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[InstCombine] fold icmp with add/sub instructions having the same operands (#143241)
Closes #143211.
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‎llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

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@@ -7728,6 +7728,30 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
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}
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}
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// icmp slt (sub nsw x, y), (add nsw x, y) --> icmp sgt y, 0
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// icmp ult (sub nuw x, y), (add nuw x, y) --> icmp ugt y, 0
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// icmp eq (sub nsw/nuw x, y), (add nsw/nuw x, y) --> icmp eq y, 0
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{
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Value *A, *B;
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CmpPredicate CmpPred;
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if (match(&I, m_c_ICmp(CmpPred, m_Sub(m_Value(A), m_Value(B)),
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m_c_Add(m_Deferred(A), m_Deferred(B))))) {
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auto *I0 = cast<OverflowingBinaryOperator>(Op0);
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auto *I1 = cast<OverflowingBinaryOperator>(Op1);
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bool I0NUW = I0->hasNoUnsignedWrap();
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bool I1NUW = I1->hasNoUnsignedWrap();
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bool I0NSW = I0->hasNoSignedWrap();
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bool I1NSW = I1->hasNoSignedWrap();
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if ((ICmpInst::isUnsigned(Pred) && I0NUW && I1NUW) ||
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(ICmpInst::isSigned(Pred) && I0NSW && I1NSW) ||
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(ICmpInst::isEquality(Pred) &&
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((I0NUW || I0NSW) && (I1NUW || I1NSW)))) {
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return new ICmpInst(CmpPredicate::getSwapped(CmpPred), B,
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ConstantInt::get(Op0->getType(), 0));
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}
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}
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}
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// Try to optimize equality comparisons against alloca-based pointers.
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if (Op0->getType()->isPointerTy() && I.isEquality()) {
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assert(Op1->getType()->isPointerTy() &&

‎llvm/test/Transforms/InstCombine/icmp-subadd.ll

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@@ -0,0 +1,111 @@
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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define i1 @test-same-operands-sub-add-nsw-icmp-sgt(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-same-operands-sub-add-nsw-icmp-sgt(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[B]], 0
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%sub = sub nsw i8 %a, %b
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%add = add nsw i8 %a, %b
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%cmp = icmp sgt i8 %sub, %add
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ret i1 %cmp
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}
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define i1 @test-same-operands-sub-add-nsw-icmp-slt(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-same-operands-sub-add-nsw-icmp-slt(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[B]], 0
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%sub = sub nsw i8 %a, %b
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%add = add nsw i8 %a, %b
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%cmp = icmp slt i8 %sub, %add
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ret i1 %cmp
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}
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define i1 @test-same-operands-sub-add-nsw-icmp-sle(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-same-operands-sub-add-nsw-icmp-sle(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[B]], -1
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%sub = sub nsw i8 %a, %b
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%add = add nsw i8 %a, %b
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%cmp = icmp sle i8 %sub, %add
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ret i1 %cmp
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}
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define i1 @test-same-operands-sub-add-nsw-nuw-icmp-eq(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-same-operands-sub-add-nsw-nuw-icmp-eq(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[B]], 0
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%sub = sub nsw i8 %a, %b
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%add = add nuw i8 %a, %b
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%cmp = icmp eq i8 %sub, %add
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ret i1 %cmp
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}
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define i1 @test-same-operands-sub-add-nsw-icmp-eq(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-same-operands-sub-add-nsw-icmp-eq(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[B]], 0
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%sub = sub nsw i8 %a, %b
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%add = add nsw i8 %a, %b
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%cmp = icmp eq i8 %sub, %add
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ret i1 %cmp
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}
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define i1 @test-add-sub-nsw-icmp-sgt(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-add-sub-nsw-icmp-sgt(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[B]], 0
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%sub = sub nsw i8 %a, %b
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%add = add nsw i8 %a, %b
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%cmp = icmp sgt i8 %add, %sub
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ret i1 %cmp
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}
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define i1 @test-add-sub-nuw-icmp-uge(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-add-sub-nuw-icmp-uge(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: ret i1 true
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;
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%sub = sub nuw i8 %a, %b
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%add = add nuw i8 %a, %b
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%cmp = icmp uge i8 %add, %sub
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ret i1 %cmp
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}
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; Check not folded
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define i1 @test-add-sub-nuw-icmp-sge(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-add-sub-nuw-icmp-sge(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: [[SUB:%.*]] = sub nuw i8 [[A]], [[B]]
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; CHECK-NEXT: [[ADD:%.*]] = add nuw i8 [[A]], [[B]]
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; CHECK-NEXT: [[CMP:%.*]] = icmp sge i8 [[ADD]], [[SUB]]
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%sub = sub nuw i8 %a, %b
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%add = add nuw i8 %a, %b
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%cmp = icmp sge i8 %add, %sub
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ret i1 %cmp
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}
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define i1 @test-add-swap-sub-nuw-icmp-uge(i8 %a, i8 %b) {
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; CHECK-LABEL: define i1 @test-add-swap-sub-nuw-icmp-uge(
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; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
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; CHECK-NEXT: ret i1 true
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;
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%sub = sub nuw i8 %a, %b
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%add = add nuw i8 %b, %a
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%cmp = icmp uge i8 %add, %sub
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ret i1 %cmp
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}

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