[PGO][OpenMP] Instrumentation for GPU devices (#76587)

This pull request is the first part of an ongoing effort to extends PGO
instrumentation to GPU device code. This PR makes the following changes:

- Adds blank registration functions to device RTL
- Gives PGO globals protected visibility when targeting a supported GPU
- Handles any addrspace casts for PGO calls
- Implements PGO global extraction in GPU plugins (currently only dumps
info)

These changes can be tested by supplying `-fprofile-instrument=clang`
while targeting a GPU.

1 files changed, 22 insertions, 0 deletions

diff --git a/offload/DeviceRTL/src/Profiling.cpp b/offload/DeviceRTL/src/Profiling.cpp
new file mode 100644
index 000000000000..bb3caaadcc03
--- /dev/null
+++ b/offload/DeviceRTL/src/Profiling.cpp
@@ -0,0 +1,22 @@
+//===------- Profiling.cpp ---------------------------------------- C++ ---===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "Profiling.h"
+
+#pragma omp begin declare target device_type(nohost)
+
+extern "C" {
+
+// Provides empty implementations for certain functions in compiler-rt
+// that are emitted by the PGO instrumentation.
+void __llvm_profile_register_function(void *Ptr) {}
+void __llvm_profile_register_names_function(void *Ptr, long int I) {}
+void __llvm_profile_instrument_memop(long int I, void *Ptr, int I2) {}
+}
+
+#pragma omp end declare target