Revert "[OpenMP] Remove noinline attributes in the device runtime"

The behaviour of this patch is not great, but it has some side-effects
that are required for OpenMPOpt to work. The problem is that

Revert "[OpenMP] Remove noinline attributes in the device runtime"

The behaviour of this patch is not great, but it has some side-effects
that are required for OpenMPOpt to work. The problem is that when we use
`-mlink-builtin-bitcode` we only import used symbols from the runtime.
Then OpenMPOpt will insert calls to symbols that were not previously
included. This patch removed this implicit behaviour as these functions
were kept alive by the `noinline` simply because it kept calls to them
in the module. This caused regression in some tests that relied on some
OpenMPOpt passes without using LTO. Reverting for the LLVM15 release but
will try to fix it more correctly on main.

This reverts commit d61d72dae604c3258e25c00622b1a85861450303.

Fixes #56752

(cherry picked from commit b08369f7f288b6efb0897953da42ed54e60cfc0b)

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[OpenMP] Remove noinline attributes in the device runtime

We previously used the `noinline` attributes to specify some defintions
which should be kept alive in the runtime. These were then stripped

[OpenMP] Remove noinline attributes in the device runtime

We previously used the `noinline` attributes to specify some defintions
which should be kept alive in the runtime. These were then stripped
immediately in the OpenMPOpt module pass. However, Since the changes in
D130298, we not explicitly state which functions will have external
visiblity in the bitcode library. Additionally the OpenMPOpt module pass
should run before the inliner pass, so this shouldn't make a difference
in whether or not the functions will be alive for the initial pass of
OpenMPOpt. This should simplify the interface, and additionally save
time spend on scanning funciton names for noinline.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D130368

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[Libomptarget] Do not use retaining attributes for the static library

When we build the libomptarget device runtime library targeting bitcode,
we need special care to make sure that certain function

[Libomptarget] Do not use retaining attributes for the static library

When we build the libomptarget device runtime library targeting bitcode,
we need special care to make sure that certain functions are not
optimized out. This is because we manually internalize and optimize
these definitions, ignoring their standard linkage semantics. When we
build with the static library, we can maintain these semantics and we do
not need these to be kept-alive. Furthermore, if they are kept-alive it
prevents them from being removed during LTO. This prevents us from
completely internalizing `IsSPMDMode` and removing several other
functions. This patch removes these for the static library target by
using a macro definition to enable them.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D126701

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[Libomptarget] Address existing warnings in the device runtime library

This patche attemps to address the current warnings in the OpenMP
offloading device runtime. Previously we did not see these be

[Libomptarget] Address existing warnings in the device runtime library

This patche attemps to address the current warnings in the OpenMP
offloading device runtime. Previously we did not see these because we
compiled the runtime without the standard warning flags enabled.
However, these warnings are used when we now build the static library
version of this runtime. This became extremely noisy when coupled with
the fact the we compile each file roughly 32 times when all the
architectures are considered. So it would be ideal to not have all these
warnings show up when building.

Most of these errors were simply implicit switch-case fallthroughs,
which can be addressed using C++17's fallthrough attribute. Additionally
there was a volatile variable that was being casted away. This is most
likely safe to remove because we cast it away before its even used and
didn't seem to affect anything in testing.

Depends on D125260

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D125339

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[Libomptarget] Allow the device runtime to be compiled for the host

Currently the OpenMP offloading device runtime is only expected to be
compiled for the specific architecture it's targeting. This

[Libomptarget] Allow the device runtime to be compiled for the host

Currently the OpenMP offloading device runtime is only expected to be
compiled for the specific architecture it's targeting. This is
problematic if we want to make compiling the device runtime more general
via the standar `clang` driver rather than invoking the clang front-end
directly. This patch addresses this by primarily changing the declare
type to `nohost` so the host will not contain any of this code.
Additionally we forward declare the functions that are defined via
variants, otherwise these would cause problems on the host.

Reviewed By: jdoerfert, tianshilei1992

Differential Revision: https://reviews.llvm.org/D125260

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[Libomptarget] Work around bug in initialization of libomptarget

Libomptarget uses some shared variables to track certain internal stated
in the runtime. This causes problems when we have code that

[Libomptarget] Work around bug in initialization of libomptarget

Libomptarget uses some shared variables to track certain internal stated
in the runtime. This causes problems when we have code that contains no
OpenMP kernels. These variables are normally initialized upon kernel
entry, but if there are no kernels we will see no initialization.
Currently we load the runtime into each source file when not running in
LTO mode, so these variables will be erroneously considered undefined or
dead and removed, causing miscompiles. This patch temporarily works
around the most obvious case, but others still exhibit this problem. We
will need to fix this more soundly later.

