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[Bug tree-optimization/40087] [4.3/4.4/4.5 Regression] Number of iterations analysis wrong
- From: "rakdver at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 15 May 2009 00:34:19 -0000
- Subject: [Bug tree-optimization/40087] [4.3/4.4/4.5 Regression] Number of iterations analysis wrong
- References: <bug-40087-17694@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #6 from rakdver at gcc dot gnu dot org 2009-05-15 00:34 -------
(In reply to comment #5)
> It is number of iteration analysis that gets it wrong (I suppose it might get
> confused by the two exits of the loop?).
Sort of; # of iterations analysis assumes that pointers never wrap, and uses
this assumption to derive a wrong number of iterations for the first exit
(which is not taken). We had a similar problem before (PR 25985), but I
somehow persuaded myself that this cannot happen with pointers.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40087