[OpenMP] Avoid emitting maps for target link variables when unified memory is used

[gtbercea]

Summary

This patch avoids the emission of maps for target link variables when unified memory is present.

[ABataev]

lib/CodeGen/CGOpenMPRuntime.cpp

8259

Hmm, what about regular declare target declarations? Also, this is not enough. You also should not capture such variables in the captured regions.

[gtbercea]

• Fix function call.

[gtbercea]

lib/CodeGen/CGOpenMPRuntime.cpp

8259

For now, only variables under the link clause are considered for unified memory usage.

[gtbercea]

• Include sema check.

[ABataev]

Tests?

lib/CodeGen/CGOpenMPRuntime.h

1628

Do we need to make it virtual?

[gtbercea]

• Add test.

[ABataev]

Just one question after looking at the test: how we're going to link the device variable to its host copy? I think the address should be passed to the runtime, no?

lib/CodeGen/CGOpenMPRuntime.h

1628

Still not answered

[gtbercea]

In D60883#1516693, @ABataev wrote:

Just one question after looking at the test: how we're going to link the device variable to its host copy? I think the address should be passed to the runtime, no?

The runtime will take care of it by performing a copy of the host address into the device pointer.

[gtbercea]

• Remove virtual.

[ABataev]

lib/CodeGen/CGOpenMPRuntime.h

1628

You can make this function const.

[gtbercea]

• Make function const.

lib/CodeGen/CGOpenMPRuntime.h

public:
   /// Perform check on requires decl to ensure that target architecture
   /// supports unified addressing
   virtual void checkArchForUnifiedAddressing(const OMPRequiresDecl *D);
 
   /// Checks if the variable has associated OMPAllocateDeclAttr attribute with
   /// the predefined allocator and translates it into the corresponding address
   /// space.
   virtual bool hasAllocateAttributeForGlobalVar(const VarDecl *VD, LangAS &AS);
+
+  /// Return whether the unified_shared_memory has been specified.
+  virtual bool hasRequiresUnifiedSharedMemory();
 };
 
 /// Class supports emissionof SIMD-only code.
 class CGOpenMPSIMDRuntime final : public CGOpenMPRuntime {
 public:
   explicit CGOpenMPSIMDRuntime(CodeGenModule &CGM) : CGOpenMPRuntime(CGM) {}
   ~CGOpenMPSIMDRuntime() override {}
 

lib/CodeGen/CGOpenMPRuntime.cpp

public:
   }
 
   /// Generate the base pointers, section pointers, sizes and map types
   /// associated with the declare target link variables.
   void generateInfoForDeclareTargetLink(MapBaseValuesArrayTy &BasePointers,
                                         MapValuesArrayTy &Pointers,
                                         MapValuesArrayTy &Sizes,
                                         MapFlagsArrayTy &Types) const {
+    // If using unified memory, no need to do the mappings.
+    if (CGF.CGM.getOpenMPRuntime().hasRequiresUnifiedSharedMemory())
+      return;
+
     // Map other list items in the map clause which are not captured variables
     // but "declare target link" global variables.
     for (const auto *C : this->CurDir.getClausesOfKind<OMPMapClause>()) {
       for (const auto &L : C->component_lists()) {
         if (!L.first)
           continue;
         const auto *VD = dyn_cast<VarDecl>(L.first);
         if (!VD)
case OMPAllocateDeclAttr::OMPPTeamMemAlloc:
     return true;
   case OMPAllocateDeclAttr::OMPUserDefinedMemAlloc:
     llvm_unreachable("Expected predefined allocator for the variables with the "
                      "static storage.");
   }
   return false;
 }
 
+bool CGOpenMPRuntime::hasRequiresUnifiedSharedMemory() {
+  return HasRequiresUnifiedSharedMemory;
+}
+
 CGOpenMPRuntime::DisableAutoDeclareTargetRAII::DisableAutoDeclareTargetRAII(
     CodeGenModule &CGM)
     : CGM(CGM) {
   if (CGM.getLangOpts().OpenMPIsDevice) {
     SavedShouldMarkAsGlobal = CGM.getOpenMPRuntime().ShouldMarkAsGlobal;
     CGM.getOpenMPRuntime().ShouldMarkAsGlobal = false;
   }
 }