See also: http://gcc.gnu.org/ml/fortran/2006-12/msg00000.html
Tim Prince's analysis why ifort needs 8.77s and gfortran 12.16s for one
program:
"My copy of gfortran makes separate scalar calls to sin and cos, where ifort
makes a vector sincos call. 2 seconds to be gained there"
In the Fortran program below, a there is a call to the same argument with sin
and with cos. The resulting
gfortran -msse3 -march=opteron -ffast-math -O3 -c -fdump-tree-optimized
shows
pretmp.56 = __builtin_sinf (pretmp.80);
pretmp.86 = __builtin_cosf (pretmp.80);
Using sincos should be faster.
Fortran program:
subroutine
test(number_of_sample_points,radius,coefficient,radius_of_curvature,spin_frequency,time,tmp)
implicit none
integer :: number_of_sample_points
real, parameter :: twopi = 6.28319
integer :: n
real :: radius(number_of_sample_points), coefficient, radius_of_curvature, &
spin_frequency,time,tmp(2,number_of_sample_points)
do n = 1, number_of_sample_points
coefficient = (radius(n) / radius_of_curvature) * sin(twopi * &
spin_frequency * time)
tmp(1,n) = coefficient
coefficient = twopi * spin_frequency * (radius(n) / &
radius_of_curvature) * cos(twopi * &
spin_frequency * time)
tmp(2,n) = coefficient
end do
end subroutine
--
Summary: Call to sin(x), cos(x) should be transformed to
sincos(x)
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: burnus at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30038
