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From: "dcb314 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/112550] New: Difference in output from -O0 to -01 ?
Date: Wed, 15 Nov 2023 16:48:10 +0000 [thread overview]
Message-ID: <bug-112550-4@http.gcc.gnu.org/bugzilla/> (raw)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112550
Bug ID: 112550
Summary: Difference in output from -O0 to -01 ?
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: dcb314 at hotmail dot com
Target Milestone: ---
Created attachment 56594
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56594&action=edit
C source code
For the attached C code, with this bash script:
$ cat qwe.sh
CC="/home/dcb38/gcc/results/bin/gcc"
FLAGS="-w -ftrivial-auto-var-init=zero -fno-strict-aliasing"
echo bug 981
$CC -O0 $FLAGS bug981.c -o 1.exe
$CC -O1 $FLAGS bug981.c -o 2.exe
./1.exe 1 > 1.out
./2.exe 1 > 2.out
diff 1.out 2.out | head -5
$ source ./qwe.sh
bug 981
38c38
< ...checksum after hashing g_130[i][j] : 19463610
---
> ...checksum after hashing g_130[i][j] : 65FD073B
40c40
$ /home/dcb38/gcc/results/bin/gcc -v 2>&1 | grep exp
gcc version 14.0.0 20231115 (experimental) (081fddbbcf979022)
$
I don't understand why such a trivial change from -O0 to -O1 would cause
such a difference.
Is there perhaps another -f flag I should use to get no difference ?
next reply other threads:[~2023-11-15 16:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-15 16:48 dcb314 at hotmail dot com [this message]
2023-11-15 16:49 ` [Bug c/112550] " sjames at gcc dot gnu.org
2023-11-15 16:59 ` dcb314 at hotmail dot com
2023-11-15 17:10 ` dcb314 at hotmail dot com
2023-11-15 22:42 ` xry111 at gcc dot gnu.org
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