https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92821
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |hjl.tools at gmail dot com,
| |hubicka at gcc dot gnu.org,
| |matz at gcc dot gnu.org
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I believe it is a LLVM bug.
At least, reading
https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-1.0.pdf, I can't find
in the Parameter Passing section anything that would say that arguments smaller
than 64-bit are passed sign or zero extended to 64-bit like some other psABIs
require. The only related thing is
"When a value of type _Bool is returned or passed in a register or on the
stack,
bit 0 contains the truth value and bits 1 to 7 shall be zero."
with a footnote:
"Other bits are left unspecified, hence the consumer side of those values can
rely on it being 0 or 1 when truncated to 8 bit."
which says that _Bool has only significant low 8 bits and the rest is
unspecified.
