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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/99407] s243 benchmark of TSVC is vectorized by clang and not by gcc, missed DSE
Date: Mon, 08 Mar 2021 08:11:50 +0000	[thread overview]
Message-ID: <bug-99407-4-cr9IGDJ7ci@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-99407-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99407

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-03-08
     Ever confirmed|0                           |1
           Keywords|                            |missed-optimization
             Blocks|                            |53947
            Summary|s243 benchmark of TSVC is   |s243 benchmark of TSVC is
                   |vectorized by clang and not |vectorized by clang and not
                   |by gcc                      |by gcc, missed DSE
          Component|middle-end                  |tree-optimization
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, wonder why DSE didn't remove the first a[i] store.  Ah, because DSE
doesn't use data-ref analysis and thus cannot disambiguate the variable offset.

Manually applying DSE produces

.L4:
        vmovaps c(%rax), %ymm1
        vaddps  e(%rax), %ymm1, %ymm0
        addq    $32, %rax
        vmovups a-28(%rax), %ymm1
        vmulps  d-32(%rax), %ymm1, %ymm1
        vmulps  d-32(%rax), %ymm0, %ymm0
        vaddps  b-32(%rax), %ymm0, %ymm0
        vmovaps %ymm0, b-32(%rax)
        vaddps  %ymm0, %ymm1, %ymm0
        vmovaps %ymm0, a-32(%rax)
        cmpq    $127968, %rax
        jne     .L4


manually DSEd loop:

    for (int nl = 0; nl < iterations; nl++) {
        for (int i = 0; i < LEN_1D-1; i++) {
            real_t tem = b[i] + c[i  ] * d[i];
            b[i] = tem + d[i  ] * e[i];
            a[i] = b[i] + a[i+1] * d[i];
        }
    }


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations

  parent reply	other threads:[~2021-03-08  8:11 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-05 14:01 [Bug middle-end/99407] New: s243 benchmark of TSVC is vectorized by clang and not by gcc hubicka at gcc dot gnu.org
2021-03-05 14:04 ` [Bug middle-end/99407] " hubicka at gcc dot gnu.org
2021-03-08  8:11 ` rguenth at gcc dot gnu.org [this message]
2022-09-22 10:52 ` [Bug tree-optimization/99407] s243 benchmark of TSVC is vectorized by clang and not by gcc, missed DSE cvs-commit at gcc dot gnu.org
2022-09-22 10:53 ` rguenth at gcc dot gnu.org
2022-09-22 15:56 ` pinskia at gcc dot gnu.org
2023-12-12  3:18 ` pinskia at gcc dot gnu.org

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