[OpenMPOpt] Initialize OpenMPIRBuilderConfig::IsGPU flag

[skatrak]

This patch ensures the IsGPU flag is set by the OpenMPOpt pass, so that it can be relied upon by OpenMPIRBuilder methods when called by that pass as well.

Since currently there are very limited callers for the OpenMPIRBuilder::isGPU() method, no assertions are being triggered by the lack of initialization of this flag. However, when more offloading-related features are implemented, it will eventually start happening.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Sergio Afonso (skatrak)

Changes

This patch ensures the IsGPU flag is set by the OpenMPOpt pass, so that it can be relied upon by OpenMPIRBuilder methods when called by that pass as well.

Since currently there are very limited callers for the OpenMPIRBuilder::isGPU() method, no assertions are being triggered by the lack of initialization of this flag. However, when more offloading-related features are implemented, it will eventually start happening.

---

Full diff: https://github.com/llvm/llvm-project/pull/104456.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/IPO/OpenMPOpt.cpp (+13)

diff --git a/llvm/lib/Transforms/IPO/OpenMPOpt.cpp b/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
index 798bcb77328fc..8c2e8e5039510 100644
--- a/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
+++ b/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
@@ -286,6 +286,19 @@ struct OMPInformationCache : public InformationCache {
         OpenMPPostLink(OpenMPPostLink) {
 
     OMPBuilder.Config.IsTargetDevice = isOpenMPDevice(OMPBuilder.M);
+    const Triple T(OMPBuilder.M.getTargetTriple());
+    switch (T.getArch()) {
+    case llvm::Triple::nvptx:
+    case llvm::Triple::nvptx64:
+    case llvm::Triple::amdgcn:
+      assert(OMPBuilder.Config.IsTargetDevice &&
+             "OpenMP AMDGPU/NVPTX is only prepared to deal with device code.");
+      OMPBuilder.Config.IsGPU = true;
+      break;
+    default:
+      OMPBuilder.Config.IsGPU = false;
+      break;
+    }
     OMPBuilder.initialize();
     initializeRuntimeFunctions(M);
     initializeInternalControlVars();

[shiltian]

The change is fine but I wonder in what cases the assertion can be triggered.

[skatrak]

The change is fine but I wonder in what cases the assertion can be triggered.

Thank you @shiltian for giving this a look. At the moment it would be difficult (maybe impossible?) to trigger, since OpenMPIRBuilder::isGPU() is barely called at all. We do have downstream features (which we plan on upstreaming hopefully soon) that introduce more uses of that flag within the OMPIRBuilder, and those do trigger the assertion if it's not initialized by the OpenMPOpt pass.

Even if the assert doesn't currently trigger, I think it's worth making sure this property is initialized since it's a bit of a hidden bug.

[skatrak]

Ping for review!