From 98bfa63a658ce09fb37625a6c92bf0de0338f91b Mon Sep 17 00:00:00 2001 From: Noah Goldstein Date: Sun, 7 Apr 2024 14:40:21 -0500 Subject: [PATCH 1/2] [InstCombine] Add tests for folding `(icmp eq/ne (add nuw x, y), 0)`; NFC --- llvm/test/Transforms/InstCombine/icmp-add.ll | 24 ++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/llvm/test/Transforms/InstCombine/icmp-add.ll b/llvm/test/Transforms/InstCombine/icmp-add.ll index b99ed20d7d431c..6f990890dbb2cf 100644 --- a/llvm/test/Transforms/InstCombine/icmp-add.ll +++ b/llvm/test/Transforms/InstCombine/icmp-add.ll @@ -3003,4 +3003,28 @@ define i1 @icmp_dec_notnonzero(i8 %x) { ret i1 %c } +define i1 @icmp_addnuw_nonzero(i8 %x, i8 %y) { +; CHECK-LABEL: @icmp_addnuw_nonzero( +; CHECK-NEXT: [[I:%.*]] = sub i8 0, [[Y:%.*]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[I]], [[X:%.*]] +; CHECK-NEXT: ret i1 [[C]] +; + %i = add nuw i8 %x, %y + %c = icmp eq i8 %i, 0 + ret i1 %c +} + +define i1 @icmp_addnuw_nonzero_fail_multiuse(i32 %x, i32 %y) { +; CHECK-LABEL: @icmp_addnuw_nonzero_fail_multiuse( +; CHECK-NEXT: [[I:%.*]] = add nuw i32 [[X:%.*]], [[Y:%.*]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i32 [[I]], 0 +; CHECK-NEXT: call void @use(i32 [[I]]) +; CHECK-NEXT: ret i1 [[C]] +; + %i = add nuw i32 %x, %y + %c = icmp eq i32 %i, 0 + call void @use(i32 %i) + ret i1 %c +} + declare void @llvm.assume(i1) From 08ea7f35cf9602e9e0de91e31e989e7a46dfb9fb Mon Sep 17 00:00:00 2001 From: Noah Goldstein Date: Sun, 7 Apr 2024 14:38:03 -0500 Subject: [PATCH 2/2] [InstCombine] Fold `(icmp eq/ne (add nuw x, y), 0)` -> `(icmp eq/ne (or x, y), 0)` `(icmp eq/ne (or x, y), 0)` is probably easier to analyze than `(icmp eq/ne x, -y)` Proof: https://alive2.llvm.org/ce/z/2-VTb6 --- .../InstCombine/InstCombineCompares.cpp | 5 +++++ llvm/test/Transforms/InstCombine/icmp-add.ll | 16 ++++++---------- 2 files changed, 11 insertions(+), 10 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index db302d7e526844..53aa84d53f3085 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3453,6 +3453,11 @@ Instruction *InstCombinerImpl::foldICmpBinOpEqualityWithConstant( if (Value *NegVal = dyn_castNegVal(BOp0)) return new ICmpInst(Pred, NegVal, BOp1); if (BO->hasOneUse()) { + // (add nuw A, B) != 0 -> (or A, B) != 0 + if (match(BO, m_NUWAdd(m_Value(), m_Value()))) { + Value *Or = Builder.CreateOr(BOp0, BOp1); + return new ICmpInst(Pred, Or, Constant::getNullValue(BO->getType())); + } Value *Neg = Builder.CreateNeg(BOp1); Neg->takeName(BO); return new ICmpInst(Pred, BOp0, Neg); diff --git a/llvm/test/Transforms/InstCombine/icmp-add.ll b/llvm/test/Transforms/InstCombine/icmp-add.ll index 6f990890dbb2cf..6b4e5a5372c523 100644 --- a/llvm/test/Transforms/InstCombine/icmp-add.ll +++ b/llvm/test/Transforms/InstCombine/icmp-add.ll @@ -9,10 +9,8 @@ declare void @use(i32) define i1 @cvt_icmp_0_zext_plus_zext_eq_i16(i16 %arg, i16 %arg1) { ; CHECK-LABEL: @cvt_icmp_0_zext_plus_zext_eq_i16( ; CHECK-NEXT: bb: -; CHECK-NEXT: [[I:%.*]] = zext i16 [[ARG:%.*]] to i32 -; CHECK-NEXT: [[I2:%.*]] = zext i16 [[ARG1:%.*]] to i32 -; CHECK-NEXT: [[I3:%.*]] = sub nsw i32 0, [[I]] -; CHECK-NEXT: [[I4:%.*]] = icmp eq i32 [[I2]], [[I3]] +; CHECK-NEXT: [[TMP0:%.*]] = or i16 [[ARG1:%.*]], [[ARG:%.*]] +; CHECK-NEXT: [[I4:%.*]] = icmp eq i16 [[TMP0]], 0 ; CHECK-NEXT: ret i1 [[I4]] ; bb: @@ -27,10 +25,8 @@ bb: define i1 @cvt_icmp_0_zext_plus_zext_eq_i8(i8 %arg, i8 %arg1) { ; CHECK-LABEL: @cvt_icmp_0_zext_plus_zext_eq_i8( ; CHECK-NEXT: bb: -; CHECK-NEXT: [[I:%.*]] = zext i8 [[ARG:%.*]] to i32 -; CHECK-NEXT: [[I2:%.*]] = zext i8 [[ARG1:%.*]] to i32 -; CHECK-NEXT: [[I3:%.*]] = sub nsw i32 0, [[I]] -; CHECK-NEXT: [[I4:%.*]] = icmp eq i32 [[I2]], [[I3]] +; CHECK-NEXT: [[TMP0:%.*]] = or i8 [[ARG1:%.*]], [[ARG:%.*]] +; CHECK-NEXT: [[I4:%.*]] = icmp eq i8 [[TMP0]], 0 ; CHECK-NEXT: ret i1 [[I4]] ; bb: @@ -3005,8 +3001,8 @@ define i1 @icmp_dec_notnonzero(i8 %x) { define i1 @icmp_addnuw_nonzero(i8 %x, i8 %y) { ; CHECK-LABEL: @icmp_addnuw_nonzero( -; CHECK-NEXT: [[I:%.*]] = sub i8 0, [[Y:%.*]] -; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[I]], [[X:%.*]] +; CHECK-NEXT: [[TMP1:%.*]] = or i8 [[X:%.*]], [[Y:%.*]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[TMP1]], 0 ; CHECK-NEXT: ret i1 [[C]] ; %i = add nuw i8 %x, %y