Date: Sun, 30 Mar 2008 18:07:12 +0000 (UTC) From: Bruce Evans <bde@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/lib/msun/src e_hypot.c e_hypotf.c Message-ID: <200803301807.m2UI7CNR007979@repoman.freebsd.org>
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bde 2008-03-30 18:07:12 UTC
FreeBSD src repository
Modified files:
lib/msun/src e_hypot.c e_hypotf.c
Log:
Use fabs[f]() instead of bit fiddling for setting absolute values.
This makes little difference in float precision, but in double
precision gives a speedup of about 30% on amd64 (A64 CPU) and i386
(A64). This depends on fabs[f]() being inline and efficient. The
bit fiddling (or any use of SET_HIGH_WORD(), which libm does too
much because it was best on old 32-bit machines) always causes
packing overheads and sometimes causes stalls in the packing, since
it operates on only part of a variable in the double precision case.
It apparently did cause stalls in a critical path here.
Revision Changes Path
1.12 +2 -2 src/lib/msun/src/e_hypot.c
1.13 +2 -2 src/lib/msun/src/e_hypotf.c
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