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patch from njk: make x86_64 __uniclone branchless.

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This commit is contained in:
Rich Felker 2011-02-16 09:49:54 -05:00
parent bad481266e
commit 22cd9cae81
1 changed files with 6 additions and 6 deletions
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12
src/thread/x86_64/clone.s
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@ -4,6 +4,7 @@
.type __uniclone,%function
/* rdi = child_stack, rsi = start, rdx = pthread_struct */
__uniclone:
subq $8,%rsp /* pad parent stack to prevent branch later */
subq $16,%rdi /* grow child_stack */
mov %rsi,8(%rdi) /* push start onto child_stack as return ptr */
mov %rdx,0(%rdi) /* push pthread_struct onto child_stack */
@ -13,10 +14,9 @@ __uniclone:
movl $56,%eax /* clone syscall number */
movl $0x7d0f00,%edi /* rdi = flags */
mov %r10,%rdx /* rdx = parent_id */
syscall /* clone(flags, child_stack, parent_id,
* child_id, tls) */
test %rax,%rax
jnz 1f /* if we're in the parent -> goto 1f */
pop %rdi /* restore pthread_struct from child stack */
1: ret
syscall /* clone(flags, child_stack, parent_id,
* child_id, tls) */
pop %rdi /* child stack: restore pthread_struct
* parent stack: undo rsp displacement */
ret
.size __uniclone,.-__uniclone