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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - with.overflow intrinsics not removed for arithmetic that trivially cannot overflow"
href="http://llvm.org/bugs/show_bug.cgi?id=20194">20194</a>
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<th>Summary</th>
<td>with.overflow intrinsics not removed for arithmetic that trivially cannot overflow
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>richard-llvm@metafoo.co.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following IR contains a 'llvm.sadd.with.overflow.i32' intrinsic that
trivially cannot ever overflow. We're unable to optimize out the overflow
check.
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@min = common global i8 0, align 1
; Function Attrs: nounwind uwtable
define i32 @main() #0 {
entry:
%0 = load i8* @min, align 1, !tbaa !1
%conv = sext i8 %0 to i32
%1 = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %conv, i32 %conv)
%2 = extractvalue { i32, i1 } %1, 1
br i1 %2, label %trap, label %cont
trap: ; preds = %entry
tail call void @llvm.trap() #2
unreachable
cont: ; preds = %entry
%3 = extractvalue { i32, i1 } %1, 0
ret i32 %3
}
; Function Attrs: nounwind readnone
declare { i32, i1 } @llvm.sadd.with.overflow.i32(i32, i32) #1
; Function Attrs: noreturn nounwind
declare void @llvm.trap() #2
attributes #0 = { nounwind uwtable "less-precise-fpmad"="false"
"no-frame-pointer-elim"="false" "no-infs-fp-math"="false"
"no-nans-fp-math"="false" "stack-protector-buffer-size"="8"
"unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind readnone }
attributes #2 = { noreturn nounwind }
!llvm.ident = !{!0}
!0 = metadata !{metadata !"clang version 3.5.0 (211898)"}
!1 = metadata !{metadata !2, metadata !2, i64 0}
!2 = metadata !{metadata !"omnipotent char", metadata !3, i64 0}
!3 = metadata !{metadata !"Simple C/C++ TBAA"}
This IR is produced by compiling the following with -ftrapv:
char min; int main() { return min + min; }</pre>
</div>
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