Specifying a kernel with the `ptx_kernel` or `amdgpu_kernel` calling
convention is a more idiomatic and compile-time performant than using
the `nvvm.annoation !"kernel"` metadata.

Transition OMPIRBuilder to use calling conventions for PTX kernels and
no longer emit `nvvm.annoation`. Update OpenMPOpt to work with kernels
specified via calling convention as well as metadata. Update OpenMP
tests to use the calling conventions.

Before we tracked the size of the teams reduction buffer in order to
allocate it at runtime per kernel launch. This patch splits the number
into two parts, the size of the reduction data (=all reduction
variables) and the (maximal) length of the buffer. This will allow us to
allocate less if we need less, e.g., if we have less teams than the
maximal length. It also allows us to move code from clangs codegen into
the runtime as we now know how large the reduction data is.

The KernelEnvironment is for compile time information about a kernel. It
allows the compiler to feed information to the runtime. The
KernelLaunchEnvironment is for dynamic information *per* kernel launch.
It allows the rutime to feed information to the kernel that is not
shared with other invocations of the kernel. The first use case is to
replace the globals that synchronize teams reductions with per-launch
versions. This allows concurrent teams reductions. More uses cases will
follow, e.g., per launch memory pools.

Fixes: https://github.com/llvm/llvm-project/issues/70249

This reverts commit ddbaa11e9f43a38d50d62a9b9b07c3653b6bf8ab.

Reapply the original commit, the broken test was repaired in 5e51363f38d083ab326736c0d4d1b5f9fe0de080 in the meantime.

This reverts commit c2a1249a8257ed033a98e32e425539c6da6700ec.

The MLIR bots are broken with an omp test failure.

The runtime needs to know about the acceptable launch bounds, especially
if the compiler (middle- or backend) assumed those bounds. While this
patch does not yet inform the runtime, it stores the bounds in a place
that can/will be accessed and is associated with the kernel.

This patch introduces per kernel environment. Previously, flags such as execution mode are set through global variables with name like `__kernel_name_exec_mode`. They are accessible on the host by reading the corresponding global variable, but not from the device. Besides, some assumptions, such as no nested parallelism, are not per kernel basis, preventing us applying per kernel optimization in the device runtime.

This is a combination and refinement of patch series D116908, D116909, and D116910.

Depend on D155886.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D142569

This reverts commits for kernel environments as they causes issues in AMD BB.

This patch introduces per kernel environment. Previously, flags such as execution mode are set through global variables with name like `__kernel_name_exec_mode`. They are accessible on the host by reading the corresponding global variable, but not from the device. Besides, some assumptions, such as no nested parallelism, are not per kernel basis, preventing us applying per kernel optimization in the device runtime.

This is a combination and refinement of patch series D116908, D116909, and D116910.

Depend on D155886.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D142569