Refactor GetIMTIndex

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

Change-Id: I719920fae7490dcedcda7c1c36db225c2b8b16df
diff --git a/compiler/optimizing/code_generator_mips64.cc b/compiler/optimizing/code_generator_mips64.cc
index 8d5dc84..539abf1 100644
--- a/compiler/optimizing/code_generator_mips64.cc
+++ b/compiler/optimizing/code_generator_mips64.cc
@@ -2954,7 +2954,7 @@
   __ LoadFromOffset(kLoadDoubleword, temp, temp,
       mirror::Class::ImtPtrOffset(kMips64PointerSize).Uint32Value());
   uint32_t method_offset = static_cast<uint32_t>(ImTable::OffsetOfElement(
-      invoke->GetImtIndex() % ImTable::kSize, kMips64PointerSize));
+      invoke->GetImtIndex(), kMips64PointerSize));
   // temp = temp->GetImtEntryAt(method_offset);
   __ LoadFromOffset(kLoadDoubleword, temp, temp, method_offset);
   // T9 = temp->GetEntryPoint();