This is a further improved patch series to that posted at: https://gcc.gnu.org/pipermail/gcc-patches/2024-September/662138.html
The main change is that the expansion of the iterators is pushed back further to the omp-lowering stage. This is because the recently committed deep-mapping support (and features such as strided array updates in the OpenMP development branch) do their work in the omplower stage, but the iterators need to be expanded after any changes to the clauses and their decls/sizes have occurred. This patch set does not support deep-mapping yet - it just emits a sorry when this happens.
The iterator expansion now does not happen all at once. A new loop is generated the first time a clause with a new iterator is found, and is reused if the same iterator is used in another clause. Assigning the clause decl and size in the iterator loop are now done by calling separate functions from lower_target, which also return the new hostaddr/size expression from the iterator loop that should be passed to libgomp. This fits in better with the existing code structure. A final function is called to finalise all the loops. As multiple sets of loops can be 'in-flight' at once, a new structure and a hash map are used to keep track of their states.
Instead of making the OMP_CLAUSE_DECL into a tree list with the iterator in TREE_PURPOSE and original decl in TREE_VALUE, I have stored the iterator in a third argument in the clause tree node addressed by OMP_CLAUSE_ITERATOR instead. In this way, changes do not have to be made in the intervening code-path to extract the original OMP_CLAUSE_DECL (which is messy and error-prone), allowing code unrelated to iterators to go unmodified. Nearly all special-cases for iterators have now been removed.
I have also fixed some issues detected by Linaro CI - some format specifier issues, and some tests that expect a non-unified target address space failing.
Gomp GCC tests and libgomp tests run on x86_64 host with Nvidia offloading. Okay for trunk?
Kwok
