https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116245
--- Comment #3 from Stefan Schulze Frielinghaus <stefansf at gcc dot gnu.org>
---
Thanks for the ping. The test is skipped for -m31 and fails for -m64. Maybe
this is some sort of endianness thingy?
typedef __attribute__((__vector_size__ (64))) unsigned __int128 VV;
__attribute__ ((noipa))
unsigned char
foo (VV vv)
{
return ((VC) vv)[0];
}
int
main (void)
{
unsigned char x = foo ((VV) { -0xff });
__builtin_printf ("%u\n", x);
}
prints 255 on s390 and 1 on x86_64. At start of function foo we have
(gdb) x/16xb $r2
0x3ffffff9450: 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff
0x3ffffff9458: 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0x01
In foo we then load the most significant byte:
<foo> llgc %r2,0(%r2)
<foo+6> br %r14
and zero extend it.
