From: Eli Friedman Date: Fri, 21 Oct 2011 19:06:29 +0000 (+0000) Subject: Extend instcombine's shufflevector simplification to handle more cases where the... X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d2822e7572e75287db66acb14b2d988a80faebdd;p=oota-llvm.git Extend instcombine's shufflevector simplification to handle more cases where the input and output vectors have different sizes. Patch by Xiaoyi Guo. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142671 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp index 154267c0346..6dcfa0ddd29 100644 --- a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp +++ b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp @@ -55,14 +55,14 @@ static bool CheapToScalarize(Value *V, bool isConstant) { /// getShuffleMask - Read and decode a shufflevector mask. /// Turn undef elements into negative values. -static std::vector getShuffleMask(const ShuffleVectorInst *SVI) { +static SmallVector getShuffleMask(const ShuffleVectorInst *SVI) { unsigned NElts = SVI->getType()->getNumElements(); if (isa(SVI->getOperand(2))) - return std::vector(NElts, 0); + return SmallVector(NElts, 0); if (isa(SVI->getOperand(2))) - return std::vector(NElts, -1); + return SmallVector(NElts, -1); - std::vector Result; + SmallVector Result; const ConstantVector *CP = cast(SVI->getOperand(2)); for (User::const_op_iterator i = CP->op_begin(), e = CP->op_end(); i!=e; ++i) if (isa(*i)) @@ -447,7 +447,7 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) { Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { Value *LHS = SVI.getOperand(0); Value *RHS = SVI.getOperand(1); - std::vector Mask = getShuffleMask(&SVI); + SmallVector Mask = getShuffleMask(&SVI); bool MadeChange = false; @@ -457,9 +457,6 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { unsigned VWidth = cast(SVI.getType())->getNumElements(); - if (VWidth != cast(LHS->getType())->getNumElements()) - return 0; - APInt UndefElts(VWidth, 0); APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth)); if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) { @@ -470,17 +467,21 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { MadeChange = true; } + unsigned LHSWidth = cast(LHS->getType())->getNumElements(); + // Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask') // Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask'). if (LHS == RHS || isa(LHS)) { if (isa(LHS) && LHS == RHS) { // shuffle(undef,undef,mask) -> undef. - return ReplaceInstUsesWith(SVI, LHS); + Value* result = (VWidth == LHSWidth) + ? LHS : UndefValue::get(SVI.getType()); + return ReplaceInstUsesWith(SVI, result); } // Remap any references to RHS to use LHS. std::vector Elts; - for (unsigned i = 0, e = Mask.size(); i != e; ++i) { + for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) { if (Mask[i] < 0) Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); else { @@ -503,72 +504,205 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { MadeChange = true; } - // Analyze the shuffle, are the LHS or RHS and identity shuffles? - bool isLHSID = true, isRHSID = true; + if (VWidth == LHSWidth) { + // Analyze the shuffle, are the LHS or RHS and identity shuffles? + bool isLHSID = true, isRHSID = true; + + for (unsigned i = 0, e = Mask.size(); i != e; ++i) { + if (Mask[i] < 0) continue; // Ignore undef values. + // Is this an identity shuffle of the LHS value? + isLHSID &= (Mask[i] == (int)i); - for (unsigned i = 0, e = Mask.size(); i != e; ++i) { - if (Mask[i] < 0) continue; // Ignore undef values. - // Is this an identity shuffle of the LHS value? - isLHSID &= (Mask[i] == (int)i); + // Is this an identity shuffle of the RHS value? + isRHSID &= (Mask[i]-e == i); + } - // Is this an identity shuffle of the RHS value? - isRHSID &= (Mask[i]-e == i); + // Eliminate identity shuffles. + if (isLHSID) return ReplaceInstUsesWith(SVI, LHS); + if (isRHSID) return ReplaceInstUsesWith(SVI, RHS); } - // Eliminate identity shuffles. - if (isLHSID) return ReplaceInstUsesWith(SVI, LHS); - if (isRHSID) return ReplaceInstUsesWith(SVI, RHS); - // If the LHS is a shufflevector itself, see if we can combine it with this - // one without producing an unusual shuffle. Here we are really conservative: + // one without producing an unusual shuffle. + // Cases that might be simplified: + // 1. + // x1=shuffle(v1,v2,mask1) + // x=shuffle(x1,undef,mask) + // ==> + // x=shuffle(v1,undef,newMask) + // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : -1 + // 2. + // x1=shuffle(v1,undef,mask1) + // x=shuffle(x1,x2,mask) + // where v1.size() == mask1.size() + // ==> + // x=shuffle(v1,x2,newMask) + // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : mask[i] + // 3. + // x2=shuffle(v2,undef,mask2) + // x=shuffle(x1,x2,mask) + // where v2.size() == mask2.size() + // ==> + // x=shuffle(x1,v2,newMask) + // newMask[i] = (mask[i] < x1.size()) + // ? mask[i] : mask2[mask[i]-x1.size()]+x1.size() + // 4. + // x1=shuffle(v1,undef,mask1) + // x2=shuffle(v2,undef,mask2) + // x=shuffle(x1,x2,mask) + // where v1.size() == v2.size() + // ==> + // x=shuffle(v1,v2,newMask) + // newMask[i] = (mask[i] < x1.size()) + // ? mask1[mask[i]] : mask2[mask[i]-x1.size()]+v1.size() + // + // Here we are really conservative: // we are absolutely afraid of producing a shuffle mask not in the input // program, because the code gen may not be smart enough to turn a merged // shuffle into two specific shuffles: it may produce worse code. As such, // we only merge two shuffles if the result is either a splat or one of the - // two input shuffle masks. In this case, merging the shuffles just removes + // input shuffle masks. In this case, merging the shuffles just removes // one instruction, which we know is safe. This is good for things like - // turning: (splat(splat)) -> splat. - if (ShuffleVectorInst *LHSSVI = dyn_cast(LHS)) { + // turning: (splat(splat)) -> splat, or + // merge(V[0..n], V[n+1..2n]) -> V[0..2n] + ShuffleVectorInst* LHSShuffle = dyn_cast(LHS); + ShuffleVectorInst* RHSShuffle = dyn_cast(RHS); + if (LHSShuffle) + if (!isa(LHSShuffle->getOperand(1)) && !isa(RHS)) + LHSShuffle = NULL; + if (RHSShuffle) + if (!isa(RHSShuffle->getOperand(1))) + RHSShuffle = NULL; + if (!LHSShuffle && !RHSShuffle) + return MadeChange ? &SVI : 0; + + Value* LHSOp0 = NULL; + Value* LHSOp1 = NULL; + Value* RHSOp0 = NULL; + unsigned LHSOp0Width = 0; + unsigned RHSOp0Width = 0; + if (LHSShuffle) { + LHSOp0 = LHSShuffle->getOperand(0); + LHSOp1 = LHSShuffle->getOperand(1); + LHSOp0Width = cast(LHSOp0->getType())->getNumElements(); + } + if (RHSShuffle) { + RHSOp0 = RHSShuffle->getOperand(0); + RHSOp0Width = cast(RHSOp0->getType())->getNumElements(); + } + Value* newLHS = LHS; + Value* newRHS = RHS; + if (LHSShuffle) { + // case 1 if (isa(RHS)) { - std::vector LHSMask = getShuffleMask(LHSSVI); - - if (LHSMask.size() == Mask.size()) { - std::vector NewMask; - bool isSplat = true; - int SplatElt = -1; // undef - for (unsigned i = 0, e = Mask.size(); i != e; ++i) { - int MaskElt; - if (Mask[i] < 0 || Mask[i] >= (int)e) - MaskElt = -1; // undef - else - MaskElt = LHSMask[Mask[i]]; - // Check if this could still be a splat. - if (MaskElt >= 0) { - if (SplatElt >=0 && SplatElt != MaskElt) - isSplat = false; - SplatElt = MaskElt; - } - NewMask.push_back(MaskElt); - } + newLHS = LHSOp0; + newRHS = LHSOp1; + } + // case 2 or 4 + else if (LHSOp0Width == LHSWidth) { + newLHS = LHSOp0; + } + } + // case 3 or 4 + if (RHSShuffle && RHSOp0Width == LHSWidth) { + newRHS = RHSOp0; + } + // case 4 + if (LHSOp0 == RHSOp0) { + newLHS = LHSOp0; + newRHS = NULL; + } - // If the result mask is equal to the src shuffle or this - // shuffle mask, do the replacement. - if (isSplat || NewMask == LHSMask || NewMask == Mask) { - std::vector Elts; - Type *Int32Ty = Type::getInt32Ty(SVI.getContext()); - for (unsigned i = 0, e = NewMask.size(); i != e; ++i) { - if (NewMask[i] < 0) { - Elts.push_back(UndefValue::get(Int32Ty)); - } else { - Elts.push_back(ConstantInt::get(Int32Ty, NewMask[i])); - } - } - return new ShuffleVectorInst(LHSSVI->getOperand(0), - LHSSVI->getOperand(1), - ConstantVector::get(Elts)); + if (newLHS == LHS && newRHS == RHS) + return MadeChange ? &SVI : 0; + + SmallVector LHSMask; + SmallVector RHSMask; + if (newLHS != LHS) { + LHSMask = getShuffleMask(LHSShuffle); + } + if (RHSShuffle && newRHS != RHS) { + RHSMask = getShuffleMask(RHSShuffle); + } + unsigned newLHSWidth = (newLHS != LHS) ? LHSOp0Width : LHSWidth; + SmallVector newMask; + bool isSplat = true; + int SplatElt = -1; + // Create a new mask for the new ShuffleVectorInst so that the new + // ShuffleVectorInst is equivalent to the original one. + for (unsigned i = 0; i < VWidth; ++i) { + int eltMask; + if (Mask[i] == -1) { + // This element is an undef value. + eltMask = -1; + } else if (Mask[i] < (int)LHSWidth) { + // This element is from left hand side vector operand. + // + // If LHS is going to be replaced (case 1, 2, or 4), calculate the + // new mask value for the element. + if (newLHS != LHS) { + eltMask = LHSMask[Mask[i]]; + // If the value selected is an undef value, explicitly specify it + // with a -1 mask value. + if (eltMask >= (int)LHSOp0Width && isa(LHSOp1)) + eltMask = -1; + } + else + eltMask = Mask[i]; + } else { + // This element is from right hand side vector operand + // + // If the value selected is an undef value, explicitly specify it + // with a -1 mask value. (case 1) + if (isa(RHS)) + eltMask = -1; + // If RHS is going to be replaced (case 3 or 4), calculate the + // new mask value for the element. + else if (newRHS != RHS) { + eltMask = RHSMask[Mask[i]-LHSWidth]; + // If the value selected is an undef value, explicitly specify it + // with a -1 mask value. + if (eltMask >= (int)RHSOp0Width) { + assert(isa(RHSShuffle->getOperand(1)) + && "should have been check above"); + eltMask = -1; } } + else + eltMask = Mask[i]-LHSWidth; + + // If LHS's width is changed, shift the mask value accordingly. + // If newRHS == NULL, i.e. LHSOp0 == RHSOp0, we want to remap any + // references to RHSOp0 to LHSOp0, so we don't need to shift the mask. + if (eltMask >= 0 && newRHS != NULL) + eltMask += newLHSWidth; + } + + // Check if this could