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[NFC] [IndVarSimplify] Add non-overflowing usub test #159683

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Merged
merged 3 commits into from
Sep 21, 2025
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[NFC] [IndVarSimplify] Add non-overflowing usub test #159683

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bbcb10a
[𝘀𝗽𝗿] initial version
fmayer Sep 19, 2025
f77fa7f
address
fmayer Sep 19, 2025
bc6bf5e
fixup
fmayer Sep 19, 2025
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31 changes: 31 additions & 0 deletions llvm/test/Transforms/IndVarSimplify/X86/overflow-intrinsics.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -109,6 +109,37 @@ for.body: ; preds = %entry, %cont
%0 = tail call { i32, i1 } @llvm.usub.with.overflow.i32(i32 %i.04, i32 1)
%1 = extractvalue { i32, i1 } %0, 1

; CHECK: for.body:
; CHECK-NOT: @llvm.usub.with.overflow.i32
; CHECK: br i1 false, label %trap, label %cont, !nosanitize !0
br i1 %1, label %trap, label %cont, !nosanitize !{}

trap: ; preds = %for.body
tail call void @llvm.trap(), !nosanitize !{}
unreachable, !nosanitize !{}

cont: ; preds = %for.body
%2 = extractvalue { i32, i1 } %0, 0
%cmp = icmp sgt i32 %2, 0
br i1 %cmp, label %for.body, label %for.cond.cleanup
}

define void @f_usub_overflow(ptr nocapture %a) {
; CHECK-LABEL: @f_usub_overflow(
entry:
br label %for.body

for.cond.cleanup: ; preds = %cont
ret void

for.body: ; preds = %entry, %cont
%i.04 = phi i32 [ 15, %entry ], [ %2, %cont ]
%idxprom = sext i32 %i.04 to i64
%arrayidx = getelementptr inbounds i8, ptr %a, i64 %idxprom
store i8 0, ptr %arrayidx, align 1
%0 = tail call { i32, i1 } @llvm.usub.with.overflow.i32(i32 %i.04, i32 1)
%1 = extractvalue { i32, i1 } %0, 1

; It is theoretically possible to prove this, but SCEV cannot
; represent non-unsigned-wrapping subtraction operations.

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