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[Bug tree-optimization/24123] [4.1/4.2 Regression] Massive performance regression for -ffast-math due to the recip tree pass
- From: "dje at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 3 Jan 2006 15:22:50 -0000
- Subject: [Bug tree-optimization/24123] [4.1/4.2 Regression] Massive performance regression for -ffast-math due to the recip tree pass
- References: <bug-24123-1649@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #22 from dje at gcc dot gnu dot org 2006-01-03 15:22 -------
Is it possible for backends to inquire how many reciprocals were discovered?
PowerPC and IA-64 have reciprocal instructions and could benefit by choosing to
generate reciprocal earlier with additional information about the number of
divides calculated. For PowerPC, it is effective to use the instruction if
there are multiple divides, such as the three divisions mentioned above. The
IBM XLC compiler propagates the reciprocal and numerator pair through its
equivalent to RTL.
--
dje at gcc dot gnu dot org changed:
What |Removed |Added
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CC| |dje at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24123