp with #ops != 2"); + return new FCmpInst(I, cast(I)->getPredicate(), + NewOps[0], NewOps[1]); + case Instruction::Trunc: + case Instruction::ZExt: + case Instruction::SExt: + case Instruction::FPToUI: + case Instruction::FPToSI: + case Instruction::UIToFP: + case Instruction::SIToFP: + case Instruction::FPTrunc: + case Instruction::FPExt: { + // It's possible that the mask has a different number of elements from + // the original cast. We recompute the destination type to match the mask. + Type *DestTy = + VectorType::get(I->getType()->getScalarType(), + NewOps[0]->getType()->getVectorNumElements()); + assert(NewOps.size() == 1 && "cast with #ops != 1"); + return CastInst::Create(cast(I)->getOpcode(), NewOps[0], DestTy, + "", I); + } + case Instruction::GetElementPtr: { + Value *Ptr = NewOps[0]; + ArrayRef Idx = NewOps.slice(1); + GetElementPtrInst *GEP = GetElementPtrInst::Create(Ptr, Idx, "", I); + GEP->setIsInBounds(cast(I)->isInBounds()); + return GEP; + } + } + llvm_unreachable("failed to rebuild vector instructions"); +} + +Value * +InstCombiner::EvaluateInDifferentElementOrder(Value *V, ArrayRef Mask) { + // Mask.size() does not need to be equal to the number of vector elements. + + assert(V->getType()->isVectorTy() && "can't reorder non-vector elements"); + if (isa(V)) { + return UndefValue::get(VectorType::get(V->getType()->getScalarType(), + Mask.size())); + } + if (isa(V)) { + return ConstantAggregateZero::get( + VectorType::get(V->getType()->getScalarType(), + Mask.size())); + } + if (Constant *C = dyn_cast(V)) { + SmallVector MaskValues; + for (int i = 0, e = Mask.size(); i != e; ++i) { + if (Mask[i] == -1) + MaskValues.push_back(UndefValue::get(Builder->getInt32Ty())); + else + MaskValues.push_back(Builder->getInt32(Mask[i])); + } + return ConstantExpr::getShuffleVector(C, UndefValue::get(C->getType()), + ConstantVector::get(MaskValues)); + } + + Instruction *I = cast(V); + switch (I->getOpcode()) { + case Instruction::Add: + case Instruction::FAdd: + case Instruction::Sub: + case Instruction::FSub: + case Instruction::Mul: + case Instruction::FMul: + case Instruction::UDiv: + case Instruction::SDiv: + case Instruction::FDiv: + case Instruction::URem: + case Instruction::SRem: + case Instruction::FRem: + case Instruction::Shl: + case Instruction::LShr: + case Instruction::AShr: + case Instruction::And: + case Instruction::Or: + case Instruction::Xor: + case Instruction::ICmp: + case Instruction::FCmp: + case Instruction::Trunc: + case Instruction::ZExt: + case Instruction::SExt: + case Instruction::FPToUI: + case Instruction::FPToSI: + case Instruction::UIToFP: + case Instruction::SIToFP: + case Instruction::FPTrunc: + case Instruction::FPExt: + case Instruction::Select: + case Instruction::GetElementPtr: { + SmallVector NewOps; + bool NeedsRebuild = (Mask.size() != I->getType()->getVectorNumElements()); + for (int i = 0, e = I->getNumOperands(); i != e; ++i) { + Value *V = EvaluateInDifferentElementOrder(I->getOperand(i), Mask); + NewOps.push_back(V); + NeedsRebuild |= (V != I->getOperand(i)); + } + if (NeedsRebuild) { + return BuildNew(I, NewOps); + } + return I; + } + case Instruction::InsertElement: { + uint32_t Element = cast(I->getOperand(2))->getLimitedValue(); + if (Element >= Mask.size()) { + // Such instructions are valid and exhibit undefined behaviour. + return UndefValue::get(I->getType()); + } + Value *V = EvaluateInDifferentElementOrder(I->getOperand(0), Mask); + return InsertElementInst::Create(V, I->getOperand(1), + Builder->getInt32(Mask[Element]), "", I); + } + } + llvm_unreachable("failed to reorder elements of vector instruction!"); +} Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { Value *LHS = SVI.getOperand(0); @@ -574,6 +809,16 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { if (isRHSID) return ReplaceInstUsesWith(SVI, RHS); } + if (isa(RHS) && + // This isn't necessary for correctness, but the comment block below + // claims that there are cases where folding two shuffles into one would + // cause worse codegen on some targets. + !isa(LHS) && + CanEvaluateShuffled(LHS, Mask)) { + Value *V = EvaluateInDifferentElementOrder(LHS, Mask); + return ReplaceInstUsesWith(SVI, V); + } + // If the LHS is a shufflevector itself, see if we can combine it with this // one without producing an unusual shuffle. // Cases that might be simplified: diff --git a/test/Transforms/InstCombine/vec_shuffle.ll b/test/Transforms/InstCombine/vec_shuffle.ll index 8f78c2e6bd..9dc29e4c6c 100644 --- a/test/Transforms/InstCombine/vec_shuffle.ll +++ b/test/Transforms/InstCombine/vec_shuffle.ll @@ -153,3 +153,15 @@ define <8 x i8> @test12a(<8 x i8> %tmp6, <8 x i8> %tmp2) nounwind { ret <8 x i8> %tmp3 } +define <2 x i8> @test13(i8 %x1, i8 %x2) { +; CHECK: @test13 +; CHECK-NEXT: insertelement {{.*}} undef, i8 %x1, i32 1 +; CHECK-NEXT: insertelement {{.*}} i8 %x2, i32 0 +; CHECK-NEXT: add {{.*}} +; CHECK-NEXT: ret + %A = insertelement <2 x i8> undef, i8 %x1, i32 0 + %B = insertelement <2 x i8> %A, i8 %x2, i32 1 + %C = add <2 x i8> %B, + %D = shufflevector <2 x i8> %C, <2 x i8> undef, <2 x i32> + ret <2 x i8> %D +} -- cgit v1.2.3