This patch updates printing and parsing of operations including clauses
that define entry block arguments to the operation's region. This
impacts `in_reduction`, `map`, `private`, `reduction` and
`task_reduction`.
The proposed representation to be used by all such clauses is the
following:
```
<clause_name>([byref] [@<sym>] %value -> %block_arg [, ...] : <type>[, ...]) {
...
}
```
The `byref` tag is only allowed for reduction-like clauses and the
`@<sym>` is required and only allowed for the `private` and
reduction-like clauses. The `map` clause does not accept any of these
two.
This change fixes some currently broken op representations, like
`omp.teams` or `omp.sections` reduction:
```
omp.teams reduction([byref] @<sym> -> %value : <type>) {
^bb0(%block_arg : <type>):
...
}
```
Additionally, it addresses some redundancy in the representation of the
previously mentioned cases, as well as e.g. `map` in `omp.target`. The
problem is that the block argument name after the arrow is not checked
in any way, which makes some misleading representations legal:
```mlir
omp.target map_entries(%x -> %arg1, %y -> %arg0, %z -> %doesnt_exist : !llvm.ptr, !llvm.ptr, !llvm.ptr) {
^bb0(%arg0 : !llvm.ptr, %arg1 : !llvm.ptr, %arg2 : !llvm.ptr):
...
}
```
In that case, `%x` maps to `%arg0`, contrary to what the representation
states, and `%z` maps to `%arg2`. `%doesnt_exist` is not resolved, so it
would likely cause issues if used anywhere inside of the operation's
region.
The solution implemented in this patch makes it so that values
introduced after the arrow on the representation of these clauses
implicitly define the corresponding entry block arguments, removing the
potential for these problematic representations. This is what is already
implemented for the `private` and `reduction` clauses of `omp.parallel`.
There are a couple of consequences of this change:
- Entry block argument-defining clauses must come at the end of the
operation's representation and in alphabetical order. This is because
they are printed/parsed as part of the region and a standardized
ordering is needed to reliably match op arguments with their
corresponding entry block arguments via the `BlockArgOpenMPOpInterface`.
- We can no longer define per-clause assembly formats to be reused by
all operations that take these clauses, since they must be passed to a
custom printer including the region and arguments of all other entry
block argument-defining clauses. Code duplication and potential for
introducing issues is minimized by providing the generic
`{print,parse}BlockArgRegion` helpers and associated structures.
MLIR and Flang lowering unit tests are updated due to changes in the
order and formatting of impacted operations.
Flips the delayed privatization switch to be on by default. After the
recent fixes related to delayed privatization, the gfortran test suite
runs successfully with delayed privatization turned on by defuault for
`omp parallel`.
This PR contains 2 commits:
1. A commit to reapply changes introduced #91116 (was reverted earlier
due to test suite failures)
2. A commit containing a possible solution for the issue causing the
test suite failures. In particular, it introduces a simple symbol
visitor class to keep track of the current active OMP construct and
marking this active construct as the scope defining the symbol being
visisted.
HLFIR lowering always adds hlfir.declare when symbols are bound to their
address allocated on the stack. Ensure that the declare is placed along
with the alloca if it is hoisted. And always return the mlir value that
is bound to the symbol (i.e the alloca in FIR lowering and the declare
in HLFIR lowering).
Context: Loop index variables in OpenMP parallel regions should be
privatised to work correctly.
Reviewed By: tblah
Differential Revision: https://reviews.llvm.org/D158594
