https://gcc.gnu.org/bugzilla/show_bug.cgi?id=12086
Eelis <gcc-bugzilla at contacts dot eelis.net> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |gcc-bugzilla at contacts dot
eelis
| |.net
--- Comment #11 from Eelis <gcc-bugzilla at contacts dot eelis.net> ---
This bug means that for
struct X { char a[8]; };
bool f(X x, X y) { return __builtin_memcmp(x.a, y.a, 8); }
gcc emits:
subq $40, %rsp
.cfi_def_cfa_offset 48
movl $8, %edx
movq %rdi, 16(%rsp)
leaq 16(%rsp), %rdi
movq %rsi, (%rsp)
movq %rsp, %rsi
call memcmp
testl %eax, %eax
setne %al
addq $40, %rsp
.cfi_def_cfa_offset 8
ret
while clang emits:
movq %rdi, -8(%rsp)
movq %rsi, -16(%rsp)
cmpq %rsi, -8(%rsp)
setne %al
retq
(which is still suboptimal due to llvm bug #20673).
