https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92087
Bug ID: 92087
Summary: Do front-end optimization and warnings using basic
blocks and value or propagation
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: tkoenig at gcc dot gnu.org
Target Milestone: ---
Doing some optimization work in the front end using
value propagation could be a win.
For example, an error could be issued for
allocate (a(100))
do i=0,100
a(i) =...
or we could make sure never to warn for
real :: a(6)
do i=1,5
if (i < 6) a(i) = 42.
if we had range propagation.
This could also help with
subroutine foo (a,n)
real :: a(n)
...
do i=,n
a(n+1) = a(n) + 1.
end do
which we currently do not warn about because it would
be legal if the user changed n before reaching the DO
loop.
Regarding optimization, we should not try to do what the
middle-end already does, so the focus should be on
Fortran-specific constructs, especially array handling.
