[llvm] r182909 - Swizzle vector inputs if it helps us eliminate shuffles.
Nick Lewycky
nicholas at mxc.ca
Wed May 29 21:33:39 PDT 2013
Author: nicholas
Date: Wed May 29 23:33:38 2013
New Revision: 182909
URL: http://llvm.org/viewvc/llvm-project?rev=182909&view=rev
Log:
Swizzle vector inputs if it helps us eliminate shuffles.
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombine.h
llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombine.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombine.h?rev=182909&r1=182908&r2=182909&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombine.h (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombine.h Wed May 29 23:33:38 2013
@@ -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<int> Mask);
public:
// InsertNewInstBefore - insert an instruction New before instruction Old
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp?rev=182909&r1=182908&r2=182909&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp Wed May 29 23:33:38 2013
@@ -494,6 +494,241 @@ Instruction *InstCombiner::visitInsertEl
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<int> Mask,
+ unsigned Depth = 100) {
+ // We can always reorder the elements of a constant.
+ if (isa<Constant>(V))
+ return true;
+
+ // We won't reorder vector arguments. No IPO here.
+ Instruction *I = dyn_cast<Instruction>(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<ConstantInt>(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<Value*> 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<BinaryOperator>(I);
+ assert(NewOps.size() == 2 && "binary operator with #ops != 2");
+ BinaryOperator *New =
+ BinaryOperator::Create(cast<BinaryOperator>(I)->getOpcode(),
+ NewOps[0], NewOps[1], "", BO);
+ if (isa<OverflowingBinaryOperator>(BO)) {
+ New->setHasNoUnsignedWrap(BO->hasNoUnsignedWrap());
+ New->setHasNoSignedWrap(BO->hasNoSignedWrap());
+ }
+ if (isa<PossiblyExactOperator>(BO)) {
+ New->setIsExact(BO->isExact());
+ }
+ return New;
+ }
+ case Instruction::ICmp:
+ assert(NewOps.size() == 2 && "icmp with #ops != 2");
+ return new ICmpInst(I, cast<ICmpInst>(I)->getPredicate(),
+ NewOps[0], NewOps[1]);
+ case Instruction::FCmp:
+ assert(NewOps.size() == 2 && "fcmp with #ops != 2");
+ return new FCmpInst(I, cast<FCmpInst>(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<CastInst>(I)->getOpcode(), NewOps[0], DestTy,
+ "", I);
+ }
+ case Instruction::GetElementPtr: {
+ Value *Ptr = NewOps[0];
+ ArrayRef<Value*> Idx = NewOps.slice(1);
+ GetElementPtrInst *GEP = GetElementPtrInst::Create(Ptr, Idx, "", I);
+ GEP->setIsInBounds(cast<GetElementPtrInst>(I)->isInBounds());
+ return GEP;
+ }
+ }
+ llvm_unreachable("failed to rebuild vector instructions");
+}
+
+Value *
+InstCombiner::EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> 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<UndefValue>(V)) {
+ return UndefValue::get(VectorType::get(V->getType()->getScalarType(),
+ Mask.size()));
+ }
+ if (isa<ConstantAggregateZero>(V)) {
+ return ConstantAggregateZero::get(
+ VectorType::get(V->getType()->getScalarType(),
+ Mask.size()));
+ }
+ if (Constant *C = dyn_cast<Constant>(V)) {
+ SmallVector<Constant *, 16> 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<Instruction>(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<Value*, 8> 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<ConstantInt>(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::visitShuffleV
if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
}
+ if (isa<UndefValue>(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<ShuffleVectorInst>(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:
Modified: llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll?rev=182909&r1=182908&r2=182909&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll Wed May 29 23:33:38 2013
@@ -153,3 +153,15 @@ define <8 x i8> @test12a(<8 x i8> %tmp6,
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 {{.*}} <i8 7, i8 5>
+; 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, <i8 5, i8 7>
+ %D = shufflevector <2 x i8> %C, <2 x i8> undef, <2 x i32> <i32 1, i32 0>
+ ret <2 x i8> %D
+}
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