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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - x86 FMA not generated unless fast-math is used?"
href="http://llvm.org/bugs/show_bug.cgi?id=17188">17188</a>
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<th>Summary</th>
<td>x86 FMA not generated unless fast-math is used?
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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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>
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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>
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<th>Reporter</th>
<td>kkhoo@perfwizard.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>I was expecting a target that has the FMA feature to use FMA instructions with
-O3 (or even less), but:
$ ./clang -v
clang version 3.4 (trunk 189776)
Target: x86_64-apple-darwin11.4.2
Thread model: posix
$ cat fma.c
double foo(double x) {
return x*x + x;
}
$ ./clang -S -O3 -fomit-frame-pointer -march=core-avx2 -o /dev/stdout fma.c
.section __TEXT,__text,regular,pure_instructions
.globl _foo
.align 4, 0x90
_foo: ## @foo
.cfi_startproc
## BB#0: ## %entry
vmulsd %xmm0, %xmm0, %xmm1
vaddsd %xmm0, %xmm1, %xmm0
ret</pre>
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