| Date | Thu, 16 Apr 2020 13:47:12 +0200 | From | Peter Zijlstra <> | Subject | [PATCH v5 06/17] x86,ftrace: Shrink ftrace_regs_caller() by one byte |
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'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> --- arch/x86/kernel/ftrace_64.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- 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_ * 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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