[CodeGen][ObjC] Fix assert on calling `__builtin_constant_p` with ObjC objects.

When we are calling `__builtin_constant_p` with ObjC objects of
different classes, we hit the assertion

> Assertion failed: (isa<X>(Val) && "cast<Ty>() argument of incompatible type!"), function cast, file include/llvm/Support/Casting.h, line 254.

It happens because LLVM types for `ObjCInterfaceType` are opaque and
have no name (see `CodeGenTypes::ConvertType`). As the result, for
different ObjC classes we have different `is_constant` intrinsics with
the same name `llvm.is.constant.p0s_s`. When we try to reuse an
intrinsic with the same name, we fail because of type mismatch.

Fix by bitcasting `ObjCObjectPointerType` to `id` prior to passing as an
argument to `__builtin_constant_p`. This results in using intrinsic
`llvm.is.constant.p0i8` and correct types.

rdar://problem/47499250

Reviewers: rjmccall, ahatanak, void

Reviewed By: void, ahatanak

Subscribers: ddunbar, jkorous, hans, dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D57427

llvm-svn: 353577

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 68d27311d33..5448ac1b206 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -1982,6 +1982,12 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
       return RValue::get(ConstantInt::get(ResultType, 0));
 
     Value *ArgValue = EmitScalarExpr(Arg);
+    if (ArgType->isObjCObjectPointerType()) {
+      // Convert Objective-C objects to id because we cannot distinguish between
+      // LLVM types for Obj-C classes as they are opaque.
+      ArgType = CGM.getContext().getObjCIdType();
+      ArgValue = Builder.CreateBitCast(ArgValue, ConvertType(ArgType));
+    }
     Function *F =
         CGM.getIntrinsic(Intrinsic::is_constant, ConvertType(ArgType));
     Value *Result = Builder.CreateCall(F, ArgValue);