http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48997
Summary: Don't use allocatable arrays for function elimination
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: fortran
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: tkoe...@gcc.gnu.org
Blocks: 36854
After revision 173752, double occurrence of functions returning arrays
within an expression are removed using an allocatable array as temporary.
It would be better to use BLOCK variables.
Example:
Transform
function optmatmul (a, b, ni, nj)
implicit none
integer, intent(in) :: ni, nj
double precision :: optmatmul(ni, nj)
double precision, intent(in) :: a(ni, nj), b(ni, nj)
optmatmul = matmul(a, b) / (1 + matmul(a, b))
end function optmatmul
(the test case from PR 22572) to
function optmatmul (a, b, c, m, n, count)
implicit none
integer, intent(in) :: m, n, count
double precision :: optmatmul(m, n)
double precision, intent(in) :: a(m, count), b(count, n), c(m, n)
block
double precision, dimension(size(a,1), size(b,2)) :: tmp
tmp = matmul(a,b)
optmatmul = tmp / (1 + tmp)
end block
end function optmatmul
We would probably need argument mapping for this.
Issues to be resolved:
- This is complicated, especially for intrinsics which take their
return size from their arguments
- Especially ugly: pack
- Also not nice: dim=n arguments where n is a variable
- We would need a way to handle functions in argument lists specifying
return dimensions, which we have to keep from being evaluated twice
(not a likely corner case, but we have to be correct...)
