http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55839
Bug #: 55839
Summary: Inefficiency with array constructor
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: fortran
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: tkoe...@gcc.gnu.org
This idiom
subroutine foo(a,b,c,n)
integer, intent(in) :: n
real, intent(in), dimension(n) :: a,b
real, intent(out), dimension(2*n) :: c
c(1:2*n) = [a(1:n), b(1:n)]
end subroutine foo
builds an array using malloc and copies the data two times.
It would be better to express this as
c(1:n) = a(1:n)
c(n+1:2*n) = b(1:n)
Looks like a job for front-end optimization; it would be a bit
hard to expect the middle-end to optimize away all the calls
to malloc etc.
