[Clang][OpenMP] Insert alloca for kernel args at function entry block instead of the launch point.

If an inlined kernel is called in a loop, the launch point alloca would
lead to increasing stack us

[Clang][OpenMP] Insert alloca for kernel args at function entry block instead of the launch point.

If an inlined kernel is called in a loop, the launch point alloca would
lead to increasing stack usage every time the kernel is invoked. This
could make the application run out of stack space and crash. This problem
is fixed by using the alloca insertion point while creating the alloca instruction.

Fixes https://github.com/llvm/llvm-project/issues/60602

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D145820

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[OpenMP] Convert tests to opaque pointers (NFC)

Conversion performed using the script at:
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34

These are only tests where no manual fixup w

[OpenMP] Convert tests to opaque pointers (NFC)

Conversion performed using the script at:
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34

These are only tests where no manual fixup was required.

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[OpaquePtrs][Clang] Add -no-opaque-pointers to tests (NFC)

This adds -no-opaque-pointers to clang tests whose output will
change when opaque pointers are enabled by default. This is
intended to be p

[OpaquePtrs][Clang] Add -no-opaque-pointers to tests (NFC)

This adds -no-opaque-pointers to clang tests whose output will
change when opaque pointers are enabled by default. This is
intended to be part of the migration approach described in
https://discourse.llvm.org/t/enabling-opaque-pointers-by-default/61322/9.

The patch has been produced by replacing %clang_cc1 with
%clang_cc1 -no-opaque-pointers for tests that fail with opaque
pointers enabled. Worth noting that this doesn't cover all tests,
there's a remaining ~40 tests not using %clang_cc1 that will need
a followup change.

Differential Revision: https://reviews.llvm.org/D123115

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[OpenMPIRBuilder] Allocate temporary at the correct block in a nested parallel

The OpenMPIRBuilder has a bug. Specifically, suppose you have two nested openmp parallel regions (writing with MLIR for

[OpenMPIRBuilder] Allocate temporary at the correct block in a nested parallel

The OpenMPIRBuilder has a bug. Specifically, suppose you have two nested openmp parallel regions (writing with MLIR for ease)

```
omp.parallel {
%a = ...
omp.parallel {
use(%a)
}
}
```

As OpenMP only permits pointer-like inputs, the builder will wrap all of the inputs into a stack allocation, and then pass this
allocation to the inner parallel. For example, we would want to get something like the following:

```
omp.parallel {
%a = ...
%tmp = alloc
store %tmp[] = %a
kmpc_fork(outlined, %tmp)
}
```

However, in practice, this is not what currently occurs in the context of nested parallel regions. Specifically to the OpenMPIRBuilder,
the entirety of the function (at the LLVM level) is currently inlined with blocks marking the corresponding start and end of each
region.

```
entry:
...

parallel1:
%a = ...
...

parallel2:
use(%a)
...

endparallel2:
...

endparallel1:
...
```

When the allocation is inserted, it presently inserted into the parent of the entire function (e.g. entry) rather than the parent
allocation scope to the function being outlined. If we were outlining parallel2, the corresponding alloca location would be parallel1.

This causes a variety of bugs, including https://github.com/llvm/llvm-project/issues/54165 as one example.

This PR allows the stack allocation to be created at the correct allocation block, and thus remedies such issues.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D121061

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[OMPIRBuilder] Generate aggregate argument for parallel region outlined functions

Summary:
This patch modifies code generation in OpenMPIRBuilder to pass arguments
to the parallel region outlined fu

[OMPIRBuilder] Generate aggregate argument for parallel region outlined functions

Summary:
This patch modifies code generation in OpenMPIRBuilder to pass arguments
to the parallel region outlined function in an aggregate (struct),
besides the global_tid and bound_tid arguments. It depends on the
updated CodeExtractor (see D96854) for support. It mirrors functionality
of Clang codegen (see D102107).

Differential Revision: https://reviews.llvm.org/D110114

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[OpenMP] Overhaul `declare target` handling

This patch fixes various issues with our prior `declare target` handling
and extends it to support `omp begin declare target` as well.

This started with

[OpenMP] Overhaul `declare target` handling

This patch fixes various issues with our prior `declare target` handling
and extends it to support `omp begin declare target` as well.

This started with PR49649 in mind, trying to provide a way for users to
avoid the "ref" global use introduced for globals with internal linkage.
From there it went down the rabbit hole, e.g., all variables, even
`nohost` ones, were emitted into the device code so it was impossible to
determine if "ref" was needed late in the game (based on the name only).
To make it really useful, `begin declare target` was needed as it can
carry the `device_type`. Not emitting variables eagerly had a ripple
effect. Finally, the precedence of the (explicit) declare target list
items needed to be taken into account, that meant we cannot just look
for any declare target attribute to make a decision. This caused the
handling of functions to require fixup as well.

I tried to clean up things while I was at it, e.g., we should not "parse
declarations and defintions" as part of OpenMP parsing, this will always
break at some point. Instead, we keep track what region we are in and
act on definitions and declarations instead, this is what we do for
declare variant and other begin/end directives already.

Highlights:
- new diagnosis for restrictions specificed in the standard,
- delayed emission of globals not mentioned in an explicit
list of a declare target,
- omission of `nohost` globals on the host and `host` globals on the
device,
- no explicit parsing of declarations in-between `omp [begin] declare
variant` and the corresponding end anymore, regular parsing instead,
- precedence for explicit mentions in `declare target` lists over
implicit mentions in the declaration-definition-seq, and
- `omp allocate` declarations will now replace an earlier emitted
global, if necessary.

---

Notes:

The patch is larger than I hoped but it turns out that most changes do
on their own lead to "inconsistent states", which seem less desirable
overall.

After working through this I feel the standard should remove the
explicit declare target forms as the delayed emission is horrible.
That said, while we delay things anyway, it seems to me we check too
often for the current status even though that is often not sufficient to
act upon. There seems to be a lot of duplication that can probably be
trimmed down. Eagerly emitting some things seems pretty weak as an
argument to keep so much logic around.

---

Reviewed By: ABataev

Differential Revision: https://reviews.llvm.org/D101030

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[OpenMP][IRBuilder] Support nested parallel regions

During code generation we might change/add basic blocks so keeping a
list of them is fairly easy to break. Nested parallel regions were
enough. Th

[OpenMP][IRBuilder] Support nested parallel regions

During code generation we might change/add basic blocks so keeping a
list of them is fairly easy to break. Nested parallel regions were
enough. The new scheme does recompute the list of blocks to be outlined
once it is needed.

Reviewed By: anchu-rajendran

Differential Revision: https://reviews.llvm.org/D82722

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