p71924506
/
linux_old1
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

x86,ftrace: Shrink ftrace_regs_caller() by one byte 

'Optimize' ftrace_regs_caller. Instead of comparing against an
immediate, the more natural way to test for zero on x86 is: 'test
%r,%r'.

  48 83 f8 00             cmp    $0x0,%rax
  74 49                   je     226 <ftrace_regs_call+0xa3>

  48 85 c0                test   %rax,%rax
  74 49                   je     225 <ftrace_regs_call+0xa2>

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200416115118.867411350@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2020-04-01 16:51:11 +02:00 committed by Ingo Molnar
parent dc2745b619
commit 9f2dfd61dd
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/x86/kernel/ftrace_64.S
View File

@ -240,8 +240,8 @@ SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL)
* See arch_ftrace_set_direct_caller().
*/
movq ORIG_RAX(%rsp), %rax
cmpq $0, %rax
je 1f
testq %rax, %rax
jz 1f
/* Swap the flags with orig_rax */
movq MCOUNT_REG_SIZE(%rsp), %rdi