Implement simple effect typing for variables

src/typing.cc

Index: src/typing.cc
diff --git a/src/typing.cc b/src/typing.cc
index 4220d2110db1118138f309f963dc19f99a059582..dd4abcfd7d1718a0224086e35a649f91ad464e9a 100644
--- a/src/typing.cc
+++ b/src/typing.cc
@@ -40,7 +40,8 @@ AstTyper::AstTyper(CompilationInfo* info)
           Handle<Code>(info->closure()->shared()->code()),
           Handle<Context>(info->closure()->context()->native_context()),
           info->isolate(),
-          info->zone()) {
+          info->zone()),
+      store_(info->zone()) {
   InitializeAstVisitor();
 }
 
@@ -85,6 +86,9 @@ void AstTyper::VisitStatements(ZoneList<Statement*>* stmts) {
 
 void AstTyper::VisitBlock(Block* stmt) {
   RECURSE(VisitStatements(stmt->statements()));
+  if (stmt->labels() != NULL) {
+    store_.Forget();  // Control may transfer here via 'break l'.
+  }
 }
 
 
@@ -98,30 +102,41 @@ void AstTyper::VisitEmptyStatement(EmptyStatement* stmt) {
 
 
 void AstTyper::VisitIfStatement(IfStatement* stmt) {
-  RECURSE(Visit(stmt->condition()));
-  RECURSE(Visit(stmt->then_statement()));
-  RECURSE(Visit(stmt->else_statement()));
-
+  // Collect type feedback.
   if (!stmt->condition()->ToBooleanIsTrue() &&
       !stmt->condition()->ToBooleanIsFalse()) {
     stmt->condition()->RecordToBooleanTypeFeedback(oracle());
   }
+
+  RECURSE(Visit(stmt->condition()));
+  Effects then_effects = EnterEffects();
+  RECURSE(Visit(stmt->then_statement()));
+  ExitEffects();
+  Effects else_effects = EnterEffects();
+  RECURSE(Visit(stmt->else_statement()));
+  ExitEffects();
+  then_effects.Alt(else_effects);
+  store_.Seq(then_effects);
 }
 
 
 void AstTyper::VisitContinueStatement(ContinueStatement* stmt) {
+  // TODO(rossberg): is it worth having a non-termination effect?
 }
 
 
 void AstTyper::VisitBreakStatement(BreakStatement* stmt) {
+  // TODO(rossberg): is it worth having a non-termination effect?
 }
 
 
 void AstTyper::VisitReturnStatement(ReturnStatement* stmt) {
-  RECURSE(Visit(stmt->expression()));
-
+  // Collect type feedback.
   // TODO(rossberg): we only need this for inlining into test contexts...
   stmt->expression()->RecordToBooleanTypeFeedback(oracle());
+
+  RECURSE(Visit(stmt->expression()));
+  // TODO(rossberg): is it worth having a non-termination effect?
 }
 
 
@@ -133,14 +148,13 @@ void AstTyper::VisitWithStatement(WithStatement* stmt) {
 
 void AstTyper::VisitSwitchStatement(SwitchStatement* stmt) {
   RECURSE(Visit(stmt->tag()));
+
   ZoneList<CaseClause*>* clauses = stmt->cases();
   SwitchStatement::SwitchType switch_type = stmt->switch_type();
   for (int i = 0; i < clauses->length(); ++i) {
     CaseClause* clause = clauses->at(i);
     if (!clause->is_default()) {
       Expression* label = clause->label();
-      RECURSE(Visit(label));
-
       SwitchStatement::SwitchType label_switch_type =
           label->IsSmiLiteral() ? SwitchStatement::SMI_SWITCH :
           label->IsStringLiteral() ? SwitchStatement::STRING_SWITCH :
@@ -149,13 +163,20 @@ void AstTyper::VisitSwitchStatement(SwitchStatement* stmt) {
         switch_type = label_switch_type;
       else if (switch_type != label_switch_type)
         switch_type = SwitchStatement::GENERIC_SWITCH;
+
+      RECURSE(Visit(label));
     }
     RECURSE(VisitStatements(clause->statements()));
   }
+
+  // TODO(rossberg): handle switch effects
+  store_.Forget();
+
   if (switch_type == SwitchStatement::UNKNOWN_SWITCH)
     switch_type = SwitchStatement::GENERIC_SWITCH;
   stmt->set_switch_type(switch_type);
 
