[clang] [clang] Allow devirtualisation of indirect calls to final virtual methods (PR #165341)

[Oliver Hunt via cfe-commits]

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@@ -1316,7 +1316,17 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
       // fast register allocator would be happier...
       CXXThisValue = CXXABIThisValue;
     }
-
+    if (CGM.getCodeGenOpts().StrictVTablePointers) {
+      const CXXRecordDecl *ThisRecordDecl = MD->getParent();
+      bool IsPolymorphicObject = ThisRecordDecl->isPolymorphic();
+      bool IsStructor = isa<CXXDestructorDecl, CXXConstructorDecl>(MD);
+      bool IsFinal = ThisRecordDecl->isEffectivelyFinal();
+      // We do not care about whether this is a virtual method, because even
+      // if the current method is not virtual, it may be calling another method
+      // that calls a virtual function.
+      if (IsPolymorphicObject && !IsStructor && IsFinal)
+        EmitVTableAssumptionLoads(ThisRecordDecl, LoadCXXThisAddress());
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ojhunt wrote:

good call, will do, and virtual inheritance

https://github.com/llvm/llvm-project/pull/165341