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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - ARM miscompilation of store of global alias"
href="https://llvm.org/bugs/show_bug.cgi?id=31896">31896</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>ARM miscompilation of store of global alias
</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>
<tr>
<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>
<tr>
<th>Component</th>
<td>Backend: ARM
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>eugeni.stepanov@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>$ cat q.ll
target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
target triple = "thumbv7--linux"
@X = constant {i8, i8 } { i8 0, i8 0 }
@XA = alias i8, getelementptr inbounds ({ i8, i8 }, {i8, i8}* @X, i32 0, i32 0)
@XB = alias i8, getelementptr inbounds ({ i8, i8 }, {i8, i8}* @X, i32 0, i32 1)
; not using alias - OK
define void @zzz(i8** %p) align 2 {
entry:
store i8* getelementptr inbounds ({ i8, i8 }, {i8, i8}* @X, i32 0, i32 1), i8
**%p, align 4
ret void
}
; store by alias. zzzA and zzzB generate identical code.
define void @zzzA(i8** %p) align 2 {
entry:
store i8* @XA, i8 **%p, align 4
ret void
}
define void @zzzB(i8** %p) align 2 {
entry:
store i8* @XB, i8 **%p, align 4
ret void
}
$ bin/llc q.ll -o -
zzz:
.fnstart
@ BB#0: @ %entry
movw r1, :lower16:X
movt r1, :upper16:X
adds r1, #1
str r1, [r0]
bx lr
zzzA:
.fnstart
@ BB#0: @ %entry
movw r1, :lower16:X
movt r1, :upper16:X
str r1, [r0]
bx lr
zzzB:
.fnstart
@ BB#0: @ %entry
movw r1, :lower16:X
movt r1, :upper16:X
str r1, [r0]
bx lr
Note how @XA and @XB are different, but assembly for @zzzA and @zzzB is the
same.</pre>
</div>
</p>
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