+  // Collect type feedback.
   // TODO(rossberg): can we eliminate this special case and extra loop?
   if (switch_type == SwitchStatement::SMI_SWITCH) {
     for (int i = 0; i < clauses->length(); ++i) {
@@ -168,22 +189,30 @@ void AstTyper::VisitSwitchStatement(SwitchStatement* stmt) {
 
 
 void AstTyper::VisitDoWhileStatement(DoWhileStatement* stmt) {
-  RECURSE(Visit(stmt->body()));
-  RECURSE(Visit(stmt->cond()));
-
+  // Collect type feedback.
   if (!stmt->cond()->ToBooleanIsTrue()) {
     stmt->cond()->RecordToBooleanTypeFeedback(oracle());
   }
+
+  // TODO(rossberg): we could refine the unconditional Forget if we computed the
+  // set of variables assigned to in the loop. Same for other control transfers.
+  store_.Forget();  // Control may transfer here via looping or 'continue'.
+  RECURSE(Visit(stmt->body()));
+  RECURSE(Visit(stmt->cond()));
+  store_.Forget();  // Control may transfer here via 'break'.
 }
 
 
 void AstTyper::VisitWhileStatement(WhileStatement* stmt) {
-  RECURSE(Visit(stmt->cond()));
-  RECURSE(Visit(stmt->body()));
-
+  // Collect type feedback.
   if (!stmt->cond()->ToBooleanIsTrue()) {
     stmt->cond()->RecordToBooleanTypeFeedback(oracle());
   }
+
+  store_.Forget();  // Control may transfer here via looping or 'continue'.
+  RECURSE(Visit(stmt->cond()));
+  RECURSE(Visit(stmt->body()));
+  store_.Forget();  // Control may transfer here via termination or 'break'.
 }
 
 
@@ -191,45 +220,65 @@ void AstTyper::VisitForStatement(ForStatement* stmt) {
   if (stmt->init() != NULL) {
     RECURSE(Visit(stmt->init()));
   }
+  store_.Forget();  // Control may transfer here via looping.
   if (stmt->cond() != NULL) {
-    RECURSE(Visit(stmt->cond()));
-
+    // Collect type feedback.
     stmt->cond()->RecordToBooleanTypeFeedback(oracle());
+
+    RECURSE(Visit(stmt->cond()));
   }
   RECURSE(Visit(stmt->body()));
+  store_.Forget();  // Control may transfer here via 'continue'.
   if (stmt->next() != NULL) {
     RECURSE(Visit(stmt->next()));
   }
+  store_.Forget();  // Control may transfer here via termination or 'break'.
 }
 
 
 void AstTyper::VisitForInStatement(ForInStatement* stmt) {
+  // Collect type feedback.
+  stmt->RecordTypeFeedback(oracle());
+
   RECURSE(Visit(stmt->enumerable()));
+  store_.Forget();  // Control may transfer here via looping or 'continue'.
   RECURSE(Visit(stmt->body()));
-
-  stmt->RecordTypeFeedback(oracle());
+  store_.Forget();  // Control may transfer here via 'break'.
 }
 
 
 void AstTyper::VisitForOfStatement(ForOfStatement* stmt) {
   RECURSE(Visit(stmt->iterable()));
+  store_.Forget();  // Control may transfer here via looping or 'continue'.
   RECURSE(Visit(stmt->body()));
+  store_.Forget();  // Control may transfer here via 'break'.
 }
 
 
 void AstTyper::VisitTryCatchStatement(TryCatchStatement* stmt) {
+  Effects try_effects = EnterEffects();
   RECURSE(Visit(stmt->try_block()));
+  ExitEffects();
+  Effects catch_effects = EnterEffects();
+  store_.Forget();  // Control may transfer here via 'throw'.
   RECURSE(Visit(stmt->catch_block()));
+  ExitEffects();
+  try_effects.Alt(catch_effects);
+  store_.Seq(try_effects);
+  // At this point, only variables that were reassigned in the catch block are
+  // still remembered.
 }
 
 
 void AstTyper::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
   RECURSE(Visit(stmt->try_block()));
+  store_.Forget();  // Control may transfer here via 'throw'.
   RECURSE(Visit(stmt->finally_block()));
 }
 
 
 void AstTyper::VisitDebuggerStatement(DebuggerStatement* stmt) {
+  store_.Forget();  // May do whatever.
 }
 
 
@@ -242,11 +291,18 @@ void AstTyper::VisitSharedFunctionInfoLiteral(SharedFunctionInfoLiteral* expr) {
 
 
 void AstTyper::VisitConditional(Conditional* expr) {
+  // Collect type feedback.
+  expr->condition()->RecordToBooleanTypeFeedback(oracle());
+
   RECURSE(Visit(expr->condition()));
+  Effects then_effects = EnterEffects();
   RECURSE(Visit(expr->then_expression()));
+  ExitEffects();
+  Effects else_effects = EnterEffects();
   RECURSE(Visit(expr->else_expression()));
-
-  expr->condition()->RecordToBooleanTypeFeedback(oracle());
+  ExitEffects();
+  then_effects.Alt(else_effects);
+  store_.Seq(then_effects);
 
