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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - BMI intrinsic not recognized?"
href="http://llvm.org/bugs/show_bug.cgi?id=19431">19431</a>
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<th>Summary</th>
<td>BMI intrinsic not recognized?
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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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>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Headers
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
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<th>Reporter</th>
<td>sanjay3.0.0.0@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>Using:
$ ./clang -v
clang version 3.5.0 (trunk 206222) (llvm/trunk 206220)
Target: x86_64-apple-darwin13.1.0
Thread model: posix
I tried to generate an x86 bit manipulation instruction (BMI) via its C
intrinsic:
$ cat bmi.c
#include <x86intrin.h>
int foo(int a) { return _blsmsk_u32(a); }
$ ./clang bmi.c -mbmi -S -o -
bmi.c:2:25: warning: implicit declaration of function '_blsmsk_u32' is invalid
in C99 [-Wimplicit-function-declaration]
The generated asm shows:
callq __blsmsk_u32
I confirmed the same behavior with clang 3.2 on Ubuntu 13.04. However, gcc
4.8.2 generates the expected instruction from the same source file and compiler
flags:
blsmsk %edi, %eax
I also confirmed that a BMI2 instruction is generated using the same kind of C
instrinsic (I tested '_bzhi_u32') and "-mbmi2" with both clang versions and
gcc.
Is "-mbmi" no longer the correct feature flag for the BMI ISA?</pre>
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