Hydrogen: Re-use regular comparisons infrastructure for switch statements

src/hydrogen.cc

 // Copyright 2013 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 4118 matching lines @@
   ASSERT(current_block()->HasPredecessor());
   return Bailout(kWithStatement);
 }
 
 
 void HOptimizedGraphBuilder::VisitSwitchStatement(SwitchStatement* stmt) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
 
-  // We only optimize switch statements with smi-literal smi comparisons,
-  // with a bounded number of clauses.
+  // We only optimize switch statements with a bounded number of clauses.
   const int kCaseClauseLimit = 128;
   ZoneList<CaseClause*>* clauses = stmt->cases();
   int clause_count = clauses->length();
   ZoneList<HBasicBlock*> body_blocks(clause_count, zone());
   if (clause_count > kCaseClauseLimit) {
     return Bailout(kSwitchStatementTooManyClauses);
   }
 
-  ASSERT(stmt->switch_type() != SwitchStatement::UNKNOWN_SWITCH);
-
   CHECK_ALIVE(VisitForValue(stmt->tag()));
   Add<HSimulate>(stmt->EntryId());
   HValue* tag_value = Top();
-
-  HUnaryControlInstruction* string_check = NULL;
-  HBasicBlock* not_string_block = NULL;
-
-  // Test switch's tag value if all clauses are string literals
-  if (stmt->switch_type() == SwitchStatement::STRING_SWITCH) {
-    HBasicBlock* first_test_block = graph()->CreateBasicBlock();
-    not_string_block = graph()->CreateBasicBlock();
-    string_check = New<HIsStringAndBranch>(
-        tag_value, first_test_block, not_string_block);
-    FinishCurrentBlock(string_check);
-
-    set_current_block(not_string_block);
-    Drop(1);  // tag_value
-
-    set_current_block(first_test_block);
-  }
+  Handle<Type> tag_type = stmt->tag()->bounds().lower;
 
   // 1. Build all the tests, with dangling true branches
   BailoutId default_id = BailoutId::None();
   for (int i = 0; i < clause_count; ++i) {
     CaseClause* clause = clauses->at(i);
     if (clause->is_default()) {
       body_blocks.Add(NULL, zone());
       if (default_id.IsNone()) default_id = clause->EntryId();
       continue;
     }
 
     // Generate a compare and branch.
     CHECK_ALIVE(VisitForValue(clause->label()));
     HValue* label_value = Pop();
 
-    HControlInstruction* compare;
-
-    if (stmt->switch_type() == SwitchStatement::SMI_SWITCH) {
-      if (!clause->compare_type()->Is(Type::Smi())) {
-        Add<HDeoptimize>("Non-smi switch type", Deoptimizer::SOFT);
-      }
-
-      HCompareNumericAndBranch* compare_ =
-          New<HCompareNumericAndBranch>(tag_value,
-                                        label_value,
-                                        Token::EQ_STRICT);
-      compare_->set_observed_input_representation(
-          Representation::Smi(), Representation::Smi());
-      compare = compare_;
-    } else if (stmt->switch_type() == SwitchStatement::STRING_SWITCH) {
-      compare = New<HStringCompareAndBranch>(tag_value,
-                                             label_value,
-                                             Token::EQ_STRICT);
-    } else {
-      HValue* test = Add<HCompareGeneric>(tag_value,
-                                          label_value,
-                                          Token::EQ_STRICT);
-      if (test->HasObservableSideEffects()) {
-        Push(test);
-        Add<HSimulate>(clause->id(), REMOVABLE_SIMULATE);
-        Drop(1);
-      }
-      compare = New<HBranch>(test);
-    }
+    Handle<Type> label_type = clause->label()->bounds().lower;
+    Handle<Type> combined_type = clause->compare_type();
+    HControlInstruction* compare = BuildCompareInstruction(
+        Token::EQ_STRICT, tag_value, label_value, tag_type, label_type,
+        combined_type, stmt->tag()->position(), clause->label()->position(),
+        clause->id());
 
     HBasicBlock* next_test_block = graph()->CreateBasicBlock();
     HBasicBlock* body_block = graph()->CreateBasicBlock();
     body_blocks.Add(body_block, zone());
     compare->SetSuccessorAt(0, body_block);
     compare->SetSuccessorAt(1, next_test_block);
     FinishCurrentBlock(compare);
 
     set_current_block(body_block);
     Drop(1);  // tag_value
 
     set_current_block(next_test_block);
   }
 
   // Save the current block to use for the default or to join with the
   // exit.
   HBasicBlock* last_block = current_block();
   Drop(1);  // tag_value
 
