From e6b48a1b02124ac4854defa152fc31fe225f4c49 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Thu, 31 Aug 2017 15:57:17 +0000 Subject: [PATCH] [InstCombine] improve demanded vector elements analysis of insertelement Recurse instead of returning on the first found optimization. Also, return early in the caller instead of continuing because that allows another round of simplification before we might potentially lose undef information from a shuffle mask by eliminating the shuffle. As noted in the review, we could probably do better and be more efficient by moving all of demanded elements into a separate pass, but this is yet another quick fix to instcombine. Differential Revision: https://reviews.llvm.org/D37236 llvm-svn: 312248 --- .../InstCombineSimplifyDemanded.cpp | 19 ++++++++++--------- .../InstCombine/InstCombineVectorOps.cpp | 4 +--- .../Transforms/InstCombine/X86/x86-pshufb.ll | 5 ++--- .../InstCombine/vec_demanded_elts.ll | 17 ++++++----------- 4 files changed, 19 insertions(+), 26 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index cda2ce6c91cb..7d5d28f6fc48 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -993,22 +993,23 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts, break; } + // The element inserted overwrites whatever was there, so the input demanded + // set is simpler than the output set. + unsigned IdxNo = Idx->getZExtValue(); + APInt PreInsertDemandedElts = DemandedElts; + if (IdxNo < VWidth) + PreInsertDemandedElts.clearBit(IdxNo); + TmpV = SimplifyDemandedVectorElts(I->getOperand(0), PreInsertDemandedElts, + UndefElts, Depth + 1); + if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; } + // If this is inserting an element that isn't demanded, remove this // insertelement. - unsigned IdxNo = Idx->getZExtValue(); if (IdxNo >= VWidth || !DemandedElts[IdxNo]) { Worklist.Add(I); return I->getOperand(0); } - // Otherwise, the element inserted overwrites whatever was there, so the - // input demanded set is simpler than the output set. - APInt DemandedElts2 = DemandedElts; - DemandedElts2.clearBit(IdxNo); - TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts2, - UndefElts, Depth + 1); - if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; } - // The inserted element is defined. UndefElts.clearBit(IdxNo); break; diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp index 7380ec21caed..0d327795acf3 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp @@ -1165,9 +1165,7 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) { if (V != &SVI) return replaceInstUsesWith(SVI, V); - LHS = SVI.getOperand(0); - RHS = SVI.getOperand(1); - MadeChange = true; + return &SVI; } unsigned LHSWidth = LHS->getType()->getVectorNumElements(); diff --git a/llvm/test/Transforms/InstCombine/X86/x86-pshufb.ll b/llvm/test/Transforms/InstCombine/X86/x86-pshufb.ll index f181ef57fe20..d3ffd1780109 100644 --- a/llvm/test/Transforms/InstCombine/X86/x86-pshufb.ll +++ b/llvm/test/Transforms/InstCombine/X86/x86-pshufb.ll @@ -485,9 +485,8 @@ define <16 x i8> @demanded_elts_insertion(<16 x i8> %InVec, <16 x i8> %BaseMask, define <32 x i8> @demanded_elts_insertion_avx2(<32 x i8> %InVec, <32 x i8> %BaseMask, i8 %M0, i8 %M22) { ; CHECK-LABEL: @demanded_elts_insertion_avx2( -; CHECK-NEXT: [[TMP1:%.