[llvm] [OpenMP][Offload] Update the Logic for Configuring Auto Zero-Copy (PR #143638)

[via llvm-commits]

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@@ -286,16 +286,16 @@ void PluginManager::registerLib(__tgt_bin_desc *Desc) {
   }
   PM->RTLsMtx.unlock();
 
-  bool UseAutoZeroCopy = Plugins.size() > 0;
+  bool UseAutoZeroCopy = false;
 
   auto ExclusiveDevicesAccessor = getExclusiveDevicesAccessor();
-  for (const auto &Device : *ExclusiveDevicesAccessor)
-    UseAutoZeroCopy &= Device->useAutoZeroCopy();
+  // APUs are homogeneous set of GPUs. Check the first device for
+  // configuring Auto Zero-Copy.
+  if (ExclusiveDevicesAccessor->size() > 0) {
+    auto &Device = *(*ExclusiveDevicesAccessor)[0];
+    UseAutoZeroCopy = Device.useAutoZeroCopy();
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Kewen12 wrote:

>we do not have a case where one of the devices is an APU and the others could be something else. You could build it yourself perhaps, but it doesn't exist today as a product. If time comes when there will be such a case, we can revisit this.

We could have a system with mix of GPUs in theory, but we didn't see that in product in real life. Perhaps we will see a produce of that design in the future :) We could make update accordingly when it happens. Thanks for the comments!

https://github.com/llvm/llvm-project/pull/143638