commit badee9820fcf5dca5f8c46c3215ae1779ee7736e
author Nelli Kim <nelli.kim@samsung.com> Fri May 13 13:08:53 2016 +0300
committer Matthew Gharrity <gharrma@google.com> Tue Jun 14 10:05:47 2016 -0700
tree 982948a67a88a1f9a734c935f919f8d307969f48
parent 614968198625a6693666bdc1e5609e2f663f5638

Optimize IMT

* Remove IMT for classes which do not implement interfaces
* Remove IMT for array classes
* Share same IMT

Saved memory (measured on hammerhead):
boot.art:
Total number of classes: 3854
Number of affected classes: 1637
Saved memory: 409kB

Chrome (excluding classes in boot.art):
Total number of classes: 2409
Number of affected classes: 1259
Saved memory: 314kB

Google Maps (excluding classes in boot.art):
Total number of classes: 6988
Number of affected classes: 2574
Saved memory: 643kB

Performance regression on benchmarks/InvokeInterface.java benchmark
(measured timeCall10Interface)
1st launch: 9.6%
2nd launch: 6.8%

Change-Id: If07e45390014a6ee8f3c1c4ca095b43046f0871f

compiler/optimizing/code_generator_arm64.cc

diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index a37ea1e..b63a3d4 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -3490,8 +3490,6 @@
   // TODO: b/18116999, our IMTs can miss an IncompatibleClassChangeError.
   LocationSummary* locations = invoke->GetLocations();
   Register temp = XRegisterFrom(locations->GetTemp(0));
-  uint32_t method_offset = mirror::Class::EmbeddedImTableEntryOffset(
-      invoke->GetImtIndex() % mirror::Class::kImtSize, kArm64PointerSize).Uint32Value();
   Location receiver = locations->InAt(0);
   Offset class_offset = mirror::Object::ClassOffset();
   Offset entry_point = ArtMethod::EntryPointFromQuickCompiledCodeOffset(kArm64WordSize);
@@ -3521,6 +3519,10 @@
   // intact/accessible until the end of the marking phase (the
   // concurrent copying collector may not in the future).
   GetAssembler()->MaybeUnpoisonHeapReference(temp.W());
+  __ Ldr(temp,
+      MemOperand(temp, mirror::Class::ImtPtrOffset(kArm64PointerSize).Uint32Value()));
+  uint32_t method_offset = static_cast<uint32_t>(ImTable::OffsetOfElement(
+      invoke->GetImtIndex() % ImTable::kSize, kArm64PointerSize));
   // temp = temp->GetImtEntryAt(method_offset);
   __ Ldr(temp, MemOperand(temp, method_offset));
   // lr = temp->GetEntryPoint();
@@ -5148,8 +5150,10 @@
     method_offset = mirror::Class::EmbeddedVTableEntryOffset(
         instruction->GetIndex(), kArm64PointerSize).SizeValue();
   } else {
-    method_offset = mirror::Class::EmbeddedImTableEntryOffset(
-        instruction->GetIndex() % mirror::Class::kImtSize, kArm64PointerSize).Uint32Value();
+    __ Ldr(XRegisterFrom(locations->Out()), MemOperand(XRegisterFrom(locations->InAt(0)),
+        mirror::Class::ImtPtrOffset(kArm64PointerSize).Uint32Value()));
+    method_offset = static_cast<uint32_t>(ImTable::OffsetOfElement(
+        instruction->GetIndex() % ImTable::kSize, kArm64PointerSize));
   }
   __ Ldr(XRegisterFrom(locations->Out()),
          MemOperand(XRegisterFrom(locations->InAt(0)), method_offset));