https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78794
--- Comment #9 from Yuri Rumyantsev <ysrumyan at gmail dot com> ---
Hi Uros,
I checked thta with your patch performance is recovered on Avoton machine:
before after
462.libquantum 18.4000 20.9000 +13.58%
Best regards.
Yuri.
2016-12-13 17:54 GMT+03:00 ubizjak at gmail dot com <gcc-bugzi...@gcc.gnu.org>:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78794
>
> --- Comment #8 from Uroš Bizjak <ubizjak at gmail dot com> ---
> (In reply to Uroš Bizjak from comment #7)
>
>> Yes, this is a good idea.
> Also, since pandn on non-BMI target replaces four arith insns with one, the
> gain should be raised for 2 * ix86_cost->add for a total of 3 *
> ix86_cost->add.
>
> The final patch is thus:
>
> --cut here--
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 1cd1cd8..6a746b2 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -3417,7 +3417,11 @@ dimode_scalar_chain::compute_convert_gain ()
> || GET_CODE (src) == AND)
> {
> gain += ix86_cost->add;
> - if (CONST_INT_P (XEXP (src, 0)))
> + /* Additional gain for andnot for targets without BMI. */
> + if (GET_CODE (XEXP (src, 0)) == NOT
> + && !TARGET_BMI)
> + gain += 2 * ix86_cost->add;
> + else if (CONST_INT_P (XEXP (src, 0)))
> gain -= vector_const_cost (XEXP (src, 0));
> if (CONST_INT_P (XEXP (src, 1)))
> gain -= vector_const_cost (XEXP (src, 1));
> --cut here-
>
> Please also note that on BMI targets, the attached testcase won't be
> converted,
> which is a good thing - the loop on BMI targets looks like:
>
> .L4:
> movl 4(%eax), %edi
> andn 4(%esp), %edi, %ebx
> movl (%eax), %esi
> movl %ebx, %ebp
> andn (%esp), %esi, %ecx
> orl %ecx, %ebp
> jne .L3
> xorl 8(%esp), %esi
> xorl 12(%esp), %edi
> movl %esi, (%eax)
> movl %edi, 4(%eax)
> .L3:
> addl $12, %eax
> cmpl %edx, %eax
> jne .L4
>
> --
> You are receiving this mail because:
> You reported the bug.