-  if (not_string_block != NULL) {
-    BailoutId join_id = !default_id.IsNone() ? default_id : stmt->ExitId();
-    last_block = CreateJoin(last_block, not_string_block, join_id);
-  }
-
   // 2. Loop over the clauses and the linked list of tests in lockstep,
   // translating the clause bodies.
   HBasicBlock* fall_through_block = NULL;
 
   BreakAndContinueInfo break_info(stmt);
   { BreakAndContinueScope push(&break_info, this);
     for (int i = 0; i < clause_count; ++i) {
       CaseClause* clause = clauses->at(i);
 
       // Identify the block where normal (non-fall-through) control flow
@@ skipping 4886 matching lines @@
     HValue* value = Pop();
     Literal* literal = expr->right()->AsLiteral();
     Handle<String> rhs = Handle<String>::cast(literal->value());
     HClassOfTestAndBranch* instr = New<HClassOfTestAndBranch>(value, rhs);
     return ast_context()->ReturnControl(instr, expr->id());
   }
 
   Handle<Type> left_type = expr->left()->bounds().lower;
   Handle<Type> right_type = expr->right()->bounds().lower;
   Handle<Type> combined_type = expr->combined_type();
-  Representation combined_rep = Representation::FromType(combined_type);

[rossberg, 2013/12/11 09:41:34]

Not sure this matters, but deferring the conversion to later changes the
behaviour in the cases where the types get changed below (e.g. when
combined_type is None).

[Jakob Kummerow, 2013/12/11 10:00:01]

Nope, doesn't matter. 
The only change we'd do to the types is None -> Any, these get mapped to
representations None and Tagged, respectively, which are handled in the same
way. This is not just a brittle coincidence; it's the way the system works.

[rossberg, 2013/12/11 11:35:27]

Yes, I assumed as much. Though I still wonder why we have to change the types to
Any at all then.

-  Representation left_rep = Representation::FromType(left_type);
-  Representation right_rep = Representation::FromType(right_type);
 
   CHECK_ALIVE(VisitForValue(expr->left()));
   CHECK_ALIVE(VisitForValue(expr->right()));
 
   if (FLAG_emit_opt_code_positions) SetSourcePosition(expr->position());
 
   HValue* right = Pop();
   HValue* left = Pop();
   Token::Value op = expr->op();
 
@@ skipping 53 matching lines @@
 
   // Cases handled below depend on collected type feedback. They should
   // soft deoptimize when there is no type feedback.
   if (combined_type->Is(Type::None())) {
     Add<HDeoptimize>("Insufficient type feedback for combined type "
                      "of binary operation",
                      Deoptimizer::SOFT);
     combined_type = left_type = right_type = handle(Type::Any(), isolate());
   }
 
