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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Emit cmpxchg16b loops for i128 atomicrmw instructions when mattr=+cx16"
href="http://llvm.org/bugs/show_bug.cgi?id=17611">17611</a>
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<th>Summary</th>
<td>Emit cmpxchg16b loops for i128 atomicrmw instructions when mattr=+cx16
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>david.majnemer@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>consider:
define void @test(i128* %a) nounwind {
entry:
%0 = cmpxchg i128* %a, i128 1, i128 1 seq_cst
%1 = atomicrmw xchg i128* %a, i128 1 seq_cst
%2 = atomicrmw add i128* %a, i128 1 seq_cst
%3 = atomicrmw sub i128* %a, i128 1 seq_cst
%4 = atomicrmw and i128* %a, i128 1 seq_cst
%5 = atomicrmw nand i128* %a, i128 1 seq_cst
%6 = atomicrmw or i128* %a, i128 1 seq_cst
%7 = atomicrmw xor i128* %a, i128 1 seq_cst
ret void
}
compile with:
~/llvm/build/bin/llc /var/tmp/PR17481.ll -o - -mattr=+cx16 -march=x86-64
-mcpu=corei7
note that we are emitting libcalls for atomicrmw instructions instead of doing
something like:
.L6:
movq %rax, %rbx
movq %rdx, %rcx
orq $1, %rbx
lock cmpxchg16b -16(%rsp)
jne .L6</pre>
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