https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867
--- Comment #3 from Sebastian Huber <sebastian.hu...@embedded-brains.de> ---
clang 3.7 generates optimal code on x86 in both cases:
.text
.file "test.c"
.globl f
.align 16, 0x90
.type f,@function
f: # @f
.cfi_startproc
# BB#0:
movl $1, %ecx
xorl %eax, %eax
lock cmpxchgl %ecx, (%rdi)
retq
.Lfunc_end0:
.size f, .Lfunc_end0-f
.cfi_endproc
.globl g
.align 16, 0x90
.type g,@function
g: # @g
.cfi_startproc
# BB#0:
movl $1, %ecx
xorl %eax, %eax
lock cmpxchgl %ecx, (%rdi)
retq
.Lfunc_end1:
.size g, .Lfunc_end1-g
.cfi_endproc
.ident "clang version 3.7.0 (tags/RELEASE_370/final)"
.section ".note.GNU-stack","",@progbits
