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From: "steinar+gcc at gunderson dot no" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/94956] Unable to remove impossible ffs() test for zero
Date: Sun, 20 Jun 2021 09:50:06 +0000	[thread overview]
Message-ID: <bug-94956-4-lZENdVttlm@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-94956-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94956

--- Comment #7 from Steinar H. Gunderson <steinar+gcc at gunderson dot no> ---
To wrap this up, confirming that GCC 11 does well on my benchmark:

BM_Chain20            54529 iterations      18781 ns/iter   GCC 10, asm bsfq
BM_Chain20            44584 iterations      22509 ns/iter   GCC 10, ffsll()
BM_Chain20            49753 iterations      20216 ns/iter   GCC 11, asm bsfq
BM_Chain20            53346 iterations      18816 ns/iter   GCC 11, ffsll()
BM_Chain20            64926 iterations      15747 ns/iter   Clang 12, asm bsfq
BM_Chain20            71208 iterations      14374 ns/iter   Clang 12, ffsll()

So basically for 11+, the ffsll() statement does better than the bsfq
statement, whereas it used to do markedly worse.

Clang does even better, but I can live with that. :-)

  parent reply	other threads:[~2021-06-20  9:50 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-05 15:38 [Bug tree-optimization/94956] New: " steinar+gcc at gunderson dot no
2020-05-05 15:39 ` [Bug tree-optimization/94956] " steinar+gcc at gunderson dot no
2020-05-05 17:21 ` jakub at gcc dot gnu.org
2020-05-05 18:21 ` jakub at gcc dot gnu.org
2020-05-06  6:58 ` rguenth at gcc dot gnu.org
2020-05-08  7:34 ` cvs-commit at gcc dot gnu.org
2020-05-08  7:51 ` jakub at gcc dot gnu.org
2020-05-08  7:53 ` steinar+gcc at gunderson dot no
2021-06-20  9:50 ` steinar+gcc at gunderson dot no [this message]
2021-08-03  2:09 ` pinskia at gcc dot gnu.org

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