   NarrowType(expr, Bounds::Either(
       expr->then_expression()->bounds(),
@@ -255,7 +311,10 @@ void AstTyper::VisitConditional(Conditional* expr) {
 
 
 void AstTyper::VisitVariableProxy(VariableProxy* expr) {
-  // TODO(rossberg): typing of variables
+  Variable* var = expr->var();
+  if (var->IsStackAllocated()) {
+    NarrowType(expr, store_.LookupBounds(variable_index(var)));
+  }
 }
 
 
@@ -274,8 +333,8 @@ void AstTyper::VisitObjectLiteral(ObjectLiteral* expr) {
   ZoneList<ObjectLiteral::Property*>* properties = expr->properties();
   for (int i = 0; i < properties->length(); ++i) {
     ObjectLiteral::Property* prop = properties->at(i);
-    RECURSE(Visit(prop->value()));
 
+    // Collect type feedback.
     if ((prop->kind() == ObjectLiteral::Property::MATERIALIZED_LITERAL &&
         !CompileTimeValue::IsCompileTimeValue(prop->value())) ||
         prop->kind() == ObjectLiteral::Property::COMPUTED) {
@@ -283,6 +342,8 @@ void AstTyper::VisitObjectLiteral(ObjectLiteral* expr) {
         prop->RecordTypeFeedback(oracle());
       }
     }
+
+    RECURSE(Visit(prop->value()));
   }
 
   NarrowType(expr, Bounds(Type::Object(), isolate_));
@@ -303,8 +364,7 @@ void AstTyper::VisitArrayLiteral(ArrayLiteral* expr) {
 void AstTyper::VisitAssignment(Assignment* expr) {
   // TODO(rossberg): Can we clean this up?
   if (expr->is_compound()) {
-    RECURSE(Visit(expr->binary_operation()));
-
+    // Collect type feedback.
     Expression* target = expr->target();
     Property* prop = target->AsProperty();
     if (prop != NULL) {
@@ -314,18 +374,27 @@ void AstTyper::VisitAssignment(Assignment* expr) {
       }
     }
 
+    RECURSE(Visit(expr->binary_operation()));
+
     NarrowType(expr, expr->binary_operation()->bounds());
   } else {
-    RECURSE(Visit(expr->target()));
-    RECURSE(Visit(expr->value()));
-
+    // Collect type feedback.
     if (expr->target()->AsProperty()) {
       expr->RecordTypeFeedback(oracle(), zone());
     }
 
+    RECURSE(Visit(expr->target()));
+    RECURSE(Visit(expr->value()));
+
     NarrowType(expr, expr->value()->bounds());
   }
-  // TODO(rossberg): handle target variables
+
+  if (expr->target()->AsVariableProxy()) {
+    Variable* var = expr->target()->AsVariableProxy()->var();
+    if (var->IsStackAllocated()) {
+      store_.Seq(variable_index(var), Effect(expr->bounds()));
+    }
+  }
 }
 
 
@@ -333,35 +402,31 @@ void AstTyper::VisitYield(Yield* expr) {
   RECURSE(Visit(expr->generator_object()));
   RECURSE(Visit(expr->expression()));
 
-  // We don't know anything about the type.
+  // We don't know anything about the result type.
 }
 
 
 void AstTyper::VisitThrow(Throw* expr) {
   RECURSE(Visit(expr->exception()));
+  // TODO(rossberg): is it worth having a non-termination effect?
 
   NarrowType(expr, Bounds(Type::None(), isolate_));
 }
 
 
 void AstTyper::VisitProperty(Property* expr) {
+  // Collect type feedback.
+  expr->RecordTypeFeedback(oracle(), zone());
+
   RECURSE(Visit(expr->obj()));
   RECURSE(Visit(expr->key()));
 
-  expr->RecordTypeFeedback(oracle(), zone());
-
-  // We don't know anything about the type.
+  // We don't know anything about the result type.
 }
 
 
 void AstTyper::VisitCall(Call* expr) {
-  RECURSE(Visit(expr->expression()));
-  ZoneList<Expression*>* args = expr->arguments();
-  for (int i = 0; i < args->length(); ++i) {
-    Expression* arg = args->at(i);
-    RECURSE(Visit(arg));
-  }
-
+  // Collect type feedback.
   Expression* callee = expr->expression();
   Property* prop = callee->AsProperty();
   if (prop != NULL) {
@@ -371,11 +436,26 @@ void AstTyper::VisitCall(Call* expr) {
     expr->RecordTypeFeedback(oracle(), CALL_AS_FUNCTION);
   }
 
