From d640641a61ea316ba16ccf4378c97cf48d10c40d Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Thu, 15 Dec 2016 19:13:37 +0000 Subject: [PATCH] [InstCombine] add folds for icmp (smin X, Y), X Min/max canonicalization (r287585) exposes the fact that we're missing combines for min/max patterns. This patch won't solve the example that was attached to that thread, so something else still needs fixing. The line between InstCombine and InstSimplify gets blurry here because sometimes the icmp instruction that we want to fold to already exists, but sometimes it's the swapped form of what we want. Corresponding changes for smax/umin/umax to follow. Differential Revision: https://reviews.llvm.org/D27531 llvm-svn: 289855 --- llvm/include/llvm/IR/PatternMatch.h | 10 ++++ .../InstCombine/InstCombineCompares.cpp | 37 ++++++++++++++ llvm/test/Transforms/InstCombine/smin-icmp.ll | 48 +++++-------------- 3 files changed, 59 insertions(+), 36 deletions(-) diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h index 9151afd2295f..9b18850a54d0 100644 --- a/llvm/include/llvm/IR/PatternMatch.h +++ b/llvm/include/llvm/IR/PatternMatch.h @@ -1349,6 +1349,16 @@ m_c_Xor(const LHS &L, const RHS &R) { return m_CombineOr(m_Xor(L, R), m_Xor(R, L)); } +// TODO: Add the related SMax, UMax, UMin commuted matchers. + +/// Matches an SMin with LHS and RHS in either order. +template +inline match_combine_or, + MaxMin_match> +m_c_SMin(const LHS &L, const RHS &R) { + return m_CombineOr(m_SMin(L, R), m_SMin(R, L)); +} + } // end namespace PatternMatch } // end namespace llvm diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 844b9b6ae28f..9ffb47efbfbc 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3030,6 +3030,40 @@ Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) { return nullptr; } +/// Fold icmp Pred smin(X, Y), X. +static Instruction *foldICmpWithSMin(ICmpInst &Cmp) { + ICmpInst::Predicate Pred = Cmp.getPredicate(); + Value *Op0 = Cmp.getOperand(0); + Value *X = Cmp.getOperand(1); + + // TODO: This should be expanded to handle smax/umax/umin. + + // Canonicalize minimum operand to LHS of the icmp. + if (match(X, m_c_SMin(m_Specific(Op0), m_Value()))) { + std::swap(Op0, X); + Pred = Cmp.getSwappedPredicate(); + } + + Value *Y; + if (!match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) + return nullptr; + + // smin(X, Y) == X --> X <= Y + // smin(X, Y) >= X --> X <= Y + if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE) + return new ICmpInst(ICmpInst::ICMP_SLE, X, Y); + + // smin(X, Y) != X --> X > Y + // smin(X, Y) < X --> X > Y + if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT) + return new ICmpInst(ICmpInst::ICMP_SGT, X, Y); + + // These cases should be handled in InstSimplify: + // smin(X, Y) <= X --> true + // smin(X, Y) > X --> false + return nullptr; +} + Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) { if (!I.isEquality()) return nullptr; @@ -4277,6 +4311,9 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { if (Instruction *Res = foldICmpBinOp(I)) return Res; + if (Instruction *Res = foldICmpWithSMin(I)) + return Res; + { Value *A, *B; // Transform (A & ~B) == 0 --> (A & B) != 0 diff --git a/llvm/test/Transforms/InstCombine/smin-icmp.ll b/llvm/test/Transforms/InstCombine/smin-icmp.ll index 083d06390268..b3e375fdcddc 100644 --- a/llvm/test/Transforms/InstCombine/smin-icmp.ll +++ b/llvm/test/Transforms/InstCombine/smin-icmp.ll @@ -11,9 +11,7 @@ define i1 @eq_smin1(i32 %x, i32 %y) { ; CHECK-LABEL: @eq_smin1( -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %x, %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y -; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[SEL]], %x +; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 %x, %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %cmp1 = icmp slt i32 %x, %y @@ -26,9 +24,7 @@ define i1 @eq_smin1(i32 %x, i32 %y) { define i1 @eq_smin2(i32 %x, i32 %y) { ; CHECK-LABEL: @eq_smin2( -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %y, %x -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 %x -; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[SEL]], %x +; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 %x, %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %cmp1 = icmp slt i32 %y, %x @@ -42,9 +38,7 @@ define i1 @eq_smin2(i32 %x, i32 %y) { define i1 @eq_smin3(i32 %a, i32 %y) { ; CHECK-LABEL: @eq_smin3( ; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3 -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[X]], %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y -; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[X]], [[SEL]] +; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %x = add i32 %a, 3 ; thwart complexity-based canonicalization @@ -59,9 +53,7 @@ define i1 @eq_smin3(i32 %a, i32 %y) { define i1 @eq_smin4(i32 %a, i32 %y) { ; CHECK-LABEL: @eq_smin4( ; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3 -; CHECK-NEXT: [[CMP1:%.