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Subject[PATCH] x86-64: adjust ia32entry branches for better static prediction
Swap branch pairs so that the static branch prediction logic would
consider the syscall-number-in-range case the taken path.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

---
arch/x86/ia32/ia32entry.S | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

--- linux-2.6.32-rc5/arch/x86/ia32/ia32entry.S 2009-10-19 13:12:43.000000000 +0200
+++ 2.6.32-rc5-x86_64-ia32-syscall-trace-branch-dir/arch/x86/ia32/ia32entry.S 2009-10-19 09:36:39.000000000 +0200
@@ -249,9 +249,9 @@ sysenter_tracesys:
call syscall_trace_enter
LOAD_ARGS32 ARGOFFSET /* reload args from stack in case ptrace changed it */
RESTORE_REST
- cmpl $(IA32_NR_syscalls-1),%eax
- ja int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */
- jmp sysenter_do_call
+ cmpl $IA32_NR_syscalls,%eax
+ jb sysenter_do_call
+ jmp int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */
CFI_ENDPROC
ENDPROC(ia32_sysenter_target)

@@ -368,9 +368,9 @@ cstar_tracesys:
LOAD_ARGS32 ARGOFFSET, 1 /* reload args from stack in case ptrace changed it */
RESTORE_REST
xchgl %ebp,%r9d
- cmpl $(IA32_NR_syscalls-1),%eax
- ja int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */
- jmp cstar_do_call
+ cmpl $IA32_NR_syscalls,%eax
+ jb cstar_do_call
+ jmp int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */
END(ia32_cstar_target)

ia32_badarg:
@@ -445,9 +445,9 @@ ia32_tracesys:
call syscall_trace_enter
LOAD_ARGS32 ARGOFFSET /* reload args from stack in case ptrace changed it */
RESTORE_REST
- cmpl $(IA32_NR_syscalls-1),%eax
- ja int_ret_from_sys_call /* ia32_tracesys has set RAX(%rsp) */
- jmp ia32_do_call
+ cmpl $IA32_NR_syscalls,%eax
+ jb ia32_do_call
+ jmp int_ret_from_sys_call /* ia32_tracesys has set RAX(%rsp) */
END(ia32_syscall)

ia32_badsys:




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