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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Codegen being moved outside of volatile block"
href="https://bugs.llvm.org/show_bug.cgi?id=45149">45149</a>
</td>
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<tr>
<th>Summary</th>
<td>Codegen being moved outside of volatile block
</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>Windows NT
</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>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>andrea.dibiagio@gmail.com, craig.topper@gmail.com, greg.bedwell@sony.com, llvm-bugs@lists.llvm.org, matze@braunis.de, spatel+llvm@rotateright.com
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<p>
<div>
<pre><a href="https://godbolt.org/z/bo6w2F">https://godbolt.org/z/bo6w2F</a>
#include <x86intrin.h>
__v16qi foo(__v16qi a, __v16qi b) {
__asm volatile("# LLVM-MCA-BEGIN foo");
__v16qi result = a + b;
__asm volatile("# LLVM-MCA-END foo");
return result;
}
I'm seeing an issue where depending on the target cpu the generated asm is
getting moved out of the volatile comment block.
clang -g0 -O3:
# %bb.0:
#APP
# LLVM-MCA-BEGIN foo
#NO_APP
paddb %xmm1, %xmm0
#APP
# LLVM-MCA-END foo
#NO_APP
retq
clang -g0 -O3 -march=sandybridge:
# %bb.0:
#APP
# LLVM-MCA-BEGIN foo
#NO_APP
vpaddb %xmm0, %xmm1, %xmm0
#APP
# LLVM-MCA-END foo
#NO_APP
retq
clang -g0 -O3 -march=btver2:
# %bb.0:
vpaddb %xmm0, %xmm1, %xmm0
#APP
# LLVM-MCA-BEGIN foo
#NO_APP
#APP
# LLVM-MCA-END foo
#NO_APP
retq
which prevents llvm-mca from reporting on the code snippet.</pre>
</div>
</p>
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