[PATCH][PR target/97642] Fix incorrect replacement of vmovdqu32 with vpblendd.

[Jeff Law]

On 11/4/20 2:19 AM, Hongtao Liu via Gcc-patches wrote:
> Hi:
>   When programmers explicitly use mask loaded intrinsics, don't
> transform the instruction to vpblend{b,w,d,q} since If mem_addr points
> to a memory region with less than whole vector size of accessible
> memory,  the mask would prevent reading the inaccessible bytes which
> could avoid fault.
>
>   Bootstrap is ok, gcc regress test for i386/x86_64 backend is ok.
>   Ok for trunk?
>
> gcc/ChangeLog:
>
>         PR target/97642
>         * config/i386/sse.md (UNSPEC_MASKLOAD): New unspec.
>         (*<avx512>_load<mode>_mask): New define_insns for masked load
>         instructions.
>         (<avx512>_load<mode>_mask): Changed to define_expands which
>         specifically handle memory operands.
>         (<avx512>_blendm<mode>): Changed to define_insns which are same
>         as original <avx512>_load<mode>_mask with adjustment of
>         operands order.
>         (*<avx512>_load<mode>): New define_insn_and_split which is
>         used to optimize for masked load with all one mask.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/i386/avx512bw-vmovdqu16-1.c: Adjust testcase to
>         make sure only masked load instruction is generated.
>         * gcc.target/i386/avx512bw-vmovdqu8-1.c: Ditto.
>         * gcc.target/i386/avx512f-vmovapd-1.c: Ditto.
>         * gcc.target/i386/avx512f-vmovaps-1.c: Ditto.
>         * gcc.target/i386/avx512f-vmovdqa32-1.c: Ditto.
>         * gcc.target/i386/avx512f-vmovdqa64-1.c: Ditto.
>         * gcc.target/i386/avx512vl-vmovapd-1.c: Ditto.
>         * gcc.target/i386/avx512vl-vmovaps-1.c: Ditto.
>         * gcc.target/i386/avx512vl-vmovdqa32-1.c: Ditto.
>         * gcc.target/i386/avx512vl-vmovdqa64-1.c: Ditto.
>         * gcc.target/i386/pr97642-1.c: New test.
>         * gcc.target/i386/pr97642-2.c: New test.
>
>
> 0001-Fix-incorrect-replacement-of-vmovdqu32-with-vpblendd.patch
>
> From 48cf0adcd55395653891888f4768b8bdc19786f2 Mon Sep 17 00:00:00 2001
> From: liuhongt <hongtao.liu@intel.com>
> Date: Tue, 3 Nov 2020 17:26:43 +0800
> Subject: [PATCH] Fix incorrect replacement of vmovdqu32 with vpblendd which
>  can cause fault.
>
> gcc/ChangeLog:
>
> 	PR target/97642
> 	* config/i386/sse.md (UNSPEC_MASKLOAD): New unspec.
> 	(*<avx512>_load<mode>_mask): New define_insns for masked load
> 	instructions.
> 	(<avx512>_load<mode>_mask): Changed to define_expands which
> 	specifically handle memory operands.
> 	(<avx512>_blendm<mode>): Changed to define_insns which are same
> 	as original <avx512>_load<mode>_mask with adjustment of
> 	operands order.
> 	(*<avx512>_load<mode>): New define_insn_and_split which is
> 	used to optimize for masked load with all one mask.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.target/i386/avx512bw-vmovdqu16-1.c: Adjust testcase to
> 	make sure only masked load instruction is generated.
> 	* gcc.target/i386/avx512bw-vmovdqu8-1.c: Ditto.
> 	* gcc.target/i386/avx512f-vmovapd-1.c: Ditto.
> 	* gcc.target/i386/avx512f-vmovaps-1.c: Ditto.
> 	* gcc.target/i386/avx512f-vmovdqa32-1.c: Ditto.
> 	* gcc.target/i386/avx512f-vmovdqa64-1.c: Ditto.
> 	* gcc.target/i386/avx512vl-vmovapd-1.c: Ditto.
> 	* gcc.target/i386/avx512vl-vmovaps-1.c: Ditto.
> 	* gcc.target/i386/avx512vl-vmovdqa32-1.c: Ditto.
> 	* gcc.target/i386/avx512vl-vmovdqa64-1.c: Ditto.
> 	* gcc.target/i386/pr97642-1.c: New test.
> 	* gcc.target/i386/pr97642-2.c: New test.
So in the BZ Jakub asked for the all-ones mask case to be specially
handled to emit a normal load.  I don't see where we're handling that. 
ISTM that we'd want a test for that too.  Right?

WIth that in place and tested, this is probably ready for the trunk.

jeff