public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c/99494] New: isfinite gets optimized away with -Ofast
@ 2021-03-09 19:01 arek_koz at o2 dot pl
2021-03-09 19:11 ` [Bug c/99494] " schwab@linux-m68k.org
2021-03-09 19:14 ` arek_koz at o2 dot pl
0 siblings, 2 replies; 3+ messages in thread
From: arek_koz at o2 dot pl @ 2021-03-09 19:01 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99494
Bug ID: 99494
Summary: isfinite gets optimized away with -Ofast
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: arek_koz at o2 dot pl
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
Build: x86_64-pc-linux-gnu
Created attachment 50342
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50342&action=edit
stripped _Py_HashDouble
CPython compiled with -Ofast hangs forever on python -c 'hash(float("inf"))'.
Attached is a program based on stripped _Py_HashDouble from CPython sources.
It should print 314159 when it reads an infinite number from the input.
It always prints 1 instead (the function gets reduced to "return 1").
When replacing -Ofast with -O3, the problem is gone. Likely to appear on other
build/host/target configurations.
Version: gcc (Gentoo 10.2.0-r5 p6) 10.2.0
Target architecture: x86_64 (generic)
GCC is compiled to execute on: x86_64 (znver2)
Invoked command: x86_64-pc-linux-gnu-gcc -Ofast -o bug bug.c
My best guess:
GCC -Ofast assumes that isfinite(v) is always true for any double v.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/99494] isfinite gets optimized away with -Ofast
2021-03-09 19:01 [Bug c/99494] New: isfinite gets optimized away with -Ofast arek_koz at o2 dot pl
@ 2021-03-09 19:11 ` schwab@linux-m68k.org
2021-03-09 19:14 ` arek_koz at o2 dot pl
1 sibling, 0 replies; 3+ messages in thread
From: schwab@linux-m68k.org @ 2021-03-09 19:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99494
Andreas Schwab <schwab@linux-m68k.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #1 from Andreas Schwab <schwab@linux-m68k.org> ---
-Ofast implies -ffinite-math-only.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/99494] isfinite gets optimized away with -Ofast
2021-03-09 19:01 [Bug c/99494] New: isfinite gets optimized away with -Ofast arek_koz at o2 dot pl
2021-03-09 19:11 ` [Bug c/99494] " schwab@linux-m68k.org
@ 2021-03-09 19:14 ` arek_koz at o2 dot pl
1 sibling, 0 replies; 3+ messages in thread
From: arek_koz at o2 dot pl @ 2021-03-09 19:14 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99494
--- Comment #2 from arek_koz at o2 dot pl ---
Sorry for trouble, my bad.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-03-09 19:14 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-03-09 19:01 [Bug c/99494] New: isfinite gets optimized away with -Ofast arek_koz at o2 dot pl
2021-03-09 19:11 ` [Bug c/99494] " schwab@linux-m68k.org
2021-03-09 19:14 ` arek_koz at o2 dot pl
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).