Class Hierarchy Analysis (CHA)

The class linker now tracks whether a method has a single implementation
and if so, the JIT compiler will try to devirtualize a virtual call for
the method into a direct call. If the single-implementation assumption
is violated due to additional class linking, compiled code that makes the
assumption is invalidated. Deoptimization is triggered for compiled code
live on stack. Instead of patching return pc's on stack, a CHA guard is
added which checks a hidden should_deoptimize flag for deoptimization.
This approach limits the number of deoptimization points.

This CL does not devirtualize abstract/interface method invocation.

Slides on CHA:
https://docs.google.com/a/google.com/presentation/d/1Ax6cabP1vM44aLOaJU3B26n5fTE9w5YU-1CRevIDsBc/edit?usp=sharing

Change-Id: I18bf716a601b6413b46312e925a6ad9e4008efa4
Test: ART_TEST_JIT=true m test-art-host/target-run-test test-art-host-gtest

1 files changed, 20 insertions, 0 deletions

diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 1f5981682b..ed6eef1b55 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -1329,6 +1329,13 @@ void CodeGeneratorARM::GenerateFrameEntry() {
     __ cfi().AdjustCFAOffset(kArmWordSize * POPCOUNT(fpu_spill_mask_));
     __ cfi().RelOffsetForMany(DWARFReg(S0), 0, fpu_spill_mask_, kArmWordSize);
   }
+
+  if (GetGraph()->HasShouldDeoptimizeFlag()) {
+    // Initialize should_deoptimize flag to 0.
+    __ mov(IP, ShifterOperand(0));
+    __ StoreToOffset(kStoreWord, IP, SP, -kShouldDeoptimizeFlagSize);
+  }
+
   int adjust = GetFrameSize() - FrameEntrySpillSize();
   __ AddConstant(SP, -adjust);
   __ cfi().AdjustCFAOffset(adjust);
@@ -1944,6 +1951,19 @@ void InstructionCodeGeneratorARM::VisitDeoptimize(HDeoptimize* deoptimize) {
                         /* false_target */ nullptr);
 }
 
+void LocationsBuilderARM::VisitShouldDeoptimizeFlag(HShouldDeoptimizeFlag* flag) {
+  LocationSummary* locations = new (GetGraph()->GetArena())
+      LocationSummary(flag, LocationSummary::kNoCall);
+  locations->SetOut(Location::RequiresRegister());
+}
+
+void InstructionCodeGeneratorARM::VisitShouldDeoptimizeFlag(HShouldDeoptimizeFlag* flag) {
+  __ LoadFromOffset(kLoadWord,
+                    flag->GetLocations()->Out().AsRegister<Register>(),
+                    SP,
+                    codegen_->GetStackOffsetOfShouldDeoptimizeFlag());
+}
+
 void LocationsBuilderARM::VisitSelect(HSelect* select) {
   LocationSummary* locations = new (GetGraph()->GetArena()) LocationSummary(select);
   if (Primitive::IsFloatingPointType(select->GetType())) {