[clang] [PAC] Implement authentication for C++ member function pointers (PR #99576)

[Daniil Kovalev via cfe-commits]

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@@ -5877,119 +5882,130 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
   CallArgs.freeArgumentMemory(*this);
 
   // Extract the return value.
-  RValue Ret = [&] {
-    switch (RetAI.getKind()) {
-    case ABIArgInfo::CoerceAndExpand: {
-      auto coercionType = RetAI.getCoerceAndExpandType();
-
-      Address addr = SRetPtr.withElementType(coercionType);
-
-      assert(CI->getType() == RetAI.getUnpaddedCoerceAndExpandType());
-      bool requiresExtract = isa<llvm::StructType>(CI->getType());
+  RValue Ret;
 
-      unsigned unpaddedIndex = 0;
-      for (unsigned i = 0, e = coercionType->getNumElements(); i != e; ++i) {
-        llvm::Type *eltType = coercionType->getElementType(i);
-        if (ABIArgInfo::isPaddingForCoerceAndExpand(eltType)) continue;
-        Address eltAddr = Builder.CreateStructGEP(addr, i);
-        llvm::Value *elt = CI;
-        if (requiresExtract)
-          elt = Builder.CreateExtractValue(elt, unpaddedIndex++);
-        else
-          assert(unpaddedIndex == 0);
-        Builder.CreateStore(elt, eltAddr);
+  // If the current function is a virtual function pointer thunk, avoid copying
+  // the return value of the musttail call to a temporary.
+  if (IsVirtualFunctionPointerThunk)
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kovdan01 wrote:

Nit: it's probably worth adding braces since else branch is long (while still being one statement).

https://github.com/llvm/llvm-project/pull/99576