Better handling of Phi nodes with constant inputs

src/hydrogen.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3509 matching lines @@
         HValue* use = it.value();
         if (use->IsPhi()) {
           int id = HPhi::cast(use)->phi_id();
           if (connected_phis[i]->UnionIsChanged(*connected_phis[id]))
             change = true;
         }
       }
     }
   }
 
-  // (3a) Use the phi reachability information from step 2 to
+  // Simplify constant phi inputs where possible.
+  for (int i = 0; i < phi_count; ++i) {
+    phi_list->at(i)->SimplifyConstantInputs();
+  }
+
+  // Use the phi reachability information from step 2 to
   // push information about values which can't be converted to integer
   // without deoptimization through the phi use-def chains, avoiding
   // unnecessary deoptimizations later.
   for (int i = 0; i < phi_count; ++i) {
     HPhi* phi = phi_list->at(i);
     bool cti = phi->AllOperandsConvertibleToInteger();
     if (cti) continue;
 
     for (BitVector::Iterator it(connected_phis.at(i));
          !it.Done();
          it.Advance()) {
       HPhi* phi = phi_list->at(it.Current());
       phi->set_is_convertible_to_integer(false);
     }
   }
 
-  // (3b) Use the phi reachability information from step 2 to
+  // Use the phi reachability information from step 2 to
   // sum up the non-phi use counts of all connected phis.
   for (int i = 0; i < phi_count; ++i) {
     HPhi* phi = phi_list->at(i);
     for (BitVector::Iterator it(connected_phis.at(i));
          !it.Done();
          it.Advance()) {
       int index = it.Current();
       HPhi* it_use = phi_list->at(index);
       if (index != i) phi->AddNonPhiUsesFrom(it_use);  // Don't count twice.
     }
@@ skipping 5889 matching lines @@
   HValue* context = environment()->LookupContext();
   HInstruction* instr =
       HMul::New(zone(), context, value, graph()->GetConstantMinus1());
   TypeInfo info = oracle()->UnaryType(expr);
   Representation rep = ToRepresentation(info);
   if (info.IsUninitialized()) {
     AddSoftDeoptimize();
     info = TypeInfo::Unknown();
   }
   if (instr->IsBinaryOperation()) {
-    HBinaryOperation::cast(instr)->set_observed_input_representation(rep, rep);
+    HBinaryOperation::cast(instr)->set_observed_input_representation(1, rep);
+    HBinaryOperation::cast(instr)->set_observed_input_representation(2, rep);
   }
   return ast_context()->ReturnInstruction(instr, expr->id());
 }
 
 
 void HOptimizedGraphBuilder::VisitBitNot(UnaryOperation* expr) {
   CHECK_ALIVE(VisitForValue(expr->expression()));
   HValue* value = Pop();
   TypeInfo info = oracle()->UnaryType(expr);
   if (info.IsUninitialized()) {
@@ skipping 420 matching lines @@
       break;
     case Token::SHL:
       instr = HShl::New(zone(), context, left, right);
       break;
     default:
       UNREACHABLE();
   }
 
   if (instr->IsBinaryOperation()) {
     HBinaryOperation* binop = HBinaryOperation::cast(instr);
-    binop->set_observed_input_representation(left_rep, right_rep);
+    binop->set_observed_input_representation(1, left_rep);
+    binop->set_observed_input_representation(2, right_rep);
     binop->initialize_output_representation(result_rep);
   }
   return instr;
 }
 
 
 // Check for the form (%_ClassOf(foo) === 'BarClass').
 static bool IsClassOfTest(CompareOperation* expr) {
   if (expr->op() != Token::EQ_STRICT) return false;
   CallRuntime* call = expr->left()->AsCallRuntime();
@@ skipping 359 matching lines @@
     AddInstruction(new(zone()) HCheckNonSmi(right));
     AddInstruction(HCheckInstanceType::NewIsInternalizedString(right, zone()));
     HCompareObjectEqAndBranch* result =
         new(zone()) HCompareObjectEqAndBranch(left, right);
     result->set_position(expr->position());
     return ast_context()->ReturnControl(result, expr->id());
   } else {
     if (combined_rep.IsTagged() || combined_rep.IsNone()) {
       HCompareGeneric* result =
           new(zone()) HCompareGeneric(context, left, right, op);
-      result->set_observed_input_representation(left_rep, right_rep);
+      result->set_observed_input_representation(1, left_rep);
+      result->set_observed_input_representation(2, right_rep);
       result->set_position(expr->position());
       return ast_context()->ReturnInstruction(result, expr->id());
     } else {
       HCompareIDAndBranch* result =
           new(zone()) HCompareIDAndBranch(left, right, op);
       result->set_observed_input_representation(left_rep, right_rep);
       result->set_position(expr->position());
       return ast_context()->ReturnControl(result, expr->id());
     }
   }
@@ skipping 1630 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal