[clang] [llvm] [OpenMP] Adds omp_target_is_accessible routine (PR #138294)

[Nicole Aschenbrenner via cfe-commits]

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@@ -196,6 +196,34 @@ EXTERN int omp_target_is_present(const void *Ptr, int DeviceNum) {
   return Rc;
 }
 
+/// Check whether a pointer is accessible from a device.
+/// Returns true when accessibility is guaranteed otherwise returns false.
+EXTERN int omp_target_is_accessible(const void *Ptr, size_t Size,
+                                    int DeviceNum) {
+  TIMESCOPE();
+  OMPT_IF_BUILT(ReturnAddressSetterRAII RA(__builtin_return_address(0)));
+  DP("Call to omp_target_is_accessible for device %d, address " DPxMOD
+     ", size %zu\n",
+     DeviceNum, DPxPTR(Ptr), Size);
+
+  if (!Ptr) {
+    DP("Call to omp_target_is_accessible with NULL ptr returning false\n");
+    return false;
+  }
+
+  if (DeviceNum == omp_get_initial_device() || DeviceNum == -1) {
+    DP("Call to omp_target_is_accessible on host, returning true\n");
+    return true;
+  }
+
+  // The device number must refer to a valid device
+  auto DeviceOrErr = PM->getDevice(DeviceNum);
+  if (!DeviceOrErr)
+    FATAL_MESSAGE(DeviceNum, "%s", toString(DeviceOrErr.takeError()).c_str());
----------------
nicebert wrote:

I can make this change but then we probably need to reconsider how we handle invalid devices in all cases in the runtime since in the API.cpp file alone it's handled in this way for:
is_present
memcpy
(dis)associate_ptr
get_mapped_ptr

https://github.com/llvm/llvm-project/pull/138294