#112 Assembler error on arm at -O0 (fastlock.h)

[Julien BLACHE]

OpenSER (1.1.0, but probably applies to all versions)
fails to build on arm at -O0, spitting out an assembler
error:

$ gcc -c -fPIC -g -O0 -g tree234.i
/tmp/cco6vA7j.s: Assembler messages:
/tmp/cco6vA7j.s:172: Error: Rn must not overlap other
operands -- `swpb r3,r2,[r3]'

The code at fault is the inline assembly in fastlock.h:

asm volatile(

"# here \n\t"

"swpb %0, %1, [%2] \n\t"

"=r" (val)

"r"(1), "r" (lock) : "memory"
);

See the Debian bug report:
<http://bugs.debian.org/393858>

And the GCC PR:
<http://gcc.gnu.org/PR29329>

The problem in the GCC PR is not caused by this
problem, it's a bug in the optimizer on arm, but this
issue came up while investigating this PR.

Thanks,

JB.

[Julien BLACHE]

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Hi,

The attached one-liner fixes the problem.

JB.

[Julien BLACHE]

inline asm constraint fix for fastlock.h on arm

[Bogdan-Andrei Iancu]

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Hi Julien,

thanks for the patch - I applied on cvs for both head and
1.1.0 (last stable) versions.

regards,
bogdan