*]] = icmp sgt i32 [[X]], %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 [[X]] -; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[X]], [[SEL]] +; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %x = add i32 %a, 3 ; thwart complexity-based canonicalization @@ -75,9 +67,7 @@ define i1 @eq_smin4(i32 %a, i32 %y) { define i1 @sge_smin1(i32 %x, i32 %y) { ; CHECK-LABEL: @sge_smin1( -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %x, %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y -; CHECK-NEXT: [[CMP2:%.*]] = icmp sge i32 [[SEL]], %x +; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 %x, %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %cmp1 = icmp slt i32 %x, %y @@ -90,9 +80,7 @@ define i1 @sge_smin1(i32 %x, i32 %y) { define i1 @sge_smin2(i32 %x, i32 %y) { ; CHECK-LABEL: @sge_smin2( -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %y, %x -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 %x -; CHECK-NEXT: [[CMP2:%.*]] = icmp sge i32 [[SEL]], %x +; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 %x, %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %cmp1 = icmp slt i32 %y, %x @@ -106,9 +94,7 @@ define i1 @sge_smin2(i32 %x, i32 %y) { define i1 @sge_smin3(i32 %a, i32 %y) { ; CHECK-LABEL: @sge_smin3( ; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3 -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[X]], %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y -; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], [[SEL]] +; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %x = add i32 %a, 3 ; thwart complexity-based canonicalization @@ -123,9 +109,7 @@ define i1 @sge_smin3(i32 %a, i32 %y) { define i1 @sge_smin4(i32 %a, i32 %y) { ; CHECK-LABEL: @sge_smin4( ; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3 -; CHECK-NEXT: [[CMP1:%.*]] = icmp sgt i32 [[X]], %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 [[X]] -; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], [[SEL]] +; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %x = add i32 %a, 3 ; thwart complexity-based canonicalization @@ -139,9 +123,7 @@ define i1 @sge_smin4(i32 %a, i32 %y) { define i1 @ne_smin1(i32 %x, i32 %y) { ; CHECK-LABEL: @ne_smin1( -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %x, %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y -; CHECK-NEXT: [[CMP2:%.*]] = icmp ne i32 [[SEL]], %x +; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 %x, %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %cmp1 = icmp slt i32 %x, %y @@ -168,9 +150,7 @@ define i1 @ne_smin2(i32 %x, i32 %y) { define i1 @ne_smin3(i32 %a, i32 %y) { ; CHECK-LABEL: @ne_smin3( ; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3 -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[X]], %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y -; CHECK-NEXT: [[CMP2:%.*]] = icmp ne i32 [[X]], [[SEL]] +; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %x = add i32 %a, 3 ; thwart complexity-based canonicalization @@ -199,9 +179,7 @@ define i1 @ne_smin4(i32 %a, i32 %y) { define i1 @slt_smin1(i32 %x, i32 %y) { ; CHECK-LABEL: @slt_smin1( -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %x, %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y -; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i32 [[SEL]], %x +; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 %x, %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %cmp1 = icmp slt i32 %x, %y @@ -228,9 +206,7 @@ define i1 @slt_smin2(i32 %x, i32 %y) { define i1 @slt_smin3(i32 %a, i32 %y) { ; CHECK-LABEL: @slt_smin3( ; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3 -; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[X]], %y -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y -; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], [[SEL]] +; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], %y ; CHECK-NEXT: ret i1 [[CMP2]] ; %x = add i32 %a, 3 ; thwart complexity-based canonicalization