Refactor GetIMTIndex

This allows us to more easily maintain and experiment with
interface method table indexing and hashing.

Change-Id: I719920fae7490dcedcda7c1c36db225c2b8b16df
diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index 4406c0a..4259aea 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -6167,11 +6167,6 @@
   }
 }
 
-static inline uint32_t GetIMTIndex(ArtMethod* interface_method)
-    SHARED_REQUIRES(Locks::mutator_lock_) {
-  return interface_method->GetDexMethodIndex() % ImTable::kSize;
-}
-
 ImtConflictTable* ClassLinker::CreateImtConflictTable(size_t count,
                                                       LinearAlloc* linear_alloc,
                                                       size_t image_pointer_size) {
@@ -6223,7 +6218,7 @@
       // or interface methods in the IMT here they will not create extra conflicts since we compare
       // names and signatures in SetIMTRef.
       ArtMethod* interface_method = interface->GetVirtualMethod(j, image_pointer_size_);
-      const uint32_t imt_index = GetIMTIndex(interface_method);
+      const uint32_t imt_index = interface_method->GetImtIndex();
 
       // There is only any conflicts if all of the interface methods for an IMT slot don't have
       // the same implementation method, keep track of this to avoid creating a conflict table in
@@ -6277,7 +6272,7 @@
         }
         DCHECK(implementation_method != nullptr);
         ArtMethod* interface_method = interface->GetVirtualMethod(j, image_pointer_size_);
-        const uint32_t imt_index = GetIMTIndex(interface_method);
+        const uint32_t imt_index = interface_method->GetImtIndex();
         if (!imt[imt_index]->IsRuntimeMethod() ||
             imt[imt_index] == unimplemented_method ||
             imt[imt_index] == imt_conflict_method) {
@@ -6683,7 +6678,7 @@
         auto* interface_method = iftable->GetInterface(i)->GetVirtualMethod(j, image_pointer_size_);
         MethodNameAndSignatureComparator interface_name_comparator(
             interface_method->GetInterfaceMethodIfProxy(image_pointer_size_));
-        uint32_t imt_index = GetIMTIndex(interface_method);
+        uint32_t imt_index = interface_method->GetImtIndex();
         ArtMethod** imt_ptr = &out_imt[imt_index];
         // For each method listed in the interface's method list, find the
         // matching method in our class's method list.  We want to favor the