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Re: [PATCH, i386, AVX] Fix typo in i386.c/standard_sse_constant_opcode ().
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Kirill Yukhin <kirill dot yukhin at gmail dot com>
- Cc: Richard Biener <rguenther at suse dot de>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Uros Bizjak <ubizjak at gmail dot com>
- Date: Wed, 23 Mar 2016 12:55:48 +0100
- Subject: Re: [PATCH, i386, AVX] Fix typo in i386.c/standard_sse_constant_opcode ().
- Authentication-results: sourceware.org; auth=none
- References: <20160323112150 dot GA59478 at msticlxl57 dot ims dot intel dot com> <20160323114111 dot GW3017 at tucnak dot redhat dot com> <20160323114753 dot GC59478 at msticlxl57 dot ims dot intel dot com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Wed, Mar 23, 2016 at 02:47:54PM +0300, Kirill Yukhin wrote:
> > This code is only executed if standard_sse_constant_p returns 2, which
> > is for 16-byte vectors and all ones for TARGET_SSE2, and for
> > 32-byte vectors for TARGET_AVX2.
> > Thus, IMNSHO the patch is wrong, even for plain -mavx -mno-avx2
> > we want to emit vpcmpeqd %xmm?, %xmm?, %xmm?, so that we don't mix
> > VEX with non-VEX encoded insns.
> You're right. I've updated the patch to check mode size as well.
That is also wrong, you will then emit vpcmpeqd even for -msse2 -mno-avx.
There is really nothing wrong in what is on the trunk, no reason to patch
anything. What the trunk does is, if you have AVX, you emit VEX encoded
insn, if you don't have AVX, you emit normally encoded insn.
And whether there is support to get cheap all ones is the business of
standard_sse_constant_p function, which DTRT.
> commit ae82089e3a4244d870737a7022e66e87042da811
> Author: Kirill Yukhin <kirill.yukhin@intel.com>
> Date: Wed Mar 23 14:08:07 2016 +0300
>
> AVX2. Emit vpcmpeqd for const_m1 only if AVX2 is enabled.
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 1639704..963cc3d 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -10859,7 +10859,7 @@ standard_sse_constant_opcode (rtx_insn *insn, rtx x)
> || get_attr_mode (insn) == MODE_V8DF
> || get_attr_mode (insn) == MODE_V16SF)
> return "vpternlogd\t{$0xFF, %g0, %g0, %g0|%g0, %g0, %g0, 0xFF}";
> - if (TARGET_AVX)
> + if (TARGET_AVX2 || get_attr_mode (insn) == 16)
> return "vpcmpeqd\t%0, %0, %0";
> else
> return "pcmpeqd\t%0, %0";
Jakub