+  HControlInstruction* compare = BuildCompareInstruction(
+      op, left, right, left_type, right_type, combined_type,
+      expr->left()->position(), expr->right()->position(), expr->id());
+  if (compare == NULL) return;  // Bailed out.
+  return ast_context()->ReturnControl(compare, expr->id());
+}
+
+
+HControlInstruction* HOptimizedGraphBuilder::BuildCompareInstruction(
+    Token::Value op,
+    HValue* left,
+    HValue* right,
+    Handle<Type> left_type,
+    Handle<Type> right_type,
+    Handle<Type> combined_type,
+    int left_position,
+    int right_position,
+    BailoutId bailout_id) {
+  Representation left_rep = Representation::FromType(left_type);
+  Representation right_rep = Representation::FromType(right_type);
+  Representation combined_rep = Representation::FromType(combined_type);
+
   if (combined_type->Is(Type::Receiver())) {
-    switch (op) {
-      case Token::EQ:
-      case Token::EQ_STRICT: {
-        // Can we get away with map check and not instance type check?
-        if (combined_type->IsClass()) {
-          Handle<Map> map = combined_type->AsClass();
-          AddCheckMap(left, map);
-          AddCheckMap(right, map);
-          HCompareObjectEqAndBranch* result =
-              New<HCompareObjectEqAndBranch>(left, right);
-          if (FLAG_emit_opt_code_positions) {
-            result->set_operand_position(zone(), 0, expr->left()->position());
-            result->set_operand_position(zone(), 1, expr->right()->position());
-          }
-          return ast_context()->ReturnControl(result, expr->id());
-        } else {
-          BuildCheckHeapObject(left);
-          Add<HCheckInstanceType>(left, HCheckInstanceType::IS_SPEC_OBJECT);
-          BuildCheckHeapObject(right);
-          Add<HCheckInstanceType>(right, HCheckInstanceType::IS_SPEC_OBJECT);
-          HCompareObjectEqAndBranch* result =
-              New<HCompareObjectEqAndBranch>(left, right);
-          return ast_context()->ReturnControl(result, expr->id());
+    if (Token::IsEqualityOp(op)) {
+      // Can we get away with map check and not instance type check?
+      if (combined_type->IsClass()) {
+        Handle<Map> map = combined_type->AsClass();
+        AddCheckMap(left, map);
+        AddCheckMap(right, map);
+        HCompareObjectEqAndBranch* result =
+            New<HCompareObjectEqAndBranch>(left, right);
+        if (FLAG_emit_opt_code_positions) {
+          result->set_operand_position(zone(), 0, left_position);
+          result->set_operand_position(zone(), 1, right_position);
         }
+        return result;
+      } else {
+        BuildCheckHeapObject(left);
+        Add<HCheckInstanceType>(left, HCheckInstanceType::IS_SPEC_OBJECT);
+        BuildCheckHeapObject(right);
+        Add<HCheckInstanceType>(right, HCheckInstanceType::IS_SPEC_OBJECT);
+        HCompareObjectEqAndBranch* result =
+            New<HCompareObjectEqAndBranch>(left, right);
+        return result;
       }
-      default:
-        return Bailout(kUnsupportedNonPrimitiveCompare);
+    } else {
+      Bailout(kUnsupportedNonPrimitiveCompare);
+      return NULL;
     }
   } else if (combined_type->Is(Type::InternalizedString()) &&
              Token::IsEqualityOp(op)) {
     BuildCheckHeapObject(left);
     Add<HCheckInstanceType>(left, HCheckInstanceType::IS_INTERNALIZED_STRING);
     BuildCheckHeapObject(right);
     Add<HCheckInstanceType>(right, HCheckInstanceType::IS_INTERNALIZED_STRING);
     HCompareObjectEqAndBranch* result =
         New<HCompareObjectEqAndBranch>(left, right);
-    return ast_context()->ReturnControl(result, expr->id());
+    return result;
   } else if (combined_type->Is(Type::String())) {
     BuildCheckHeapObject(left);
     Add<HCheckInstanceType>(left, HCheckInstanceType::IS_STRING);
     BuildCheckHeapObject(right);
     Add<HCheckInstanceType>(right, HCheckInstanceType::IS_STRING);
     HStringCompareAndBranch* result =
         New<HStringCompareAndBranch>(left, right, op);
-    return ast_context()->ReturnControl(result, expr->id());
+    return result;
   } else {
     if (combined_rep.IsTagged() || combined_rep.IsNone()) {
-      HCompareGeneric* result = New<HCompareGeneric>(left, right, op);
+      HCompareGeneric* result = Add<HCompareGeneric>(left, right, op);
       result->set_observed_input_representation(1, left_rep);
       result->set_observed_input_representation(2, right_rep);
-      return ast_context()->ReturnInstruction(result, expr->id());
+      if (result->HasObservableSideEffects()) {
+        Push(result);
+        AddSimulate(bailout_id, REMOVABLE_SIMULATE);
+        Drop(1);
+      }
+      // TODO(jkummerow): Can we make this more efficient?
+      HBranch* branch = New<HBranch>(result);
+      return branch;
     } else {
       HCompareNumericAndBranch* result =
           New<HCompareNumericAndBranch>(left, right, op);
       result->set_observed_input_representation(left_rep, right_rep);
       if (FLAG_emit_opt_code_positions) {
-        result->SetOperandPositions(zone(),
-                                    expr->left()->position(),
-                                    expr->right()->position());
+        result->SetOperandPositions(zone(), left_position, right_position);
       }
-      return ast_context()->ReturnControl(result, expr->id());
+      return result;
     }
   }
 }
 
 
 void HOptimizedGraphBuilder::HandleLiteralCompareNil(CompareOperation* expr,
                                                      Expression* sub_expr,
                                                      NilValue nil) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
@@ skipping 1510 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal