Date: Tue, 20 Dec 2005 01:21:30 +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 s_cbrt.c Message-ID: <200512200121.jBK1LUTd050099@repoman.freebsd.org>
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bde 2005-12-20 01:21:30 UTC
FreeBSD src repository
Modified files:
lib/msun/src s_cbrt.c
Log:
Extract the high and low words together. With gcc-3.4 on uniformly
distributed non-large args, this saves about 14 of 134 cycles for
Athlon64s and about 5 of 199 cycles for AthlonXPs.
Moved the check for x == 0 inside the check for subnormals. With
gcc-3.4 on uniformly distributed non-large args, this saves another
5 cycles on Athlon64s and loses 1 cycle on AthlonXPs.
Use INSERT_WORDS() and not SET_HIGH_WORD() when converting the first
approximation from bits to double. With gcc-3.4 on uniformly distributed
non-large args, this saves another 4 cycles on both Athlon64s and and
AthlonXPs.
Accessing doubles as 2 words may be an optimization on old CPUs, but on
current CPUs it tends to cause extra operations and pipeline stalls,
especially for writes, even when only 1 of the words needs to be accessed.
Removed an unused variable.
Revision Changes Path
1.14 +6 -8 src/lib/msun/src/s_cbrt.c
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