On Tue, Jan 17, 2017 at 04:03:08PM +0300, Andrew Senkevich wrote:
> > I've played a bit w/ SDE. And looks like operands are not early clobber:
> > TID0: INS 0x00000000004003ee AVX512VEX kmovd k0, eax
> > TID0: k0 := 00000000_ffffffff
> > ...
> > TID0: INS 0x00000000004003f4 AVX512VEX kshiftlw k0, k0, 0x3
> > TID0: k0 := 00000000_0000fff8
> >
> > You can see that same dest and source works just fine.
>
> Hmm, I looked only on what ICC generates, and it was not correct way.
I've just tried
int
main ()
{
unsigned int a = 0x5555;
asm volatile ("kmovw %1, %%k6; kshiftlw $1, %%k6, %%k6; kmovw %%k6, %0" :
"=r" (a) : "r" (a) : "k6");
__builtin_printf ("%x\n", a);
return 0;
}
on KNL and got 0xaaaa.
Are you going to report to the SDM authors so that they fix it up?
E.g. using TEMP <- SRC1[0:...] before DEST[...] <- 0 and using TEMP
instead of SRC1[0:...] would fix it, or filling up TEMP first and only
at the end assigning DEST <- TEMP etc. would do.
Jakub
