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From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/106902] [11/12/13/14 Regression] Program compiled with -O3 -mfma produces different result
Date: Thu, 11 May 2023 17:32:51 +0000	[thread overview]
Message-ID: <bug-106902-4-sOPVGwJwN9@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-106902-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106902

--- Comment #20 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
I missed it the first time around, but placing PAREN_EXPR around the complete
expression won't work: nothing will prevent GCC from duplicating evaluations of
the sub-expressions, and then randomly forming FMAs like here. It would just
bury this class of bugs deeper.

Now that we are in stage1, can we make some kind of progress here? Is there any
buy-in for:

1. Implementing fp-contract=on via GENERIC folding?
2. Defaulting to fp-contract=on instead of fp-contract=fast under -std=gnu*?
3. Enabling fp-contract=fast under -ffast-math?

  parent reply	other threads:[~2023-05-11 17:32 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-10 18:58 [Bug tree-optimization/106902] New: Program compiled with -O3 -fmfa " jhllawrence963 at gmail dot com
2022-09-10 19:07 ` [Bug target/106902] Program compiled with -O3 -mfma " pinskia at gcc dot gnu.org
2022-09-12  8:01 ` [Bug target/106902] [11/12/13 Regression] " rguenth at gcc dot gnu.org
2022-09-12 14:08 ` marxin at gcc dot gnu.org
2022-09-12 14:10 ` [Bug target/106902] [11/12 " marxin at gcc dot gnu.org
2022-09-13  7:06 ` [Bug target/106902] [11/12/13 " rguenth at gcc dot gnu.org
2022-09-14 15:20 ` amonakov at gcc dot gnu.org
2022-09-15  9:33 ` amonakov at gcc dot gnu.org
2022-09-17 18:19 ` jhllawrence963 at gmail dot com
2022-09-17 18:23 ` jhllawrence963 at gmail dot com
2022-09-19  7:08 ` rguenth at gcc dot gnu.org
2022-09-19  7:14 ` amonakov at gcc dot gnu.org
2022-09-19  7:25 ` rguenth at gcc dot gnu.org
2022-09-19  8:14 ` amonakov at gcc dot gnu.org
2022-09-19  9:44 ` rguenth at gcc dot gnu.org
2022-09-27 18:31 ` amonakov at gcc dot gnu.org
2022-09-29  6:41 ` rguenth at gcc dot gnu.org
2022-09-29 11:28 ` amonakov at gcc dot gnu.org
2022-09-29 13:39 ` rguenther at suse dot de
2022-09-30  6:17 ` amonakov at gcc dot gnu.org
2023-05-11 17:32 ` amonakov at gcc dot gnu.org [this message]
2023-05-12  6:27 ` [Bug target/106902] [11/12/13/14 " rguenth at gcc dot gnu.org
2023-05-17 18:49 ` amonakov at gcc dot gnu.org
2023-05-17 18:54 ` pinskia at gcc dot gnu.org
2023-05-18  5:53 ` rguenth at gcc dot gnu.org
2023-05-18  8:31 ` amonakov at gcc dot gnu.org
2023-05-18 16:03 ` amonakov at gcc dot gnu.org
2023-05-18 16:52 ` rguenther at suse dot de
2023-05-29 10:07 ` jakub at gcc dot gnu.org

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