[clang] [clang] Add builtin_get_vtable_pointer and virtual_member_address (PR #135469)

[Oliver Hunt via cfe-commits]

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@@ -1782,6 +1782,92 @@ static ExprResult PointerAuthStringDiscriminator(Sema &S, CallExpr *Call) {
   return Call;
 }
 
+static ExprResult VirtualMemberAddress(Sema &S, CallExpr *Call) {
+  if (S.checkArgCount(Call, 2))
+    return ExprError();
+
+  for (int i = 0; i < 2; ++i) {
+    ExprResult ArgRValue =
+        S.DefaultFunctionArrayLvalueConversion(Call->getArg(1));
+    if (ArgRValue.isInvalid())
+      return ExprError();
+    Call->setArg(1, ArgRValue.get());
+  }
+
+  if (Call->getArg(0)->isTypeDependent() || Call->getArg(1)->isValueDependent())
+    return Call;
+
+  const Expr *ThisArg = Call->getArg(0);
+  QualType ThisTy = ThisArg->getType();
+  if (ThisTy->isPointerOrReferenceType())
+    ThisTy = ThisTy->getPointeeType();
+  if (!ThisTy->getAsCXXRecordDecl()) {
+    S.Diag(ThisArg->getExprLoc(), diag::err_virtual_member_lhs_cxxrec);
+    return ExprError();
+  }
+
+  const Expr *MemFunArg = Call->getArg(1);
+  APValue Result;
+  if (!MemFunArg->isCXX11ConstantExpr(S.getASTContext(), &Result, nullptr)) {
+    S.Diag(MemFunArg->getExprLoc(), diag::err_virtual_member_addrof);
+    return ExprError();
+  }
+
+  if (!Result.isMemberPointer() ||
+      !isa<CXXMethodDecl>(Result.getMemberPointerDecl())) {
+    S.Diag(MemFunArg->getExprLoc(), diag::err_virtual_member_addrof);
+    return ExprError();
+  }
+
+  const CXXMethodDecl *CXXMethod =
+      cast<CXXMethodDecl>(Result.getMemberPointerDecl());
+  if (!CXXMethod->isVirtual()) {
+    S.Diag(MemFunArg->getExprLoc(), diag::err_virtual_member_addrof);
+    return ExprError();
+  }
+
+  if (ThisTy->getAsCXXRecordDecl() != CXXMethod->getParent() &&
+      !S.IsDerivedFrom(Call->getBeginLoc(), ThisTy,
+                       CXXMethod->getFunctionObjectParameterType())) {
+    S.Diag(ThisArg->getExprLoc(), diag::err_virtual_member_inherit);
+    return ExprError();
+  }
+  return Call;
+}
+
+static ExprResult GetVTablePointer(Sema &S, CallExpr *Call) {
+  if (S.checkArgCount(Call, 1))
+    return ExprError();
+  ExprResult ThisArg = S.DefaultFunctionArrayLvalueConversion(Call->getArg(0));
+  if (ThisArg.isInvalid())
+    return ExprError();
+  Call->setArg(0, ThisArg.get());
+  const Expr *Subject = Call->getArg(0);
+  QualType SubjectType = Subject->getType();
+  if (SubjectType->isPointerOrReferenceType())
----------------
ojhunt wrote:

Will be reverting this to require a pointer arg

https://github.com/llvm/llvm-project/pull/135469