Introduce a new cast kind for an "lvalue bitcast", which handles

reinterpret_casts (possibly indirectly via C-style/functional casts)
on values, e.g., 

  int i;
  reinterpret_cast<short&>(i);

The IR generated for this is essentially the same as for

  *reinterpret_cast<short*>(&i).

Fixes PR6437, PR7593, and PR7344. 

llvm-svn: 108294

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 1ebc2c571a0..ef38209e1ea 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -925,6 +925,15 @@ Value *ScalarExprEmitter::EmitCastExpr(CastExpr *CE) {
     //assert(0 && "Unknown cast kind!");
     break;
 
+  case CastExpr::CK_LValueBitCast: {
+    Value *V = EmitLValue(E).getAddress();
+    V = Builder.CreateBitCast(V, 
+                          ConvertType(CGF.getContext().getPointerType(DestTy)));
+    // FIXME: Are the qualifiers correct here?
+    return EmitLoadOfLValue(LValue::MakeAddr(V, CGF.MakeQualifiers(DestTy)), 
+                            DestTy);
+  }
+      
   case CastExpr::CK_AnyPointerToObjCPointerCast:
   case CastExpr::CK_AnyPointerToBlockPointerCast:
   case CastExpr::CK_BitCast: {