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[InstCombine] Fold (trunc nuw A to i1) == (trunc nuw B to i1) to A == B #133368

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Merged
merged 2 commits into from
Mar 28, 2025
Merged

[InstCombine] Fold (trunc nuw A to i1) == (trunc nuw B to i1) to A == B #133368

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Add Test
veera-sivarajan Mar 28, 2025
ed615d2
[InstCombine] Fold `(trunc nuw A to i1) == (trunc nuw B to i1)` to `A…
veera-sivarajan Mar 28, 2025
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6 changes: 3 additions & 3 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7451,6 +7451,9 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
}
}

if (Instruction *Res = foldICmpTruncWithTruncOrExt(I, Q))
return Res;

if (Op0->getType()->isIntOrIntVectorTy(1))
if (Instruction *Res = canonicalizeICmpBool(I, Builder))
return Res;
Expand All @@ -7473,9 +7476,6 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
if (Instruction *Res = foldICmpUsingKnownBits(I))
return Res;

if (Instruction *Res = foldICmpTruncWithTruncOrExt(I, Q))
return Res;

// Test if the ICmpInst instruction is used exclusively by a select as
// part of a minimum or maximum operation. If so, refrain from doing
// any other folding. This helps out other analyses which understand
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11 changes: 11 additions & 0 deletions llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll
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Expand Up @@ -409,6 +409,17 @@ define i1 @trunc_equality_either(i16 %x, i16 %y) {
ret i1 %c
}

define i1 @trunc_equality_bool(i8 %a, i8 %b) {
; CHECK-LABEL: @trunc_equality_bool(
; CHECK-NEXT: [[EQ:%.*]] = icmp eq i8 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: ret i1 [[EQ]]
;
%at = trunc nuw i8 %a to i1
%bt = trunc nuw i8 %b to i1
%eq = icmp eq i1 %at, %bt
ret i1 %eq
}

define i1 @trunc_unsigned_nuw_zext(i32 %x, i8 %y) {
; CHECK-LABEL: @trunc_unsigned_nuw_zext(
; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32
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