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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - llvm generates invalid mov command for arm7tdmi target"
href="http://llvm.org/bugs/show_bug.cgi?id=16855">16855</a>
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<th>Summary</th>
<td>llvm generates invalid mov command for arm7tdmi target
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>3.3
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>LLVM Codegen
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>sven.koehler@gmail.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>Command:
clang -target arm-softfloat-eabi -mcpu=arm7tdmi -mthumb -O2 -c -o foo.o foo.c
Contents of foo.c:
int foo(int a, int b) { return b; }
Generated assembler code (relevant part):
foo:
mov r0, r1
bx lr
Actual Result:
/tmp/foo-Kf30BB.s: Assembler messages:
/tmp/foo-Kf30BB.s:16: Error: MOV Rd, Rs with two low registers is not permitted
on this architecture -- `mov r0,r1'
clang: error: assembler (via gcc) command failed with exit code 1 (use -v to
see invocation)
Expected Result:
clang/llvm should use movs instead of mov. According to offical arm documents,
mov with two low register is not possible in thumb mode in architectures before
ARMv6. See
<a href="http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0489i/Cihedhif.html">http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0489i/Cihedhif.html</a>
The drawback of movs is, that is resets some flags and stuff. I omit the
details of my arm-softfloat-eabi gcc/binutils toolchain since the error
detected by the assembler seems to be quite correct.</pre>
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