[c++20] Add CXXRewrittenBinaryOperator to represent a comparison
operator that is rewritten as a call to multiple other operators.

No functionality change yet: nothing creates these expressions.

llvm-svn: 375305
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 2bd1b0b..dcd365c 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -1267,6 +1267,8 @@
   case Expr::CXXOperatorCallExprClass:
   case Expr::UserDefinedLiteralClass:
     return EmitCallExprLValue(cast<CallExpr>(E));
+  case Expr::CXXRewrittenBinaryOperatorClass:
+    return EmitLValue(cast<CXXRewrittenBinaryOperator>(E)->getSemanticForm());
   case Expr::VAArgExprClass:
     return EmitVAArgExprLValue(cast<VAArgExpr>(E));
   case Expr::DeclRefExprClass: