path: root/arch/i386/atomic.h
diff options
authorRich Felker <>2015-09-09 07:18:28 +0000
committerRich Felker <>2015-09-09 07:18:28 +0000
commit878887c50cccd45b5cabe6ed2ac743941f3417ea (patch)
tree29adc470d9da67b9a6ab051a2be656a54d3c524e /arch/i386/atomic.h
parentdeb85ab44dbe784ba6174b8cf376d35aeacbe309 (diff)
fix missing earlyclobber flag in i386 a_ctz_64 asm
this error was only found by reading the code, but it seems to have been causing gcc to produce wrong code in malloc: the same register was used for the output and the high word of the input. in principle this could have caused an infinite loop searching for an available bin, but in practice most x86 models seem to implement the "undefined" result of the bsf instruction as "unchanged".
Diffstat (limited to 'arch/i386/atomic.h')
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/i386/atomic.h b/arch/i386/atomic.h
index 25441df2..fd222eae 100644
--- a/arch/i386/atomic.h
+++ b/arch/i386/atomic.h
@@ -7,7 +7,7 @@ static inline int a_ctz_64(uint64_t x)
int r;
__asm__( "bsf %1,%0 ; jnz 1f ; bsf %2,%0 ; addl $32,%0\n1:"
- : "=r"(r) : "r"((unsigned)x), "r"((unsigned)(x>>32)) );
+ : "=&r"(r) : "r"((unsigned)x), "r"((unsigned)(x>>32)) );
return r;