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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/107608] [13 Regression] Failure on fold-overflow-1.c and pr95115.c Date: Fri, 16 Dec 2022 13:20:25 +0000 [thread overview] Message-ID: <bug-107608-4-opawSz5fWB@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-107608-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107608 --- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Some extra food for thought: void bar (void); void foo (double x) { if (x >= -16.0 && x <= 16.0) { double y = x + 32.0; double z = y * 42.5; if (z < 600.0 || z > 3000.0) bar (); } } with the usual default -O2 aka -O2 -ftrapping-math. frange can correctly prove that bar () will be never called and with -O2 -fno-trapping-math it is perfectly fine to optimize the whole function out, z is known to be [680., 2040.] and not NaN. Now, even the comparisons aren't strictly needed, comparisons trap only on NaNs (< and > are not quiet, so any kind of them, but after all, frange doesn't track sNaNs vs. qNaNs) and we know z is not NaN. But x comparisons can raise invalid on NaNs (both qNaN and sNaN), the addition is known not to raise invalid (x is not NaN), nor overflow (limited range), not sure right now if it can raise underflow or inexact, but at least the latter quite possibly. The multiplication I'm quite sure can raise inexact though, so I think we need to keep everything until the z = computation, and either replace the comparison(s) of z with some dummy (asm?) use of z, or keep the comparisons but say turn the bar () call into __builtin_unreachable () or __builtin_trap () and make sure we don't optimize away the former later? The reason I want to show this is mainly that even when the actual operation (comparisons here) we'd like to fold into constant are known not to raise any exceptions (and we should use frange info to find that out), it might be some intermediate calculation that might still raise exceptions. I was considering to do some hack at least in my Fedora test mass rebuilds this month like for flag_trapping_math pretend no floating point range is singleton, but that still wouldn't cover comparisons.
next prev parent reply other threads:[~2022-12-16 13:20 UTC|newest] Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-11-10 9:47 [Bug tree-optimization/107608] New: [13 Regression] Failure on fold-overflow-1.c jakub at gcc dot gnu.org 2022-11-10 9:49 ` [Bug tree-optimization/107608] " jakub at gcc dot gnu.org 2022-11-10 13:47 ` rguenth at gcc dot gnu.org 2022-11-10 18:13 ` pinskia at gcc dot gnu.org 2022-11-11 7:18 ` pinskia at gcc dot gnu.org 2022-11-13 6:30 ` [Bug tree-optimization/107608] [13 Regression] Failure on fold-overflow-1.c and pr95115.c xry111 at gcc dot gnu.org 2022-11-28 10:06 ` rguenth at gcc dot gnu.org 2022-12-05 13:22 ` aldyh at gcc dot gnu.org 2022-12-05 15:14 ` rguenth at gcc dot gnu.org 2022-12-05 16:30 ` aldyh at gcc dot gnu.org 2022-12-16 13:20 ` jakub at gcc dot gnu.org [this message] 2022-12-16 13:32 ` rguenth at gcc dot gnu.org 2023-01-09 15:18 ` aldyh at gcc dot gnu.org 2023-01-10 8:56 ` rguenth at gcc dot gnu.org 2023-01-10 8:58 ` rguenth at gcc dot gnu.org 2023-01-10 10:20 ` aldyh at gcc dot gnu.org 2023-01-10 10:25 ` aldyh at gcc dot gnu.org 2023-01-10 11:00 ` rguenth at gcc dot gnu.org 2023-01-10 11:09 ` jakub at gcc dot gnu.org 2023-01-10 12:08 ` rguenther at suse dot de 2023-01-10 14:14 ` jakub at gcc dot gnu.org 2023-01-10 14:25 ` amacleod at redhat dot com 2023-01-10 14:33 ` aldyh at gcc dot gnu.org 2023-01-10 14:39 ` jakub at gcc dot gnu.org 2023-01-10 14:40 ` aldyh at gcc dot gnu.org 2023-01-10 14:42 ` jakub at gcc dot gnu.org 2023-01-12 11:42 ` aldyh at gcc dot gnu.org 2023-01-12 12:03 ` jakub at gcc dot gnu.org 2023-01-12 12:26 ` xry111 at gcc dot gnu.org 2023-01-13 13:19 ` aldyh at gcc dot gnu.org 2023-01-13 13:25 ` aldyh at gcc dot gnu.org 2023-01-15 15:43 ` cvs-commit at gcc dot gnu.org 2023-01-16 21:38 ` romain.geissler at amadeus dot com 2023-01-16 21:46 ` jakub at gcc dot gnu.org 2023-01-16 21:55 ` romain.geissler at amadeus dot com 2023-01-16 21:58 ` fw at gcc dot gnu.org 2023-01-18 12:26 ` aldyh at gcc dot gnu.org 2023-01-18 12:54 ` jakub at gcc dot gnu.org 2023-01-18 12:56 ` aldyh at gcc dot gnu.org 2023-01-18 13:00 ` rguenth at gcc dot gnu.org 2023-01-18 13:03 ` rguenth at gcc dot gnu.org 2023-01-18 13:05 ` rguenth at gcc dot gnu.org 2023-01-19 1:15 ` xry111 at gcc dot gnu.org 2023-01-19 7:17 ` rguenther at suse dot de 2023-01-26 14:29 ` xry111 at gcc dot gnu.org 2023-01-27 7:35 ` rguenth at gcc dot gnu.org 2023-01-27 7:59 ` xry111 at gcc dot gnu.org 2023-01-27 9:53 ` rguenther at suse dot de 2023-01-27 10:02 ` xry111 at gcc dot gnu.org 2023-01-27 10:13 ` jakub at gcc dot gnu.org 2023-01-27 11:30 ` rguenther at suse dot de
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