The following test case does not vectorize:
integer, parameter :: n = 1000000
integer :: i, j, k
real(8) :: pi, sum1, sum2, theta, phi, sini, cosi, dotp
real(8) :: a(3), b(9,3), c(3)
pi = acos(-1.0d0)
theta = pi/9.0d0
phi = pi/4.5d0
do k = 1, 9
b(k,1) = 0.5d0*cos(k*phi)*sin(k*theta)
b(k,2) = 0.5d0*sin(k*phi)*sin(k*theta)
b(k,3) = 0.5d0*cos(k*theta)
end do
theta = pi/real(n,kind=8)
sum2 = 0.0
do i = 1, n
sini = sin(i*theta)
cosi = cos(i*theta)
phi = pi/4.5d0
sum1 = 0.0d0
do j = 1, 9
c(1) = 0.5d0*cos(j*phi)*sini
c(2) = 0.5d0*sin(j*phi)*sini
c(3) = 0.5d0*cosi
do k =1, 9
a(1) = b(k,1) - c(1)
a(2) = b(k,2) - c(2)
a(3) = b(k,3) - c(3)
! a = b(k,:) - c
dotp = a(1)*a(1) + a(2)*a(2) + a(3)*a(3)
! dotp = dot_product(a,a)
sum1 = sum1 +dotp
end do
end do
sum2 = sum2 + sum1/81.0d0
end do
print *, 3.0d0*sum2/(4.0d0*pi*real(n,kind=8))
end
[ibook-dhum] bug/timing% gfc -O3 -ffast-math -funroll-loops -ftree-loop-linear
-ftree-vectorizer-verbose=2 test_vect.f90
test_vect.f90:20: note: not vectorized: unsupported data-type complex(kind=8)
test_vect.f90:8: note: not vectorized: unsupported data-type complex(kind=8)
test_vect.f90:1: note: vectorized 0 loops in function.
while it vectorize for
do k =1, 9
! a(1) = b(k,1) - c(1)
! a(2) = b(k,2) - c(2)
! a(3) = b(k,3) - c(3)
a = b(k,:) - c
dotp = a(1)*a(1) + a(2)*a(2) + a(3)*a(3)
! dotp = dot_product(a,a)
sum1 = sum1 +dotp
end do
[ibook-dhum] bug/timing% gfc -O3 -ffast-math -funroll-loops -ftree-loop-linear
-ftree-vectorizer-verbose=2 test_vect.f90
test_vect.f90:24: note: LOOP VECTORIZED.
test_vect.f90:8: note: not vectorized: unsupported data-type complex(kind=8)
test_vect.f90:1: note: vectorized 1 loops in function.
(see http://gcc.gnu.org/ml/gcc-patches/2008-05/msg00033.html and pr34265).
Note that both variants do not vectorize on powerpc-apple-darwin9.
--
Summary: [4.4 Regression] early loop unrolling pass prevents
vectorization
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: dominiq at lps dot ens dot fr
GCC build triplet: i686-apple-darwin9
GCC host triplet: i686-apple-darwin9
GCC target triplet: i686-apple-darwin9
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36099