Fixes #54208.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D121007

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[OpenMP][FIX] Eliminate race on the IsSPMD global

The `IsSPMD` global can only be read by threads other than the main
thread *after* initialization is complete. To allow usage of
`mapping::getBlockS

[OpenMP][FIX] Eliminate race on the IsSPMD global

The `IsSPMD` global can only be read by threads other than the main
thread *after* initialization is complete. To allow usage of
`mapping::getBlockSize` before initialization is done, we can pass the
`IsSPMD` state explicitly. This is similar to other APIs that take
`IsSPMD` explicitly to avoid such a race, e.g.,
`mapping::isInitialThreadInLevel0(IsSPMD)`

Fixes https://github.com/llvm/llvm-project/issues/53857

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[Libomptarget][NFC] Remove constexpr to hide warnings

Currently whenever we compile the device runtime we get the following
'Mapping.cpp:32:32: warning: inline function '_OMP::impl::getGridValue'
is

[Libomptarget][NFC] Remove constexpr to hide warnings

Currently whenever we compile the device runtime we get the following
'Mapping.cpp:32:32: warning: inline function '_OMP::impl::getGridValue'
is not defined [-Wundefined-inline]' warning. This can be silenced by
removing the constexpr attribute for this function. Doing this doesn't
change the generated bitcode at all but prevents the screen from getting
filled with warnings whenver we build the runtime.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D119747

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[clang][openmp][NFC] Remove arch-specific CGOpenMPRuntimeGPU files

The existing CGOpenMPRuntimeAMDGCN and CGOpenMPRuntimeNVPTX classes are
just code bloat. By removing them, the codebase gets a bit

[clang][openmp][NFC] Remove arch-specific CGOpenMPRuntimeGPU files

The existing CGOpenMPRuntimeAMDGCN and CGOpenMPRuntimeNVPTX classes are
just code bloat. By removing them, the codebase gets a bit cleaner.

Reviewed By: jdoerfert, JonChesterfield, tianshilei1992

Differential Revision: https://reviews.llvm.org/D113421

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Revert "[clang][openmp][NFC] Remove arch-specific CGOpenMPRuntimeGPU files"

This reverts commit 81a7cad2ffc18f15b732f69d991c8398c979c5ca.

[clang][openmp][NFC] Remove arch-specific CGOpenMPRuntimeGPU files

The existing CGOpenMPRuntimeAMDGCN and CGOpenMPRuntimeNVPTX classes are
just code bloat. By removing them, the codebase gets a bit

[clang][openmp][NFC] Remove arch-specific CGOpenMPRuntimeGPU files

The existing CGOpenMPRuntimeAMDGCN and CGOpenMPRuntimeNVPTX classes are
just code bloat. By removing them, the codebase gets a bit cleaner.

Reviewed By: jdoerfert, JonChesterfield, tianshilei1992

Differential Revision: https://reviews.llvm.org/D113421

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[OpenMP][NFCI] Cleanup new device RT mapping interface

Minimize the `impl` interface and clean up some uses of mapping
functions.

Reviewed By: jhuber6

Differential Revision: https://reviews.llvm.o

[OpenMP][NFCI] Cleanup new device RT mapping interface

Minimize the `impl` interface and clean up some uses of mapping
functions.

Reviewed By: jhuber6

Differential Revision: https://reviews.llvm.org/D112154

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[OpenMP][FIX] Avoid a race between initialization and first state reads

When we pick state 0 to initialize state but thread N is going to be the
"main thread", in generic mode, we would require extr

[OpenMP][FIX] Avoid a race between initialization and first state reads

When we pick state 0 to initialize state but thread N is going to be the
"main thread", in generic mode, we would require extra synchronization.
Instead, we should pick the main thread to initialize state in generic
mode and any thread in SPMD mode.

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D112874

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[OpenMP] Use function tracing RAII for runtime functions.

This patch adds support for using function tracing features to track the
executino of runtime functions in the device runtime library. This

[OpenMP] Use function tracing RAII for runtime functions.

