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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [arm][thumb2][integrated as] incorrect padding at end of code sequence"
href="https://bugs.llvm.org/show_bug.cgi?id=51929">51929</a>
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<th>Summary</th>
<td>[arm][thumb2][integrated as] incorrect padding at end of code sequence
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: ARM
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>ndesaulniers@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>kristof.beyls@arm.com, llvm-bugs@lists.llvm.org, natechancellor@gmail.com, rengolin@gmail.com, smithp352@googlemail.com, srhines@google.com, Ties.Stuij@arm.com
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<th>Blocks</th>
<td>4068
</td>
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<p>
<div>
<pre>Via: <a href="https://github.com/ClangBuiltLinux/linux/issues/1447">https://github.com/ClangBuiltLinux/linux/issues/1447</a>
$ clang --target=arm-linux-gnueabi -Wa,-mthumb tlb-v7.s -o clang.o
-Wa,-march=armv7-a -c
and
$ clang --target=arm-linux-gnueabi -Wa,-mthumb tlb-v7.s -o gas.o
-Wa,-march=armv7-a -c -fno-integrated-as
produce different output given the input:
.align 0
mov pc, lr
ie.
$ llvm-objdump -dr clang.o | tail -n2
00000000 <$t.0>:
0: f7 46 mov pc, lr
$ llvm-objdump -dr gas.o | tail -n3
00000000 <$t>:
0: f7 46 mov pc, lr
2: 00 bf nop
This looks somewhat related perhaps to
<a class="bz_bug_link
bz_status_NEW "
title="NEW - [arm assembler]: Incorrect alignment NOPs in mixed ARM and Thumb assembly"
href="show_bug.cgi?id=48512">https://bugs.llvm.org/show_bug.cgi?id=48512</a>. Looking throught GAS' issue
tracker, I think this might be the equivalent bug.
<a href="https://sourceware.org/bugzilla/show_bug.cgi?id=12931">https://sourceware.org/bugzilla/show_bug.cgi?id=12931</a>
This difference in behavior seems to be causing a boot failure for THUMB2 linux
kernels assembled with Clang in QEMU 6.2.0+.</pre>
</div>
</p>
<div id="referenced">
<hr style="border: 1px dashed #969696">
<b>Referenced Bugs:</b>
<ul>
<li>
[<a class="bz_bug_link
bz_status_CONFIRMED "
title="CONFIRMED - [Meta] Compiling the Linux kernel with clang"
href="https://bugs.llvm.org/show_bug.cgi?id=4068">Bug 4068</a>] [Meta] Compiling the Linux kernel with clang
</li>
</ul>
</div>
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