Better handling of Phi nodes with constant inputs

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 9ca78ccc84454c2f20140f22614b5951b79911e9..15861a81f85922e3eddddb04eebc6a285b4b14aa 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -3527,7 +3527,12 @@ void HInferRepresentation::Analyze() {
     }
   }
 
-  // (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.
@@ -3544,7 +3549,7 @@ void HInferRepresentation::Analyze() {
     }
   }
 
-  // (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);
@@ -9454,7 +9459,8 @@ void HOptimizedGraphBuilder::VisitSub(UnaryOperation* expr) {
     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());
 }
@@ -9895,7 +9901,8 @@ HInstruction* HOptimizedGraphBuilder::BuildBinaryOperation(
 
   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;
@@ -10275,7 +10282,8 @@ void HOptimizedGraphBuilder::VisitCompareOperation(CompareOperation* expr) {
     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 {