The following commit has been merged into the objtool/core branch of tip: Commit-ID: fdf6101cab968605564f211ab03f396dde67785b Gitweb: https://git.kernel.org/tip/fdf6101cab968605564f211ab03f396dde67785b Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Wed, 01 Apr 2020 16:51:11 +02:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Wed, 22 Apr 2020 23:10:06 +02:00 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@xxxxxxxxxxxxx> Reviewed-by: Miroslav Benes <mbenes@xxxxxxx> Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx> Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200416115118.867411350@xxxxxxxxxxxxx --- arch/x86/kernel/ftrace_64.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index be9aff2..9738ed2 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -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
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