From a47b56f4ef8355e7c2abf1f10ff2c317d9d6e54a Mon Sep 17 00:00:00 2001 From: Jun Zhang Date: Tue, 16 May 2023 19:11:40 +0800 Subject: [PATCH] [Instsimplfy] X == Y ? 0 : X - Y --> X - Y Alive2: https://alive2.llvm.org/ce/z/rPN1GB Fixes: https://github.com/llvm/llvm-project/issues/62238 Depends on D150377 Signed-off-by: Jun Zhang Differential Revision: https://reviews.llvm.org/D150378 --- llvm/lib/Analysis/InstructionSimplify.cpp | 7 +++++++ llvm/test/Transforms/InstSimplify/select.ll | 24 ++++++++---------------- 2 files changed, 15 insertions(+), 16 deletions(-) diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index fd0ba39..50e3997 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -4256,6 +4256,13 @@ static Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp, NewOps[0] == NewOps[1]) return NewOps[0]; + // x - x -> 0. This is non-refining, because x is non-poison by assumption + // and this case never wraps, so nowrap flags can be ignored. + if (Opcode == Instruction::Sub && NewOps[0] == NewOps[1]) { + assert(NewOps[0] == RepOp && "Precondition for non-poison assumption"); + return Constant::getNullValue(I->getType()); + } + // If we are substituting an absorber constant into a binop and extra // poison can't leak if we remove the select -- because both operands of // the binop are based on the same value -- then it may be safe to replace diff --git a/llvm/test/Transforms/InstSimplify/select.ll b/llvm/test/Transforms/InstSimplify/select.ll index 29c568d..a77e8df 100644 --- a/llvm/test/Transforms/InstSimplify/select.ll +++ b/llvm/test/Transforms/InstSimplify/select.ll @@ -1441,10 +1441,8 @@ exit: define i8 @select_sub_cmp(i8 %0, i8 %1) { ; CHECK-LABEL: @select_sub_cmp( -; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i8 [[TMP1:%.*]], [[TMP0:%.*]] -; CHECK-NEXT: [[TMP4:%.*]] = sub nsw i8 [[TMP1]], [[TMP0]] -; CHECK-NEXT: [[TMP5:%.*]] = select i1 [[TMP3]], i8 0, i8 [[TMP4]] -; CHECK-NEXT: ret i8 [[TMP5]] +; CHECK-NEXT: [[TMP3:%.*]] = sub nsw i8 [[TMP1:%.*]], [[TMP0:%.*]] +; CHECK-NEXT: ret i8 [[TMP3]] ; %3 = icmp eq i8 %1, %0 %4 = sub nsw i8 %1, %0 @@ -1454,10 +1452,8 @@ define i8 @select_sub_cmp(i8 %0, i8 %1) { define <2 x i8> @select_sub_cmp_vec(<2 x i8> %0, <2 x i8> %1) { ; CHECK-LABEL: @select_sub_cmp_vec( -; CHECK-NEXT: [[TMP3:%.*]] = icmp eq <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]] -; CHECK-NEXT: [[TMP4:%.*]] = sub nsw <2 x i8> [[TMP1]], [[TMP0]] -; CHECK-NEXT: [[TMP5:%.*]] = select <2 x i1> [[TMP3]], <2 x i8> zeroinitializer, <2 x i8> [[TMP4]] -; CHECK-NEXT: ret <2 x i8> [[TMP5]] +; CHECK-NEXT: [[TMP3:%.*]] = sub nsw <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]] +; CHECK-NEXT: ret <2 x i8> [[TMP3]] ; %3 = icmp eq <2 x i8> %1, %0 %4 = sub nsw <2 x i8> %1, %0 @@ -1467,10 +1463,8 @@ define <2 x i8> @select_sub_cmp_vec(<2 x i8> %0, <2 x i8> %1) { define i8 @select_sub_cmp_swap(i8 %0, i8 %1) { ; CHECK-LABEL: @select_sub_cmp_swap( -; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i8 [[TMP1:%.*]], [[TMP0:%.*]] -; CHECK-NEXT: [[TMP4:%.*]] = sub nsw i8 [[TMP0]], [[TMP1]] -; CHECK-NEXT: [[TMP5:%.*]] = select i1 [[TMP3]], i8 0, i8 [[TMP4]] -; CHECK-NEXT: ret i8 [[TMP5]] +; CHECK-NEXT: [[TMP3:%.*]] = sub nsw i8 [[TMP0:%.*]], [[TMP1:%.*]] +; CHECK-NEXT: ret i8 [[TMP3]] ; %3 = icmp eq i8 %1, %0 %4 = sub nsw i8 %0, %1 @@ -1480,10 +1474,8 @@ define i8 @select_sub_cmp_swap(i8 %0, i8 %1) { define <2 x i8> @select_sub_cmp_vec_swap(<2 x i8> %0, <2 x i8> %1) { ; CHECK-LABEL: @select_sub_cmp_vec_swap( -; CHECK-NEXT: [[TMP3:%.*]] = icmp eq <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]] -; CHECK-NEXT: [[TMP4:%.*]] = sub nsw <2 x i8> [[TMP0]], [[TMP1]] -; CHECK-NEXT: [[TMP5:%.*]] = select <2 x i1> [[TMP3]], <2 x i8> zeroinitializer, <2 x i8> [[TMP4]] -; CHECK-NEXT: ret <2 x i8> [[TMP5]] +; CHECK-NEXT: [[TMP3:%.*]] = sub nsw <2 x i8> [[TMP0:%.*]], [[TMP1:%.*]] +; CHECK-NEXT: ret <2 x i8> [[TMP3]] ; %3 = icmp eq <2 x i8> %1, %0 %4 = sub nsw <2 x i8> %0, %1 -- 2.7.4