[Clang][CodeGen] `typeid` needs special care when `type_info` is not in the default AS

After https://reviews.llvm.org/D153092, for targets that use a non-default AS for globals, an "interesting" situation arises around typeid and its paired type, type_info:

- on the AST level, the type_info interface is defined with default / generic addresses, be it for function arguments, or for this;
- in IR, type_info values are globals, and thus pointers to type_info values are pointers to global

This leads to a mismatch between the function signature / formal type of the argument, and its actual type. Currently we try to handle such mismatches via `bitcast`, but that is wrong in this case, since an `ascast` is required. This patch ensures that iff the pointer to `type_info` points to a non-default AS, an ascast is inserted so as to match the `typeid` interface / return value type.

Reviewed by: yaxunl

Differential Revision: https://reviews.llvm.org/D157452

1 files changed, 10 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index 4d3f3e9603d9..34d4f37a5d29 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -2195,11 +2195,19 @@ static llvm::Value *EmitTypeidFromVTable(CodeGenFunction &CGF, const Expr *E,
 
 llvm::Value *CodeGenFunction::EmitCXXTypeidExpr(const CXXTypeidExpr *E) {
   llvm::Type *PtrTy = llvm::PointerType::getUnqual(getLLVMContext());
+  LangAS GlobAS = CGM.GetGlobalVarAddressSpace(nullptr);
+
+  auto MaybeASCast = [=](auto &&TypeInfo) {
+    if (GlobAS == LangAS::Default)
+      return TypeInfo;
+    return getTargetHooks().performAddrSpaceCast(CGM,TypeInfo, GlobAS,
+                                                 LangAS::Default, PtrTy);
+  };
 
   if (E->isTypeOperand()) {
     llvm::Constant *TypeInfo =
         CGM.GetAddrOfRTTIDescriptor(E->getTypeOperand(getContext()));
-    return TypeInfo;
+    return MaybeASCast(TypeInfo);
   }
 
   // C++ [expr.typeid]p2:
@@ -2212,7 +2220,7 @@ llvm::Value *CodeGenFunction::EmitCXXTypeidExpr(const CXXTypeidExpr *E) {
     return EmitTypeidFromVTable(*this, E->getExprOperand(), PtrTy);
 
   QualType OperandTy = E->getExprOperand()->getType();
-  return CGM.GetAddrOfRTTIDescriptor(OperandTy);
+  return MaybeASCast(CGM.GetAddrOfRTTIDescriptor(OperandTy));
 }
 
 static llvm::Value *EmitDynamicCastToNull(CodeGenFunction &CGF,