Generalize codegen and simplification of deopt.

Rationale: the de-opt instruction is very similar to an if,
           so the existing assumption that it always has a
           conditional "under the hood" is very unsafe, since
           optimizations may have replaced conditionals with
           actual values; this CL generalizes handling of deopt.

Change-Id: I1c6cb71fdad2af869fa4714b38417dceed676459

6 files changed, 18 insertions, 10 deletions

diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 1df6818549..358a35c483 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -1377,8 +1377,7 @@ void LocationsBuilderARM::VisitDeoptimize(HDeoptimize* deoptimize) {
   LocationSummary* locations = new (GetGraph()->GetArena())
       LocationSummary(deoptimize, LocationSummary::kCallOnSlowPath);
   HInstruction* cond = deoptimize->InputAt(0);
-  DCHECK(cond->IsCondition());
-  if (cond->AsCondition()->NeedsMaterialization()) {
+  if (!cond->IsCondition() || cond->AsCondition()->NeedsMaterialization()) {
     locations->SetInAt(0, Location::RequiresRegister());
   }
 }
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index 4e33ee15da..37f10a5cc5 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -2356,8 +2356,7 @@ void LocationsBuilderARM64::VisitDeoptimize(HDeoptimize* deoptimize) {
   LocationSummary* locations = new (GetGraph()->GetArena())
       LocationSummary(deoptimize, LocationSummary::kCallOnSlowPath);
   HInstruction* cond = deoptimize->InputAt(0);
-  DCHECK(cond->IsCondition());
-  if (cond->AsCondition()->NeedsMaterialization()) {
+  if (!cond->IsCondition() || cond->AsCondition()->NeedsMaterialization()) {
     locations->SetInAt(0, Location::RequiresRegister());
   }
 }
diff --git a/compiler/optimizing/code_generator_mips64.cc b/compiler/optimizing/code_generator_mips64.cc
index eb20291e20..f561c97eb0 100644
--- a/compiler/optimizing/code_generator_mips64.cc
+++ b/compiler/optimizing/code_generator_mips64.cc
@@ -2223,8 +2223,7 @@ void LocationsBuilderMIPS64::VisitDeoptimize(HDeoptimize* deoptimize) {
   LocationSummary* locations = new (GetGraph()->GetArena())
       LocationSummary(deoptimize, LocationSummary::kCallOnSlowPath);
   HInstruction* cond = deoptimize->InputAt(0);
-  DCHECK(cond->IsCondition());
-  if (cond->AsCondition()->NeedsMaterialization()) {
+  if (!cond->IsCondition() || cond->AsCondition()->NeedsMaterialization()) {
     locations->SetInAt(0, Location::RequiresRegister());
   }
 }
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 9de159251f..8b33f56295 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -1307,8 +1307,7 @@ void LocationsBuilderX86::VisitDeoptimize(HDeoptimize* deoptimize) {
   LocationSummary* locations = new (GetGraph()->GetArena())
       LocationSummary(deoptimize, LocationSummary::kCallOnSlowPath);
   HInstruction* cond = deoptimize->InputAt(0);
-  DCHECK(cond->IsCondition());
-  if (cond->AsCondition()->NeedsMaterialization()) {
+  if (!cond->IsCondition() || cond->AsCondition()->NeedsMaterialization()) {
     locations->SetInAt(0, Location::Any());
   }
 }
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index bedaa5577b..a2af4ba1f9 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -1253,8 +1253,7 @@ void LocationsBuilderX86_64::VisitDeoptimize(HDeoptimize* deoptimize) {
   LocationSummary* locations = new (GetGraph()->GetArena())
       LocationSummary(deoptimize, LocationSummary::kCallOnSlowPath);
   HInstruction* cond = deoptimize->InputAt(0);
-  DCHECK(cond->IsCondition());
-  if (cond->AsCondition()->NeedsMaterialization()) {
+  if (!cond->IsCondition() || cond->AsCondition()->NeedsMaterialization()) {
     locations->SetInAt(0, Location::Any());
   }
 }
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index d468540091..7814eb9c11 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -73,6 +73,7 @@ class InstructionSimplifierVisitor : public HGraphDelegateVisitor {
   void VisitInstanceOf(HInstanceOf* instruction) OVERRIDE;
   void VisitFakeString(HFakeString* fake_string) OVERRIDE;
   void VisitInvoke(HInvoke* invoke) OVERRIDE;
+  void VisitDeoptimize(HDeoptimize* deoptimize) OVERRIDE;
 
   bool CanEnsureNotNullAt(HInstruction* instr, HInstruction* at) const;
 
@@ -1151,4 +1152,16 @@ void InstructionSimplifierVisitor::VisitInvoke(HInvoke* instruction) {
   }
 }
 
+void InstructionSimplifierVisitor::VisitDeoptimize(HDeoptimize* deoptimize) {
+  HInstruction* cond = deoptimize->InputAt(0);
+  if (cond->IsConstant()) {
+    if (cond->AsIntConstant()->IsZero()) {
+      // Never deopt: instruction can be removed.
+      deoptimize->GetBlock()->RemoveInstruction(deoptimize);
+    } else {
+      // Always deopt.
+    }
+  }
+}
+
 }  // namespace art