[ownership] Teach the load_borrow verifier that value_metatype of an address isn't a write.

Just a case where the verifier was too sensitive. The only places that we use
this in terms of optimization would just not optimize in this case, so no
miscompiles are possible. That being said, we should ensure that SILGen doesn't
hit a verifier error after it emits code.

rdar://78698170 [SR-14680]

Author: gottesmm

lib/SIL/Verifier/LoadBorrowImmutabilityChecker.cpp

@@ -88,7 +88,6 @@ bool GatherWritesVisitor::visitUse(Operand *op, AccessUseType useTy) {
     return true;
   }
   switch (user->getKind()) {
-
   // Known reads...
   case SILInstructionKind::LoadBorrowInst:
   case SILInstructionKind::SelectEnumAddrInst:
@@ -100,6 +99,7 @@ bool GatherWritesVisitor::visitUse(Operand *op, AccessUseType useTy) {
   case SILInstructionKind::IsUniqueInst:
   case SILInstructionKind::HopToExecutorInst:
   case SILInstructionKind::ExtractExecutorInst:
+  case SILInstructionKind::ValueMetatypeInst:
     return true;
 
   // Known writes...

test/SIL/ownership-verifier/load_borrow_invalidation_test.sil

@@ -410,3 +410,21 @@ bb0(%0 : $*Builtin.NativeObject):
   return %2 : $Bool
 }
 
+sil [ossa] @test_valuemetatype : $@convention(thin) (@owned Builtin.NativeObject) -> () {
+bb0(%0 : @owned $Builtin.NativeObject):
+  %1 = alloc_stack $Builtin.NativeObject
+  store %0 to [init] %1 : $*Builtin.NativeObject
+  %3a = value_metatype $@thick Builtin.NativeObject.Type, %1 : $*Builtin.NativeObject
+  %2 = load_borrow %1 : $*Builtin.NativeObject
+  %gUser = function_ref @guaranteedUser : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  apply %gUser(%2) : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  end_borrow %2 : $Builtin.NativeObject
+  %3 = address_to_pointer %1 : $*Builtin.NativeObject to $Builtin.RawPointer
+  %4 = mark_dependence %3 : $Builtin.RawPointer on %1 : $*Builtin.NativeObject
+  %rawPointerUser = function_ref @useRawPointer : $@convention(thin) (Builtin.RawPointer) -> ()
+  apply %rawPointerUser(%4) : $@convention(thin) (Builtin.RawPointer) -> ()
+  destroy_addr %1 : $*Builtin.NativeObject
+  dealloc_stack %1 : $*Builtin.NativeObject
+  %9999 = tuple()
+  return %9999 : $()
+}