<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - -globals-aa affected by dbg intrinsic leading to different code after instcombine"
href="https://bugs.llvm.org/show_bug.cgi?id=35899">35899</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>-globals-aa affected by dbg intrinsic leading to different code after instcombine
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>mikael.holmen@ericsson.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=19650" name="attach_19650" title="reproducer">attachment 19650</a> <a href="attachment.cgi?id=19650&action=edit" title="reproducer">[details]</a></span>
reproducer
opt -S -o - foo.ll -globals-aa -instcombine
and
opt -S -o - foo.ll -strip-debug -globals-aa -instcombine
yields different results on the attached foo.ll.
We get
define void @foo() {
store i8 42, i8* @g, align 1
call void @bar(i8 1)
%_tmp = load i8, i8* @g, align 1
call void @gaz(i8 %_tmp)
ret void
}
and
define void @foo() {
store i8 42, i8* @g, align 1
call void @bar(i8 1)
call void @gaz(i8 42)
ret void
}
It seems like the
call void @llvm.dbg.value(metadata i64 0, metadata !6, metadata
!DIExpression()), !dbg !13
in
define void @bar(i8 %p) {
call void @llvm.dbg.value(metadata i64 0, metadata !6, metadata
!DIExpression()), !dbg !13
ret void
}
disturbs -globals-aa then leading to instcombine not doing the optimization.
I don't know -globals-aa at all, but I examined what happened in
GlobalsModRef.cpp a little bit and I found that if I do
- if (isAllocationFn(&I, &TLI) || isFreeCall(&I, &TLI)) {
+ if (isa<DbgInfoIntrinsic>(I))
+ continue;
+ else if (isAllocationFn(&I, &TLI) || isFreeCall(&I, &TLI)) {
in GlobalsAAResult::AnalyzeCallGraph around line 578 then I don't get the
difference anymore. I've no idea if that's a sane fix or not though.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>