[flang] implement simple pointer assignments inside FORALL (#129522)

The semantic of pointer assignments inside FORALL requires evaluating
the targets (RHS) and pointer variables (LHS) of all iterations before
evaluating the assignments.

In practice, if the compiler can prove that the RHS and LHS evaluations
are not impacted by the assignments, the evaluation of the FORALL
assignment statement can be done in a single loop. However, if the
compiler cannot prove this, it needs to "save" the addresses of the
targets and/or the pointer descriptors of each iterations before doing
the assignments.

This patch implements the most common cases where there is no lower bound
spec, no bounds remapping, the LHS is not polymorphic, and the RHS is
not NULL.

The HLFIR operation used to represent assignments inside FORALL can be
used for pointer assignments to (the only difference being that the LHS
is a descriptor address).

The analysis for intrinsic assignment can be reused, with the
distinction that the RHS data is not read during the assignment.

The logic that is used to save LHS in intrinsic assignments inside
FORALL is extracted to be used for the RHS of pointer assignments when
needed (saving a descriptor value).
Pointer assignment LHS are just descriptor addresses and are saved as
int_ptr values.

0 files changed, 0 insertions, 0 deletions