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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - -mfpu=neon overrides +crypto part of -march=armv8-a+crypto"
href="https://bugs.llvm.org/show_bug.cgi?id=38629">38629</a>
</td>
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<th>Summary</th>
<td>-mfpu=neon overrides +crypto part of -march=armv8-a+crypto
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>7.0
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Driver
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>lennox@cs.columbia.edu
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Passing -mfpu=neon on the clang command line for arm32 (specifically with the
target triple armv7-none-linux-androideabi) disables the __ARM_FEATURE_CRYPTO
feature which would normally be enabled by -march=armv8+crypto, even though the
armv8 part of the flag takes effect, even if the -march flag is specified
later.
This is particularly problematic because -mfpu=neon tends to get added
automatically by Android build procedures when vector support is needed.
E.g.:
$ clang -target armv7-none-linux-androideabi -mfloat-abi=softfp -E -dM -x c
/dev/null | egrep 'CRYPTO|ARM_ARCH '
#define __ARM_ARCH 7
$ clang -target armv7-none-linux-androideabi -mfloat-abi=softfp
-march=armv8+crypto -E -dM -x c /dev/null | egrep 'CRYPTO|ARM_ARCH '
#define __ARM_ARCH 8
#define __ARM_FEATURE_CRYPTO 1
$ clang -target armv7-none-linux-androideabi -mfloat-abi=softfp -mfpu=neon
-march=armv8+crypto -E -dM -x c /dev/null | egrep 'CRYPTO|ARM_ARCH '
#define __ARM_ARCH 8
$ clang -target armv7-none-linux-androideabi -v
Android (4751641 based on r328903) clang version 7.0.2
(<a href="https://android.googlesource.com/toolchain/clang">https://android.googlesource.com/toolchain/clang</a>
003100370607242ddd5815e4a043907ea9004281)
(<a href="https://android.googlesource.com/toolchain/llvm">https://android.googlesource.com/toolchain/llvm</a>
1d739ffb0366421d383e04ff80ec2ee591315116) (based on LLVM 7.0.2svn)
Target: armv7-none-linux-android
Thread model: posix
InstalledDir:
/Users/jonathan/Android/android-ndk-r18-beta1/toolchains/llvm/prebuilt/darwin-x86_64/bin</pre>
</div>
</p>
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