still be a splat. + if (eltMask >= 0) { + if (SplatElt >= 0 && SplatElt != eltMask) + isSplat = false; + SplatElt = eltMask; + } + + newMask.push_back(eltMask); + } + + // If the result mask is equal to one of the original shuffle masks, + // or is a splat, do the replacement. + if (isSplat || newMask == LHSMask || newMask == RHSMask || newMask == Mask) { + SmallVector Elts; + Type *Int32Ty = Type::getInt32Ty(SVI.getContext()); + for (unsigned i = 0, e = newMask.size(); i != e; ++i) { + if (newMask[i] < 0) { + Elts.push_back(UndefValue::get(Int32Ty)); + } else { + Elts.push_back(ConstantInt::get(Int32Ty, newMask[i])); + } } + if (newRHS == NULL) + newRHS = UndefValue::get(newLHS->getType()); + return new ShuffleVectorInst(newLHS, newRHS, ConstantVector::get(Elts)); } return MadeChange ? &SVI : 0; diff --git a/test/Transforms/InstCombine/vec_shuffle.ll b/test/Transforms/InstCombine/vec_shuffle.ll index 896cb881760..8f78c2e6bd5 100644 --- a/test/Transforms/InstCombine/vec_shuffle.ll +++ b/test/Transforms/InstCombine/vec_shuffle.ll @@ -98,6 +98,17 @@ define <4 x i8> @test9a(<16 x i8> %tmp6) nounwind { ret <4 x i8> %tmp9 } +; Test fold of two shuffles where the first shuffle vectors inputs are a +; different length then the second. +define <4 x i8> @test9b(<4 x i8> %tmp6, <4 x i8> %tmp7) nounwind { +; CHECK: @test9 +; CHECK-NEXT: shufflevector +; CHECK-NEXT: ret + %tmp1 = shufflevector <4 x i8> %tmp6, <4 x i8> %tmp7, <8 x i32> ; <<4 x i8>> [#uses=1] + %tmp9 = shufflevector <8 x i8> %tmp1, <8 x i8> undef, <4 x i32> ; <<4 x i8>> [#uses=1] + ret <4 x i8> %tmp9 +} + ; Redundant vector splats should be removed. Radar 8597790. define <4 x i32> @test10(<4 x i32> %tmp5) nounwind { ; CHECK: @test10 @@ -107,3 +118,38 @@ define <4 x i32> @test10(<4 x i32> %tmp5) nounwind { %tmp7 = shufflevector <4 x i32> %tmp6, <4 x i32> undef, <4 x i32> zeroinitializer ret <4 x i32> %tmp7 } + +; Test fold of two shuffles where the two shufflevector inputs's op1 are +; the same +define <8 x i8> @test11(<16 x i8> %tmp6) nounwind { +; CHECK: @test11 +; CHECK-NEXT: shufflevector <16 x i8> %tmp6, <16 x i8> undef, <8 x i32> +; CHECK-NEXT: ret + %tmp1 = shufflevector <16 x i8> %tmp6, <16 x i8> undef, <4 x i32> ; <<4 x i8>> [#uses=1] + %tmp2 = shufflevector <16 x i8> %tmp6, <16 x i8> undef, <4 x i32> ; <<4 x i8>> [#uses=1] + %tmp3 = shufflevector <4 x i8> %tmp1, <4 x i8> %tmp2, <8 x i32> ; <<8 x i8>> [#uses=1] + ret <8 x i8> %tmp3 +} + +; Test fold of two shuffles where the first shufflevector's inputs are +; the same as the second +define <8 x i8> @test12(<8 x i8> %tmp6, <8 x i8> %tmp2) nounwind { +; CHECK: @test12 +; CHECK-NEXT: shufflevector <8 x i8> %tmp6, <8 x i8> %tmp2, <8 x i32> +; CHECK-NEXT: ret + %tmp1 = shufflevector <8 x i8> %tmp6, <8 x i8> undef, <8 x i32> ; <<8 x i8>> [#uses=1] + %tmp3 = shufflevector <8 x i8> %tmp1, <8 x i8> %tmp2, <8 x i32> ; <<8 x i8>> [#uses=1] + ret <8 x i8> %tmp3 +} + +; Test fold of two shuffles where the first shufflevector's inputs are +; the same as the second +define <8 x i8> @test12a(<8 x i8> %tmp6, <8 x i8> %tmp2) nounwind { +; CHECK: @test12a +; CHECK-NEXT: shufflevector <8 x i8> %tmp2, <8 x i8> %tmp6, <8 x i32> +; CHECK-NEXT: ret + %tmp1 = shufflevector <8 x i8> %tmp6, <8 x i8> undef, <8 x i32> ; <<8 x i8>> [#uses=1] + %tmp3 = shufflevector <8 x i8> %tmp2, <8 x i8> %tmp1, <8 x i32> ; <<8 x i8>> [#uses=1] + ret <8 x i8> %tmp3 +} +