Disabled PC-relative calls for object allocations

[mkustermann]

The change in 91ed534 has disabled PC-relative calls for allocation stubs. The corresponding code was commented out:

diff --git a/runtime/vm/compiler/stub_code_compiler_arm64.cc b/runtime/vm/compiler/stub_code_compiler_arm64.cc
index db103f75f2f..afc9b109efa 100644
--- a/runtime/vm/compiler/stub_code_compiler_arm64.cc
+++ b/runtime/vm/compiler/stub_code_compiler_arm64.cc
@@ -2266,7 +2266,9 @@ void StubCodeCompiler::GenerateAllocationStubForClass(
       !target::Class::TraceAllocation(cls) &&
       target::SizeFitsInSizeTag(instance_size)) {
     if (is_cls_parameterized) {
-      if (!IsSameObject(NullObject(),
+      // TODO(41974): Assign all allocation stubs to the root loading unit?
+      if (false &&
+          !IsSameObject(NullObject(),
                         CastHandle<Object>(allocat_object_parametrized))) {
         __ GenerateUnRelocatedPcRelativeTailCall();
         unresolved_calls->Add(new UnresolvedPcRelativeCall(
@@ -2279,7 +2281,9 @@ void StubCodeCompiler::GenerateAllocationStubForClass(
         __ br(R4);
       }
     } else {
-      if (!IsSameObject(NullObject(), CastHandle<Object>(allocate_object))) {
+      // TODO(41974): Assign all allocation stubs to the root loading unit?
+      if (false &&
+          !IsSameObject(NullObject(), CastHandle<Object>(allocate_object))) {
         __ GenerateUnRelocatedPcRelativeTailCall();
         unresolved_calls->Add(new UnresolvedPcRelativeCall(
             __ CodeSize(), allocate_object, /*is_tail_call=*/true));

The referenced #41974 is already closed.

/cc @rmacnak-google

[mraleph]

At the very least we should replace false with a check that there is a single unit.

[aam]

https://dart.googlesource.com/sdk/+/4c498a48c38d44d71c8586e5d4421cfe34244340 with the fix.