https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95737
Jens Seifert <jens.seifert at de dot ibm.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |UNCONFIRMED
Resolution|DUPLICATE |---
--- Comment #3 from Jens Seifert <jens.seifert at de dot ibm.com> ---
This is different as the extsw also happens if the result gets used e.g.
followed by a andc, which is my case. I obviously oversimplified the sample. It
has nothing to do with function result and ABI requirements. gcc assume that
the result of -(a < b) implemented by subfc, subfe is signed 32-bit. But the
result is already 64-bit.
unsigned long long branchlesconditional(unsigned long long a, unsigned long
long b, unsigned long long c)
{
unsigned long long mask = -(a < b);
return c &~ mask;
}
results in
_Z20branchlesconditionalyyy:
.LFB1:
.cfi_startproc
subfc 4,4,3
subfe 3,3,3
not 3,3
extsw 3,3
and 3,3,5
blr
expected
subfc
subfe
andc
