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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - bx instruction generated with -march=armv4 needs --fix-v4bx with external assembler"
href="https://llvm.org/bugs/show_bug.cgi?id=28952">28952</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>bx instruction generated with -march=armv4 needs --fix-v4bx with external assembler
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.9
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>raj.khem@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>This program below
extern void (*foo_func) ();
void
foo ()
{
(*foo_func) ();
}
when compiled like below using armv4 for march, ends up wit errors when
assembling
"/mnt/oe/openembedded-core/build/tmp-glibc/sysroots/x86_64-linux/usr/bin/arm-oe-linux-gnueabi/arm-oe-linux-gnueabi-as"
-mfloat-abi=softfp -march=armv4 -o a.o /tmp/kraj01/a-0c2038.s
/tmp/kraj01/a-0c2038.s: Assembler messages:
/tmp/kraj01/a-0c2038.s:27: Error: selected processor does not support `bx r0'
in ARM mode
The reason is that when using GNU bintuils we need to pass --fix-v4bx to
assembler and linker when using -march=armv4, to support EABI
here is compile cmd to reproduce it. key options are "-no-integrated-as
-march=armv4 -mfloat-abi=softfp -O2" if I add "-Wa,--fix-v4bx" it works. So
when driver detects that -no-integrated-as + -march-armv4 is used the
--fix-v4bx should be passed unconditionally to assembler
"/mnt/oe/openembedded-core/build/tmp-glibc/sysroots/x86_64-linux/usr/bin/clang-3.9"
-cc1 -triple armv4-oe-linux-gnueabi -S -disable-free -disable-llvm-verifier
-discard-value-names -main-file-name a.c -mrelocation-model static
-mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose
-no-integrated-as -mconstructor-aliases -target-cpu strongarm -target-feature
+soft-float-abi -target-feature +strict-align -target-abi aapcs-linux
-mfloat-abi soft -v -dwarf-column-info -debugger-tuning=gdb -coverage-file
/mnt/oe/openembedded-core/build/tmp-glibc/work/armv5e-oe-linux-gnueabi/gmp/6.1.1-r0/build/mpz/a.c
-resource-dir
/mnt/oe/openembedded-core/build/tmp-glibc/sysroots/x86_64-linux/usr/bin/../lib/clang/3.9.0
-internal-isystem /usr/local/include -internal-isystem
/mnt/oe/openembedded-core/build/tmp-glibc/sysroots/x86_64-linux/usr/bin/../lib/clang/3.9.0/include
-internal-externc-isystem /include -internal-externc-isystem /usr/include -O2
-fno-dwarf-directory-asm -fdebug-compilation-dir
/mnt/oe/openembedded-core/build/tmp-glibc/work/armv5e-oe-linux-gnueabi/gmp/6.1.1-r0/build/mpz
-ferror-limit 19 -fmessage-length 238 -fallow-half-arguments-and-returns
-fno-signed-char -fobjc-runtime=gcc -fdiagnostics-show-option
-fcolor-diagnostics -vectorize-loops -vectorize-slp -o /tmp/kraj01/a-0c2038.s
-x c a.c</pre>
</div>
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