[Verifier] Assert gc_relocate always return a pointer type

[• chenli]

Summary

Add an assertion in verifier.cpp to make sure gc_relocate relocate a gc pointer, and its return type has the same address space with the relocated pointer.

[sanjoy]

I think we should assert that the address spaces of the source and destination pointers match. Also, please add a test case.

[pgavlin]

+1 to Sanjoy's comments. Thanks for doing this.

[• chenli]

Add an assert for address space and testcase.

[pgavlin]

Please add a test case for the first assert as well (i.e. a case where relocate is returning a non-pointer type).

[• chenli]

In D9695#172229, @pgavlin wrote:

Please add a test case for the first assert as well (i.e. a case where relocate is returning a non-pointer type).

Will do it now

[• chenli]

In D9695#172229, @pgavlin wrote:

Please add a test case for the first assert as well (i.e. a case where relocate is returning a non-pointer type).

Hi Pat,

After some digging, I found that the first assert is actually unnecessary.
gc_relocate is defined to return a pointer type in intrinsics.td:

def int_experimental_gc_relocate : Intrinsic<[llvm_anyptr_ty],
                                [llvm_i32_ty, llvm_i32_ty, llvm_i32_ty]>;

and verifier would verify it through VerifyIntrinsicType(). I think I will just modify the first assert to check the relocated value must be pointer type.

I will add two more tests. One to assert VerifyIntrinsicType() fails when gc_relocate's return type is not pointer type. Another one to assert relocated value is pointer type.

Does this sound good to you?

[pgavlin]

That sounds fine to me. Thanks for digging in a bit more!

[• chenli]

Add test cases as Pat requested.

[pgavlin]

LGTM. Thanks for doing this.

lib/IR/Verifier.cpp

Assert(GCParamArgsStart <= BaseIndex && BaseIndex < GCParamArgsEnd,
            "'gc parameters' section of the statepoint call",
            &CI);
     Assert(GCParamArgsStart <= DerivedIndex && DerivedIndex < GCParamArgsEnd,
            "gc.relocate: statepoint derived index doesn't fall within the "
            "'gc parameters' section of the statepoint call",
            &CI);
 
     // gc_relocate does not need to be the same type as the relocated pointer.
-    // It can casted to the correct type later if it's desired
+    // It can casted to the correct type later if it's desired. However, it
+    // must be a pointer type and have the same address space
+    GCRelocateOperands Operands(&CI);
+    Assert(CI.getType()->isPointerTy() && Operands.getDerivedPtr()->getType()->isPointerTy(),
+           "gc.relocate: relocating a pointer should always return a pointer", &CI);
+
+    Assert(cast<PointerType>(CI.getType())->getAddressSpace() ==
+           cast<PointerType>(Operands.getDerivedPtr()->getType())->getAddressSpace(),
+           "gc.relocate: relocating a pointer shouldn't change its address space", &CI);
+
     break;
   }
   };
 }
 
 /// \brief Carefully grab the subprogram from a local scope.
 ///
 /// This carefully grabs the subprogram from a local scope, avoiding the

test/Verifier/gc_relocate_addrspace.ll

+; RUN: not llvm-as -disable-output <%s 2>&1 | FileCheck %s
+; This is to verify that gc_relocate must return a pointer with the same 
+; address space with the relocated value.
+
+; CHECK:       gc.relocate: relocating a pointer shouldn't change its address space
+; CHECK-NEXT:  %obj.relocated = call coldcc i8* @llvm.experimental.gc.relocate.p0i8(i32 %safepoint_token, i32 7, i32 7) ;
+
+declare void @foo()
+
+; Function Attrs: nounwind
+declare i32 @llvm.experimental.gc.statepoint.p0f_isVoidf(i64, i32, void ()*, i32, i32, ...) #0
+
+define void @test1(i64 addrspace(1)* %obj) gc "statepoint-example" {
+entry:
+  %safepoint_token = call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 0, i64 addrspace(1)* %obj)
+  %obj.relocated = call coldcc i8* @llvm.experimental.gc.relocate.p0i8(i32 %safepoint_token, i32 7, i32 7) ; (%obj, %obj)
+  ret void
+}
+
+; Function Attrs: nounwind
+declare i8* @llvm.experimental.gc.relocate.p0i8(i32, i32, i32) #0
+
+attributes #0 = { nounwind }