Mercurial > hg > nginx
diff src/os/unix/ngx_gcc_atomic_amd64.h @ 1009:ee5f21acea76
optimization
author | Igor Sysoev <igor@sysoev.ru> |
---|---|
date | Thu, 11 Jan 2007 16:07:38 +0000 |
parents | f1ebccfd95f9 |
children | d620f497c50f |
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--- a/src/os/unix/ngx_gcc_atomic_amd64.h +++ b/src/os/unix/ngx_gcc_atomic_amd64.h @@ -24,8 +24,11 @@ * * * The "r" is any register, %rax (%r0) - %r16. - * The "=a" and "a" are the %rax register. Although we can return result - * in any register, we use %rax because it is used in cmpxchgq anyway. + * The "=a" and "a" are the %rax register. + * Although we can return result in any register, we use "a" because it is + * used in cmpxchgq anyway. The result is actually in %al but not in $rax, + * however as the code is inlined gcc can test %al as well as %rax. + * * The "cc" means that flags were changed. */ @@ -33,14 +36,13 @@ static ngx_inline ngx_atomic_uint_t ngx_atomic_cmp_set(ngx_atomic_t *lock, ngx_atomic_uint_t old, ngx_atomic_uint_t set) { - ngx_atomic_uint_t res; + u_char res; __asm__ volatile ( NGX_SMP_LOCK " cmpxchgq %3, %1; " - " setz %b0; " - " movzbq %b0, %0; " + " sete %0; " : "=a" (res) : "m" (*lock), "a" (old), "r" (set) : "cc", "memory");