Refactor constant evaluation of typeid(T) to track a symbolic type_info

object rather than tracking the originating expression.

This is groundwork for supporting polymorphic typeid expressions. (Note
that this somewhat regresses our support for DR1968, but it turns out
that that never actually worked anyway, at least in non-trivial cases.)

This reinstates r360974, reverted in r360988, with a fix for a
static_assert failure on 32-bit builds: force Type base class to have
8-byte alignment like the rest of Clang's AST nodes.

llvm-svn: 360995

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index dd71cf02d95..70904b192a3 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -1735,6 +1735,17 @@ ConstantLValueEmitter::tryEmitBase(const APValue::LValueBase &base) {
     return nullptr;
   }
 
+  // Handle typeid(T).
+  if (TypeInfoLValue TI = base.dyn_cast<TypeInfoLValue>()) {
+    llvm::Type *StdTypeInfoPtrTy =
+        CGM.getTypes().ConvertType(base.getTypeInfoType())->getPointerTo();
+    llvm::Constant *TypeInfo =
+        CGM.GetAddrOfRTTIDescriptor(QualType(TI.getType(), 0));
+    if (TypeInfo->getType() != StdTypeInfoPtrTy)
+      TypeInfo = llvm::ConstantExpr::getBitCast(TypeInfo, StdTypeInfoPtrTy);
+    return TypeInfo;
+  }
+
   // Otherwise, it must be an expression.
   return Visit(base.get<const Expr*>());
 }