Mini Shell
/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#if (NGX_SMP)
#define NGX_SMP_LOCK "lock;"
#else
#define NGX_SMP_LOCK
#endif
/*
* "cmpxchgl r, [m]":
*
* if (eax == [m]) {
* zf = 1;
* [m] = r;
* } else {
* zf = 0;
* eax = [m];
* }
*
*
* The "r" means the general register.
* The "=a" and "a" are the %eax register.
* Although we can return result in any register, we use "a" because it is
* used in cmpxchgl anyway. The result is actually in %al but not in %eax,
* however, as the code is inlined gcc can test %al as well as %eax,
* and icc adds "movzbl %al, %eax" by itself.
*
* The "cc" means that flags were changed.
*/
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)
{
u_char res;
__asm__ volatile (
NGX_SMP_LOCK
" cmpxchgl %3, %1; "
" sete %0; "
: "=a" (res) : "m" (*lock), "a" (old), "r" (set) : "cc", "memory");
return res;
}
/*
* "xaddl r, [m]":
*
* temp = [m];
* [m] += r;
* r = temp;
*
*
* The "+r" means the general register.
* The "cc" means that flags were changed.
*/
#if !(( __GNUC__ == 2 && __GNUC_MINOR__ <= 7 ) || ( __INTEL_COMPILER >= 800 ))
/*
* icc 8.1 and 9.0 compile broken code with -march=pentium4 option:
* ngx_atomic_fetch_add() always return the input "add" value,
* so we use the gcc 2.7 version.
*
* icc 8.1 and 9.0 with -march=pentiumpro option or icc 7.1 compile
* correct code.
*/
static ngx_inline ngx_atomic_int_t
ngx_atomic_fetch_add(ngx_atomic_t *value, ngx_atomic_int_t add)
{
__asm__ volatile (
NGX_SMP_LOCK
" xaddl %0, %1; "
: "+r" (add) : "m" (*value) : "cc", "memory");
return add;
}
#else
/*
* gcc 2.7 does not support "+r", so we have to use the fixed
* %eax ("=a" and "a") and this adds two superfluous instructions in the end
* of code, something like this: "mov %eax, %edx / mov %edx, %eax".
*/
static ngx_inline ngx_atomic_int_t
ngx_atomic_fetch_add(ngx_atomic_t *value, ngx_atomic_int_t add)
{
ngx_atomic_uint_t old;
__asm__ volatile (
NGX_SMP_LOCK
" xaddl %2, %1; "
: "=a" (old) : "m" (*value), "a" (add) : "cc", "memory");
return old;
}
#endif
/*
* on x86 the write operations go in a program order, so we need only
* to disable the gcc reorder optimizations
*/
#define ngx_memory_barrier() __asm__ volatile ("" ::: "memory")
/* old "as" does not support "pause" opcode */
#define ngx_cpu_pause() __asm__ (".byte 0xf3, 0x90")
Zerion Mini Shell 1.0