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[Bug tree-optimization/24123] [4.1 Regression] Massive performance regression for -ffast-math due to the recip tree pass
- From: "paolo dot bonzini at lu dot unisi dot ch" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 30 Sep 2005 14:40:23 -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 paolo dot bonzini at lu dot unisi dot ch 2005-09-30 14:40 -------
Subject: Re: [4.1 Regression] Massive performance
regression for -ffast-math due to the recip tree pass
>>>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..
>>>
>>>
Can you prepare a patch to fold, that fixes this beauty? :-)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24123