This patch adds support for using function tracing features to track the
executino of runtime functions in the device runtime library. This is
enabled by first compiling the new runtime with
`-fopenmp-target-debug=3` and running with
`LIBOMPTARGET_DEVICE_RTL_DEBUG=3`. The output only tracks team 0 and
thread 0 so there isn't much output when using a generic region.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D112002

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[libomptarget] Refactor DeviceRTL prior to AMDGPU bringup

Subset of D111993. Fix typos, rename read to load.

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D111999

[OpenMP] Add RTL function for getting number of threads in block.

This patch adds support for the
`__kmpc_get_hardware_num_threads_in_block` function that returns the
number of threads. This was mis

[OpenMP] Add RTL function for getting number of threads in block.

This patch adds support for the
`__kmpc_get_hardware_num_threads_in_block` function that returns the
number of threads. This was missing in the new runtime and was used by
the AMDGPU plugin which prevented it from using the new runtime. This
patchs also unified the interface for getting the thread numbers in the
frontend.

Originally authored by jdoerfert.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D111475

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[OpenMP] Avoid calling `isSPMDMode` during RT initialization

Until we hit the first barrier we should not call `mapping::isSPMDMode`
with all threads. Instead, we now have (and use during initializa

[OpenMP] Avoid calling `isSPMDMode` during RT initialization

Until we hit the first barrier we should not call `mapping::isSPMDMode`
with all threads. Instead, we now have (and use during initialization) a
`mapping::isMainThreadInGenericMode` overload that takes the known
SPMD-mode state and one that queries it.

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D111381

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[OpenMP] Fix KeepAlive usage

Summary:
Functions were called the wrong way around, this didn't keep the symbol
alive.

[OpenMP] Make sure the Thread ID function is not removed

Summary:
The thread ID function was reintroduced in D110195, but could
potentially be removed by the optimizer. Make the function noinline to

[OpenMP] Make sure the Thread ID function is not removed

Summary:
The thread ID function was reintroduced in D110195, but could
potentially be removed by the optimizer. Make the function noinline to
preserve the call sites and add it to the externalization RAII so its
definition is not removed by the attributor.

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[OpenMP] Add thread ID function into new RTL

The new device runtime library currently lacks the
`kmpc_get_hardware_thread_id_in_block` function which is currently used
when doing the SPMDzation opti

[OpenMP] Add thread ID function into new RTL

The new device runtime library currently lacks the
`kmpc_get_hardware_thread_id_in_block` function which is currently used
when doing the SPMDzation optimization. This call would be introduced
through the optimization and then cause a linking error because it was
not present. This patch adds support for this runtime call.

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D110195

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[openmp] Use llvm GridValues from devicertl

Add include path to the cmakefiles and set the target_impl enums
from the llvm constants instead of copying the values.

Reviewed By: jdoerfert

Different

[openmp] Use llvm GridValues from devicertl

Add include path to the cmakefiles and set the target_impl enums
from the llvm constants instead of copying the values.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D108391

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[OpenMP] Prototype opt-in new GPU device RTL

The "old" OpenMP GPU device runtime (D14254) has served us well for many
years but modernizing it has caused some pain recently. This patch
introduces an

[OpenMP] Prototype opt-in new GPU device RTL

The "old" OpenMP GPU device runtime (D14254) has served us well for many
years but modernizing it has caused some pain recently. This patch
introduces an alternative which is mostly written from scratch embracing
OpenMP 5.X, C++, LLVM coding style (where applicable), and conceptual
interfaces. This new runtime is opt-in through a clang flag (D106793).
The new runtime is currently only build for nvptx and has "-new" in its
name.

The design is tailored towards middle-end optimizations rather than
front-end code generation choices, a trend we already started in the old
runtime a while back. In contrast to the old one, state is organized in
a simple manner rather than a "smart" one. While this can induce costs
it helps optimizations. Our expectation is that the majority of codes
can be optimized and a "simple" design is therefore preferable. The new
runtime does also avoid users to pay for things they do not use,
especially wrt. memory. The unlikely case of nested parallelism is
supported but costly to make the more likely case use less resources.

The worksharing and reduction implementation have been taken from the
old runtime and will be rewritten in the future if necessary.

Documentation and debug features are still mostly missing and will be
added over time.

All external symbols start with `__kmpc` for legacy reasons but should
be renamed once we switch over to a single runtime. All internal symbols
are placed in appropriate namespaces (anonymous or `_OMP`) to avoid name
clashes with user symbols.

Differential Revision: https://reviews.llvm.org/D106803

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