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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - After r315899, .byte directives after x86 prefixes cause errors"
href="https://bugs.llvm.org/show_bug.cgi?id=35749">35749</a>
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<th>Summary</th>
<td>After r315899, .byte directives after x86 prefixes cause errors
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<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>release blocker
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dimitry@andric.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<div>
<pre>Related to <a class="bz_bug_link
bz_status_ASSIGNED "
title="ASSIGNED - After r315899, comments after x86 prefixes cause errors"
href="show_bug.cgi?id=35741">bug 35741</a>, after <a href="https://reviews.llvm.org/rL315899">https://reviews.llvm.org/rL315899</a> (fixing x86
prefix issues related to <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [MC] Disassembler does not support x86 instruction prefixes"
href="show_bug.cgi?id=7709">bug 7709</a>, <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [x86 disassembler] Wrong disassemble for some SSE2 instructions."
href="show_bug.cgi?id=17697">bug 17697</a>, <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [x86 disassembler] prefix ordering may ignore opsize and rep[n]e prefixes"
href="show_bug.cgi?id=19251">bug 19251</a>, <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [x86 disassembler] 'xchg' instruction uses two different sized register operands with data16 prefix"
href="show_bug.cgi?id=32809">bug 32809</a> and bug
21640), .byte directives directly after an x86 instruction prefix are no longer
accepted.
For example:
rep
.byte 0xa4 # movsb
This is accepted by both clang before r315899 and GNU as, but clang r315899
gives:
rep-byte.s:1:1: error: invalid instruction mnemonic '.byte'
rep
^~~
Note that this construct is used to put rep prefixes on instructions that might
not be known by the assembler yet, such as VIA C3 "xcrypt-cbc" instructions
[1]:
/* The .byte line is really VIA C3 "xcrypt-cbc" instruction */
__asm __volatile(
"pushf \n\t"
"popf \n\t"
"rep \n\t"
".byte 0x0f, 0xa7, 0xd0"
: "+a" (iv), "+c" (count), "+D" (out), "+S" (in)
: "b" (key), "d" (cw)
: "cc", "memory"
);
[1]
<a href="https://github.com/freebsd/freebsd/blob/master/sys/crypto/via/padlock_cipher.c#L92">https://github.com/freebsd/freebsd/blob/master/sys/crypto/via/padlock_cipher.c#L92</a></pre>
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