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[Bug tree-optimization/59747] [4.9 Regression] wrong code at -Os and above on x86_64-linux-gnu in 64-bit mode
- From: "rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 10 Jan 2014 11:05:00 +0000
- Subject: [Bug tree-optimization/59747] [4.9 Regression] wrong code at -Os and above on x86_64-linux-gnu in 64-bit mode
- Auto-submitted: auto-generated
- References: <bug-59747-4 at http dot gcc dot gnu dot org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59747
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Marek Polacek from comment #2)
> I think the problem is in setting the value of e. With -O in .gimple we
> have:
> e.2 = e;
> e.3 = e.2;
> e.4 = e.3 + -1;
> e = e.4;
> while with -O2:
> e.2 = e;
> e.3 = e.2;
> e.4 = (unsigned short) e.3;
> D.1762 = e.4 + 65535;
> e.5 = (short int) D.1762;
> e = e.5;
That's -fstrict-overflows effect I think, but not the issue. "Fixed" by
-fno-ree.