Diego Novillo wrote:
We have been bouncing ideas for a new mechanism to describe the behavior
of function calls so that optimizers can be more aggressive at call
sites. Currently, GCC supports the notion of pure/impure,
const/non-const, but that is not enough for various cases.
Fortran supports to mark function arguments as INTENT(IN), i.e. they are
not modified by the function, or INTENT(OUT), i.e. the variable is set
in the function - thus an assignment of a variable just before the
function call can be optimized away. (Especially, supporting INTENT(IN)
would be useful as by default all variables get passed by reference in
Fortran. See PR 23169.
Tobias
PS: Fortran has also the notion of PURE functions. And all objects which
are passed by reference or are ALLOCATABLE match C's restricted pointer,
unless they have the (pointer) TARGET or the POINTER attribute - only
then the same memory can be reached via more than one variable name.
