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[Bug regression/71231] [7 Regression]: 300% runtime increase for rnflow
- From: "glisse at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Tue, 24 May 2016 06:48:54 +0000
- Subject: [Bug regression/71231] [7 Regression]: 300% runtime increase for rnflow
- Auto-submitted: auto-generated
- References: <bug-71231-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71231
--- Comment #12 from Marc Glisse <glisse at gcc dot gnu.org> ---
-fwrapv seems to fix it. As far as I can tell, the multiplication is done in 32
bits, VRP detects that the numbers are nonnegative, so zeroing the sign bit of
the result of the mult+add can be assumed to be a NOP.