The Fortran front end presently linearizes accesses to
multi-dimensional arrays by combining the indices for the various
dimensions into a series of explicit multiplies and adds with
refactoring to allow CSE of invariant parts of the computation.
Unfortunately this representation interferes with Graphite-based loop
optimizations. It is difficult to recover the original
multi-dimensional form of the access by the time loop optimizations
run because parts of it have already been optimized away or into a
form that is not easily recognizable, so it seems better to have the
Fortran front end produce delinearized accesses to begin with, a set
of nested ARRAY_REFs similar to the existing behavior of the C and C++
front ends. This is a long-standing problem that has previously been
discussed e.g. in PR 14741 and PR61000.
This patch is an initial implementation for explicit array accesses
only; it doesn't handle the accesses generated during scalarization of
whole-array or array-section operations, which follow a different code
path.
gcc/
* expr.cc (get_inner_reference): Handle NOP_EXPR like
VIEW_CONVERT_EXPR.
gcc/fortran/
* lang.opt (-param=delinearize=): New.
* trans-array.cc (get_class_array_vptr): New, split from...
(build_array_ref): ...here.
(get_array_lbound, get_array_ubound): New, split from...
(gfc_conv_array_ref): ...here. Additional code refactoring
plus support for delinearization of the array access.
projects / thirdparty / gcc.git / commit