*]] = insertelement <32 x i8> %BaseMask, i8 %M0, i32 0 -; CHECK-NEXT: [[TMP2:%.*]] = tail call <32 x i8> @llvm.x86.avx2.pshuf.b(<32 x i8> %InVec, <32 x i8> [[TMP1]]) -; CHECK-NEXT: ret <32 x i8> [[TMP2]] +; CHECK-NEXT: [[TMP1:%.*]] = tail call <32 x i8> @llvm.x86.avx2.pshuf.b(<32 x i8> %InVec, <32 x i8> %BaseMask) +; CHECK-NEXT: ret <32 x i8> [[TMP1]] ; %1 = insertelement <32 x i8> %BaseMask, i8 %M0, i32 0 %2 = insertelement <32 x i8> %1, i8 %M22, i32 22 diff --git a/llvm/test/Transforms/InstCombine/vec_demanded_elts.ll b/llvm/test/Transforms/InstCombine/vec_demanded_elts.ll index bc935c89bb9a..9d59efbad738 100644 --- a/llvm/test/Transforms/InstCombine/vec_demanded_elts.ll +++ b/llvm/test/Transforms/InstCombine/vec_demanded_elts.ll @@ -142,13 +142,11 @@ define <2 x i64> @PR24922(<2 x i64> %v) { ret <2 x i64> %result } -; FIXME: The shuffle only demands the 0th (undef) element of 'out123', so everything should fold away. +; The shuffle only demands the 0th (undef) element of 'out123', so everything should fold away. define <4 x float> @inselt_shuf_no_demand(float %a1, float %a2, float %a3) { ; CHECK-LABEL: @inselt_shuf_no_demand( -; CHECK-NEXT: [[OUT1:%.*]] = insertelement <4 x float> undef, float %a1, i32 1 -; CHECK-NEXT: [[OUT12:%.*]] = insertelement <4 x float> [[OUT1]], float %a2, i32 2 -; CHECK-NEXT: ret <4 x float> [[OUT12]] +; CHECK-NEXT: ret <4 x float> undef ; %out1 = insertelement <4 x float> undef, float %a1, i32 1 %out12 = insertelement <4 x float> %out1, float %a2, i32 2 @@ -157,13 +155,11 @@ define <4 x float> @inselt_shuf_no_demand(float %a1, float %a2, float %a3) { ret <4 x float> %shuffle } -; FIXME: The shuffle only demands the 0th (undef) element of 'out123', so everything should fold away. +; The shuffle only demands the 0th (undef) element of 'out123', so everything should fold away. define <4 x float> @inselt_shuf_no_demand_commute(float %a1, float %a2, float %a3) { ; CHECK-LABEL: @inselt_shuf_no_demand_commute( -; CHECK-NEXT: [[OUT1:%.*]] = insertelement <4 x float> undef, float %a1, i32 1 -; CHECK-NEXT: [[OUT12:%.*]] = insertelement <4 x float> [[OUT1]], float %a2, i32 2 -; CHECK-NEXT: ret <4 x float> [[OUT12]] +; CHECK-NEXT: ret <4 x float> undef ; %out1 = insertelement <4 x float> undef, float %a1, i32 1 %out12 = insertelement <4 x float> %out1, float %a2, i32 2 @@ -172,15 +168,14 @@ define <4 x float> @inselt_shuf_no_demand_commute(float %a1, float %a2, float %a ret <4 x float> %shuffle } -; FIXME: The add uses 'out012' giving it multiple uses after the shuffle is transformed to also +; The add uses 'out012' giving it multiple uses after the shuffle is transformed to also ; use 'out012'. The analysis should be able to see past that. define <4 x i32> @inselt_shuf_no_demand_multiuse(i32 %a0, i32 %a1, <4 x i32> %b) { ; CHECK-LABEL: @inselt_shuf_no_demand_multiuse( ; CHECK-NEXT: [[OUT0:%.*]] = insertelement <4 x i32> undef, i32 %a0, i32 0 ; CHECK-NEXT: [[OUT01:%.*]] = insertelement <4 x i32> [[OUT0]], i32 %a1, i32 1 -; CHECK-NEXT: [[OUT012:%.*]] = insertelement <4 x i32> [[OUT01]], i32 %a0, i32 2 -; CHECK-NEXT: [[FOO:%.*]] = add <4 x i32> [[OUT012]], %b +; CHECK-NEXT: [[FOO:%.*]] = add <4 x i32> [[OUT01]], %b ; CHECK-NEXT: ret <4 x i32> [[FOO]] ; %out0 = insertelement <4 x i32> undef, i32 %a0, i32 0