In the following testcase:
subroutine sub(aa,bb,n,m)
implicit none
integer, intent(in) :: n,m
real, intent(inout) :: aa(n,m)
real, intent(in) :: bb(n,m)
integer :: i,j
do i = 1,m
do j= 2,n
aa(i,j)= aa(i,j-1)+bb(i,j-1)
enddo
enddo
end subroutine
end
The stride of the accesses in the inner-loop is a parameter (m is not a
compile-time known constant). As a result the data dataref analyzer reports:
"
failed: evolution of offset is not affine
...
base_address:
offset from base address:
constant offset from base address:
step:
aligned to:
base_object: (*aa_54(D))[0]
symbol tag: SMT.25
"
Any chance that the dataref analysis can return an (invariant) expression in
"step", so that further analysis could continue? (for example, the access in
the outer-loop is consecutive, so if we had an expression to represent the
inner-loop stride, we could vectorize the outer-loop).
--
Summary: Failing to represent the stride of a dataref when it is
not a constant
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: dorit at gcc dot gnu dot org
GCC build triplet: powerpc64-linux
GCC host triplet: powerpc64-linux
GCC target triplet: powerpc64-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33113
