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[Bug target/34702] 1.0 is not the inverse of 1.0 with -mrecip on x86
- From: "dominiq at lps dot ens dot fr" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 8 Jan 2008 14:20:23 -0000
- Subject: [Bug target/34702] 1.0 is not the inverse of 1.0 with -mrecip on x86
- References: <bug-34702-12313@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #7 from dominiq at lps dot ens dot fr 2008-01-08 14:20 -------
> the NR enhanced reciprocals provide adequate precision with great speedup
Two quick remarks along this line:
(1) On Core2Duo the speedup is not obvious for the polyhedron testsuite,
excepted for gas_dyn 7.7s vs. 8.5s (also capacita 59.6s vs. 57s).
(2) ifort seems to make an extensive use of this optimization (gas_dyn 4.1s),
in general with "packed" code, but seems to use 'div' also in other places.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34702