https://gcc.gnu.org/bugzilla/show_bug.cgi?id=28306
Steven Bosscher <steven at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2006-07-07 17:30:13 |2019-3-5
Host|i686-pc-linux-gnu |
--- Comment #4 from Steven Bosscher <steven at gcc dot gnu.org> ---
GCC trunk today on x86-64 produces:
gen_x86_64_shrd(int):
xorl %eax, %eax
ret
ok(int):
movl $1, %eax
ret
ix86_split_ashr(int):
testl %edi, %edi
movl $ok(int), %eax
movl $gen_x86_64_shrd(int), %edx
cmove %rdx, %rax
xorl %edi, %edi
jmp *%rax
FWIW clang trunk also does not optimize this, yielding:
ix86_split_ashr(int): # @ix86_split_ashr(int)
testl %edi, %edi
movl $gen_x86_64_shrd(int), %eax
movl $ok(int), %ecx
cmoveq %rax, %rcx
xorl %edi, %edi
jmpq *%rcx # TAILCALL
ok(int): # @ok(int)
movl $1, %eax
retq
gen_x86_64_shrd(int): # @gen_x86_64_shrd(int)
xorl %eax, %eax
retq
ICC 19.0.1 _does_ optimize, resulting in:
ix86_split_ashr(int):
ret #24.1
_INTERNALf242c0c5::gen_x86_64_shrd(int):
xorl %eax, %eax #6.10
ret #6.10
_INTERNALf242c0c5::ok(int):
movl $1, %eax #12.10
ret #12.10
