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[Bug rtl-optimization/19210] [4.0 Regression] not using do-loop for some loops
- From: "dje at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 31 Dec 2004 23:55:38 -0000
- Subject: [Bug rtl-optimization/19210] [4.0 Regression] not using do-loop for some loops
- References: <20041230204442.19210.pinskia@gcc.gnu.org>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From dje at gcc dot gnu dot org 2004-12-31 23:55 -------
XLC includes the option
strict_induction
Turns off induction variable optimizations
that have the potential to alter the semantics of a
user's program. The default is "nostrict_induction" at
-O2 or higher and "strict_induction" otherwise.
"nostrict_induction" is recomended if your program does
not have overflows or wrap arounds of loop induction
variables.
We probably need something similar in GCC. Note that XLC enables it when
optimizing.
Most programmers do not expect to be limited by the undefined wrapping behavior.
They are not using the extremes.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19210