Hi there,
Can anyone explain why has been chosen that -march=i686 makes the
compiler change the normal behaviour, and zero-expand unsigned short
parameters into 32-bit registers by all means?
E.g.
void __attribute(( regparm(2) )) myoutl( d, p )
{
asm(" outl %0,(%w1) \n"
:
: "a" (d), "d" (p) );
}
assembled with
gcc -Os -fomit-frame-pointer -march=i586 ...
gives us
outl %eax,(%dx)
ret
but changing "-march=i686" gives us
movzwl %dx,%edx
outl %eax,(%dx)
ret
Is it a bug, or had any developer a good reason to do so?
David
