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[Bug tree-optimization/24123] [4.1 Regression] Massive performance regression for -ffast-math due to the recip tree pass
- From: "uros at kss-loka dot si" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 30 Sep 2005 13:58:54 -0000
- Subject: [Bug tree-optimization/24123] [4.1 Regression] Massive performance regression for -ffast-math due to the recip tree pass
- References: <20050929140549.24123.uros@kss-loka.si>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From uros at kss-loka dot si 2005-09-30 13:58 -------
Looking at the differences, the result of recip looks _really_ good!
Currently, there seems to be some problems, i.e.:
double pov::f_polytubes(double*, unsigned int) (ptr, D.22748)
- D.22787_46 = -6.28318530717958623199592693708837032318115234375e+0 / D.22783_80;
+ reciptmp.882_72 = 1.0e+0 / D.22783_80;
+ D.22787_46 = -6.28318530717958623199592693708837032318115234375e+0 *
reciptmp.882_72;
Not needed, only one user.
Function double pov::POVFPU_RunDefault(pov::FUNCTION)
<L193>:;
- r0_1660 = r0_89 / r0_89;
+ reciptmp.492_84 = 1.0e+0 / r0_89;
+ r0_1660 = r0_89 * reciptmp.492_84;
goto <bb 1062> (<L1339>);
The result of above confusion is (1.0)! We are in fast-math, so no NaNs, etc..
void pov::Simulate_Media(pov::IMEDIA**, pov::RAY*, pov::INTERSECTION*
- reciptmp.1152_907 = 1.0e+0 / prephitmp.1124_293;
- reciptmp.1153_1046 = 1.0e+0 / prephitmp.1124_293;
- reciptmp.1154_1041 = 1.0e+0 / prephitmp.1124_293;
+ reciptmp.1275_1270 = 1.0e+0 / prephitmp.1124_293;
+ reciptmp.1152_907 = 1.0e+0 * reciptmp.1275_1270;
+ reciptmp.1153_1046 = 1.0e+0 * reciptmp.1275_1270;
+ reciptmp.1154_1041 = 1.0e+0 * reciptmp.1275_1270;
These are all the same? There are already reciptmp variables in loopdone that
are all the same. And there are quite some places that have this problem.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24123