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[CVP] Stop CVP constant propagation from destroying llvm.assume #183688

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Merged
nikic merged 1 commit into from
Mar 2, 2026
Merged

[CVP] Stop CVP constant propagation from destroying llvm.assume #183688

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15 changes: 11 additions & 4 deletions llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -333,10 +333,17 @@ static bool constantFoldCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
if (!Res)
return false;

++NumCmps;
Cmp->replaceAllUsesWith(Res);
Cmp->eraseFromParent();
return true;
bool Changed = Cmp->replaceUsesWithIf(
Res, [](Use &U) { return !isa<AssumeInst>(U.getUser()); });
if (Cmp->use_empty()) {
Cmp->eraseFromParent();
Changed = true;
}

if (Changed)
++NumCmps;

return Changed;
}

static bool processCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
Expand Down
3 changes: 2 additions & 1 deletion llvm/test/Transforms/CorrelatedValuePropagation/conflict.ll
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Expand Up @@ -58,7 +58,8 @@ define i8 @test3(i8 %a) {
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i8 [[A:%.*]], 5
; CHECK-NEXT: br i1 [[CMP1]], label [[DEAD:%.*]], label [[EXIT:%.*]]
; CHECK: dead:
; CHECK-NEXT: call void @llvm.assume(i1 false)
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i8 [[A]], 3
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP2]])
; CHECK-NEXT: ret i8 5
; CHECK: exit:
; CHECK-NEXT: ret i8 0
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18 changes: 18 additions & 0 deletions llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
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Expand Up @@ -6,6 +6,7 @@ target triple = "x86_64-apple-macosx10.10.0"

declare void @check1(i1) #1
declare void @check2(i1) #1
declare void @check3(i64)
declare void @llvm.assume(i1)

; Make sure we propagate the value of %tmp35 to the true/false cases
Expand Down Expand Up @@ -1657,3 +1658,20 @@ if.true:
if.false:
ret void
}

define void @test_assume_not_removed(i64 %idx) {
; CHECK-LABEL: @test_assume_not_removed(
; CHECK-NEXT: [[IDX1:%.*]] = add nuw i64 [[IDX:%.*]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[IDX1]], 1
; CHECK-NEXT: tail call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: tail call void @check3(i64 [[IDX1]])
; CHECK-NEXT: tail call void @check1(i1 true)
; CHECK-NEXT: ret void
;
%idx1 = add i64 %idx, 1
%cmp = icmp ugt i64 %idx1, 1
tail call void @llvm.assume(i1 %cmp)
tail call void @check3(i64 %idx1)
tail call void @check1(i1 %cmp)
ret void
}
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