On 11/16/20 8:10 PM, Hongtao Liu wrote:
> On Tue, Nov 17, 2020 at 8:05 AM Jeff Law <l...@redhat.com> wrote:
>>
>> On 9/2/20 3:34 AM, Hongtao Liu via Gcc-patches wrote:
>>> Hi:
>>> Add define_peephole2 to eliminate potential redundant conversion
>>> from mask to vector.
>>> Bootstrap is ok, regression test is ok for i386/x86-64 backend.
>>> Ok for trunk?
>>>
>>> gcc/ChangeLog:
>>> PR target/96891
>>> * config/i386/sse.md (VI_128_256): New mode iterator.
>>> (define_peephole2): Lower avx512 vector compare to avx version
>>> when dest is vector.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> * gcc.target/i386/avx512bw-pr96891-1.c: New test.
>>> * gcc.target/i386/avx512f-pr96891-1.c: New test.
>>> * gcc.target/i386/avx512f-pr96891-2.c: New test.
>> Aren't these the two insns in question:
>>
>>
>> (insn 7 4 8 2 (set (reg:QI 86)
>> (unspec:QI [
>> (reg:V8SF 90)
>> (reg:V8SF 89)
>> (const_int 2 [0x2])
>> ] UNSPEC_PCMP)) "j.c":4:14 1911 {avx512vl_cmpv8sf3}
>> (expr_list:REG_DEAD (reg:V8SF 90)
>> (expr_list:REG_DEAD (reg:V8SF 89)
>> (nil))))
>> (note 8 7 9 2 NOTE_INSN_DELETED)
>> (insn 9 8 14 2 (set (reg:V8SI 82 [ _2 ])
>> (vec_merge:V8SI (const_vector:V8SI [
>> (const_int -1 [0xffffffffffffffff]) repeated x8
>> ])
>> (const_vector:V8SI [
>> (const_int 0 [0]) repeated x8
>> ])
>> (reg:QI 86))) "j.c":4:14 2705 {*avx512vl_cvtmask2dv8si}
>> (expr_list:REG_DEAD (reg:QI 86)
>> (nil)))
>>
>>
>> Note there's a data dependency between them. insn 7 feeds insn 9. When
>> there's a data dependency, combiner patterns are usually the better
>> choice than peepholes. I think you'd be looking to match something
>> likethis (from the . combine dump):
>>
>> (set (reg:V8SI 82 [ _2 ])
>> (vec_merge:V8SI (const_vector:V8SI [
>> (const_int -1 [0xffffffffffffffff]) repeated x8
>> ])
>> (const_vector:V8SI [
>> (const_int 0 [0]) repeated x8
>> ])
>> (unspec:QI [
>> (reg:V8SF 90)
>> (reg:V8SF 89)
>> (const_int 2 [0x2])
>> ] UNSPEC_PCMP)))
>>
>>
>> Jeff
>>
> Yes, as discussed in [1], maybe it's better to refactor avx512 integer
> mask with VnBImode. Then unspec_pcmp could be dropped and simplify_rtx
> could handle vector comparison more effectively.
>
> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97521#c4
Thanks for the pointer. I didn't realize this patch was essentially
abandoned.
Jeff
