http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47148
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
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CC| |hjl.tools at gmail dot com
--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> 2011-01-01 21:03:08
UTC ---
(In reply to comment #3)
> the caller indeed does the needed promotions, as CALL_EXPR's argument has int
> type rather than unsigned char. But when calling the artificial foo.part.0,
> the
> argument passed to it is unsigned char 255 rather than int 255 and it sets a
> QImode %rdi register to -1 (i.e. 255) instead of setting SImode %rdi register
> to 255, which means it is incorrectly sign extended instead of zero extended.
I proposed to update x86-64 psABI to
---
When a value of type _Bool is returned in a register, bit 0 contains the truth
value and bits 1 to 7 shall be zero. When an argument of type _Bool is passed
in a register or on the stack, bit 0 contains the truth value and bits
1 to 31 shall be
zero.
When a value of type signed/unsigned char or short is returned in a register,
bits 0 to 7 for char and bits 0 to 15 for short contain the value and other
bits are left unspecified. When an argument of signed/unsigned type char or
short is passed in a register or on the stack, it shall be sign/zero extended
to
signed/unsigned int.
---
http://gcc.gnu.org/ml/gcc/2010-12/msg00525.html
