Revert "Revert "Optimize IMT""

This reverts commit 88f288e3564d79d87c0cd8bb831ec5a791ba4861.

Change-Id: I49605d53692cbec1e2622e23ff2893fc51ed4115
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 5e30203..cac33cd 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -2257,8 +2257,6 @@
   LocationSummary* locations = invoke->GetLocations();
   CpuRegister temp = locations->GetTemp(0).AsRegister<CpuRegister>();
   CpuRegister hidden_reg = locations->GetTemp(1).AsRegister<CpuRegister>();
-  uint32_t method_offset = mirror::Class::EmbeddedImTableEntryOffset(
-      invoke->GetImtIndex() % mirror::Class::kImtSize, kX86_64PointerSize).Uint32Value();
   Location receiver = locations->InAt(0);
   size_t class_offset = mirror::Object::ClassOffset().SizeValue();
 
@@ -2284,6 +2282,12 @@
   // intact/accessible until the end of the marking phase (the
   // concurrent copying collector may not in the future).
   __ MaybeUnpoisonHeapReference(temp);
+  // temp = temp->GetAddressOfIMT()
+  __ movq(temp,
+      Address(temp, mirror::Class::ImtPtrOffset(kX86_64PointerSize).Uint32Value()));
+  // temp = temp->GetImtEntryAt(method_offset);
+  uint32_t method_offset = static_cast<uint32_t>(ImTable::OffsetOfElement(
+      invoke->GetImtIndex() % ImTable::kSize, kX86_64PointerSize));
   // temp = temp->GetImtEntryAt(method_offset);
   __ movq(temp, Address(temp, method_offset));
   // call temp->GetEntryPoint();
@@ -4007,8 +4011,11 @@
     method_offset = mirror::Class::EmbeddedVTableEntryOffset(
         instruction->GetIndex(), kX86_64PointerSize).SizeValue();
   } else {
-    method_offset = mirror::Class::EmbeddedImTableEntryOffset(
-        instruction->GetIndex() % mirror::Class::kImtSize, kX86_64PointerSize).Uint32Value();
+    __ movq(locations->Out().AsRegister<CpuRegister>(),
+            Address(locations->InAt(0).AsRegister<CpuRegister>(),
+            mirror::Class::ImtPtrOffset(kX86_64PointerSize).Uint32Value()));
+    method_offset = static_cast<uint32_t>(ImTable::OffsetOfElement(
+        instruction->GetIndex() % ImTable::kSize, kX86_64PointerSize));
   }
   __ movq(locations->Out().AsRegister<CpuRegister>(),
           Address(locations->InAt(0).AsRegister<CpuRegister>(), method_offset));