https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92985
Avi Kivity <a...@cloudius-systems.com> changed:
What |Removed |Added
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CC| |a...@cloudius-systems.com
--- Comment #5 from Avi Kivity <a...@cloudius-systems.com> ---
Here's another example:
#include <compare>
int strong_ordering_to_int(std::strong_ordering x) {
if (x == std::strong_ordering::equal) {
return 0;
} else if (x == std::strong_ordering::less) {
return -1;
} else if (x == std::strong_ordering::greater) {
return 1;
}
__builtin_unreachable();
}
Used to translate the new std::strong_ordering back to int (in this case for
compatibility with older code, but one can imagine many such translations from
opaque enums to another enum when crossing an API boundary).
gcc generates (-O3)
strong_ordering_to_int(std::strong_ordering):
xorl %eax, %eax
testb %dil, %dil
je .L1
xorl %eax, %eax
cmpb $-1, %dil
setne %al
leal -1(%rax,%rax), %eax
.L1:
ret
Where it could have generated
movsx %dil, %eax
ret
