[CodeGen][ObjC] Fix assert on calling __builtin_constant_p with Obj…

…C 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

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);

clang/test/CodeGenObjC/builtin-constant-p.m

@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -O3 -disable-llvm-passes -o - %s | FileCheck %s
+
+// Test that can call `__builtin_constant_p` with instances of different
+// Objective-C classes.
+// rdar://problem/47499250
+@class Foo;
+@class Bar;
+
+extern void callee(void);
+
+// CHECK-LABEL: define void @test(%0* %foo, %1* %bar)
+void test(Foo *foo, Bar *bar) {
+  // CHECK: [[ADDR_FOO:%.*]] = bitcast %0* %{{.*}} to i8*
+  // CHECK-NEXT: call i1 @llvm.is.constant.p0i8(i8* [[ADDR_FOO]])
+  // CHECK: [[ADDR_BAR:%.*]] = bitcast %1* %{{.*}} to i8*
+  // CHECK-NEXT: call i1 @llvm.is.constant.p0i8(i8* [[ADDR_BAR]])
+  if (__builtin_constant_p(foo) && __builtin_constant_p(bar))
+    callee();
+}
+
+// Test other Objective-C types.
+// CHECK-LABEL: define void @test_more(i8* %object, i8* %klass)
+void test_more(id object, Class klass) {
+  // CHECK: call i1 @llvm.is.constant.p0i8(i8* %{{.*}})
+  // CHECK: call i1 @llvm.is.constant.p0i8(i8* %{{.*}})
+  if (__builtin_constant_p(object) && __builtin_constant_p(klass))
+    callee();
+}