Force a load when creating a reference to a temporary copied from a bitfield.

For this source:
  const int &ref = someStruct.bitfield;

We used to generate this AST:

  DeclStmt [...]
  `-VarDecl [...] ref 'const int &'
    `-MaterializeTemporaryExpr [...] 'const int' lvalue
      `-ImplicitCastExpr [...] 'const int' lvalue <NoOp>
        `-MemberExpr [...] 'int' lvalue bitfield .bitfield [...]
          `-DeclRefExpr [...] 'struct X' lvalue ParmVar [...] 'someStruct' 'struct X'

Notice the lvalue inside the MaterializeTemporaryExpr, which is very
confusing (and caused an assertion to fire in the analyzer - PR15694).

We now generate this:

  DeclStmt [...]
  `-VarDecl [...] ref 'const int &'
    `-MaterializeTemporaryExpr [...] 'const int' lvalue
      `-ImplicitCastExpr [...] 'int' <LValueToRValue>
        `-MemberExpr [...] 'int' lvalue bitfield .bitfield [...]
          `-DeclRefExpr [...] 'struct X' lvalue ParmVar [...] 'someStruct' 'struct X'

Which makes a lot more sense. This allows us to remove code in both
CodeGen and AST that hacked around this special case.

The commit also makes Clang accept this (legal) C++11 code:

  int &&ref = std::move(someStruct).bitfield

PR15694 / <rdar://problem/13600396>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179250 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 0 deletions

diff --git a/include/clang/Sema/Initialization.h b/include/clang/Sema/Initialization.h
index 8459be16f4..9740318e02 100644
--- a/include/clang/Sema/Initialization.h
+++ b/include/clang/Sema/Initialization.h
@@ -594,6 +594,8 @@ public:
     SK_QualificationConversionXValue,
     /// \brief Perform a qualification conversion, producing an lvalue.
     SK_QualificationConversionLValue,
+    /// \brief Perform a load from a glvalue, producing an rvalue.
+    SK_LValueToRValue,
     /// \brief Perform an implicit conversion sequence.
     SK_ConversionSequence,
     /// \brief Perform list-initialization without a constructor
@@ -911,6 +913,12 @@ public:
   void AddQualificationConversionStep(QualType Ty,
                                      ExprValueKind Category);
   
+  /// \brief Add a new step that performs a load of the given type.
+  ///
+  /// Although the term "LValueToRValue" is conventional, this applies to both
+  /// lvalues and xvalues.
+  void AddLValueToRValueStep(QualType Ty);
+
   /// \brief Add a new step that applies an implicit conversion sequence.
   void AddConversionSequenceStep(const ImplicitConversionSequence &ICS,
                                  QualType T);