public inbox for gcc-prs@sourceware.org help / color / mirror / Atom feed
From: mia@de.uu.net To: gcc-gnats@gcc.gnu.org Subject: optimization/9041: gcc 3.2.1: inconsistent behaviour with/without -O2 Date: Mon, 23 Dec 2002 04:16:00 -0000 [thread overview] Message-ID: <20021223121253.10345.qmail@sources.redhat.com> (raw) >Number: 9041 >Category: optimization >Synopsis: gcc 3.2.1: inconsistent behaviour with/without -O2 >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Mon Dec 23 04:16:01 PST 2002 >Closed-Date: >Last-Modified: >Originator: Michael van Acken >Release: gcc version 3.2.1 >Organization: >Environment: OS: Linux 2.4.19 CPU: Athlon-XP 1800+ >Description: Output of program should be 1065353216 but it is 134518336 not equal with -O2 (at least for me). #include <stdio.h> int main() { float y = 1.0f; int i = *(int*)&y; printf("%d\n", i); if (({int x = i; *(float*)&x;}) != 1.0f) { printf("not equal\n"); }; return 0; } >How-To-Repeat: ~/local/bin/gcc -Wall -O2 Val5.c && ./a.out >Fix: Remove -O2. Add -march=athlonxp. Run gcc-2.95 with -O2. And, most interestingly: Remove the "if" statement before the return. All these variants give the expected result. >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2002-12-23 12:16 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-12-23 4:16 mia [this message] 2002-12-23 5:14 ebotcazou
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20021223121253.10345.qmail@sources.redhat.com \ --to=mia@de.uu.net \ --cc=gcc-gnats@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
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).