-  // We don't know anything about the type.
+  RECURSE(Visit(expr->expression()));
+  ZoneList<Expression*>* args = expr->arguments();
+  for (int i = 0; i < args->length(); ++i) {
+    Expression* arg = args->at(i);
+    RECURSE(Visit(arg));
+  }
+
+  VariableProxy* proxy = expr->expression()->AsVariableProxy();
+  if (proxy != NULL && proxy->var()->is_possibly_eval(isolate())) {
+    store_.Forget();  // Eval could do whatever to local variables.
+  }
+
+  // We don't know anything about the result type.
 }
 
 
 void AstTyper::VisitCallNew(CallNew* expr) {
+  // Collect type feedback.
+  expr->RecordTypeFeedback(oracle());
+
   RECURSE(Visit(expr->expression()));
   ZoneList<Expression*>* args = expr->arguments();
   for (int i = 0; i < args->length(); ++i) {
@@ -383,9 +463,7 @@ void AstTyper::VisitCallNew(CallNew* expr) {
     RECURSE(Visit(arg));
   }
 
-  expr->RecordTypeFeedback(oracle());
-
-  // We don't know anything about the type.
+  // We don't know anything about the result type.
 }
 
 
@@ -396,13 +474,11 @@ void AstTyper::VisitCallRuntime(CallRuntime* expr) {
     RECURSE(Visit(arg));
   }
 
-  // We don't know anything about the type.
+  // We don't know anything about the result type.
 }
 
 
 void AstTyper::VisitUnaryOperation(UnaryOperation* expr) {
-  RECURSE(Visit(expr->expression()));
-
   // Collect type feedback.
   Handle<Type> op_type = oracle()->UnaryType(expr->UnaryOperationFeedbackId());
   NarrowLowerType(expr->expression(), op_type);
@@ -411,6 +487,8 @@ void AstTyper::VisitUnaryOperation(UnaryOperation* expr) {
     expr->expression()->RecordToBooleanTypeFeedback(oracle());
   }
 
+  RECURSE(Visit(expr->expression()));
+
   switch (expr->op()) {
     case Token::NOT:
     case Token::DELETE:
@@ -439,22 +517,27 @@ void AstTyper::VisitUnaryOperation(UnaryOperation* expr) {
 
 
 void AstTyper::VisitCountOperation(CountOperation* expr) {
-  RECURSE(Visit(expr->expression()));
-
+  // Collect type feedback.
   expr->RecordTypeFeedback(oracle(), zone());
   Property* prop = expr->expression()->AsProperty();
   if (prop != NULL) {
     prop->RecordTypeFeedback(oracle(), zone());
   }
 
+  RECURSE(Visit(expr->expression()));
+
   NarrowType(expr, Bounds(Type::Smi(), Type::Number(), isolate_));
+
+  if (expr->expression()->AsVariableProxy()) {
+    Variable* var = expr->expression()->AsVariableProxy()->var();
+    if (var->IsStackAllocated()) {
+      store_.Seq(variable_index(var), Effect(expr->bounds()));
+    }
+  }
 }
 
 
 void AstTyper::VisitBinaryOperation(BinaryOperation* expr) {
-  RECURSE(Visit(expr->left()));
-  RECURSE(Visit(expr->right()));
-
   // Collect type feedback.
   Handle<Type> type, left_type, right_type;
   Maybe<int> fixed_right_arg;
@@ -470,15 +553,29 @@ void AstTyper::VisitBinaryOperation(BinaryOperation* expr) {
 
   switch (expr->op()) {
     case Token::COMMA:
+      RECURSE(Visit(expr->left()));
+      RECURSE(Visit(expr->right()));
       NarrowType(expr, expr->right()->bounds());
       break;
     case Token::OR:
-    case Token::AND:
+    case Token::AND: {
+      Effects left_effects = EnterEffects();
+      RECURSE(Visit(expr->left()));
+      ExitEffects();
+      Effects right_effects = EnterEffects();
+      RECURSE(Visit(expr->right()));
+      ExitEffects();
+      left_effects.Alt(right_effects);
+      store_.Seq(left_effects);
+
       NarrowType(expr, Bounds::Either(
           expr->left()->bounds(), expr->right()->bounds(), isolate_));
       break;
+    }
     case Token::BIT_OR:
     case Token::BIT_AND: {
+      RECURSE(Visit(expr->left()));
+      RECURSE(Visit(expr->right()));
       Type* upper = Type::Union(
           expr->left()->bounds().upper, expr->right()->bounds().upper);
       if (!upper->Is(Type::Signed32())) upper = Type::Signed32();
@@ -488,12 +585,18 @@ void AstTyper::VisitBinaryOperation(BinaryOperation* expr) {
     case Token::BIT_XOR:
     case Token::SHL:
     case Token::SAR:
+      RECURSE(Visit(expr->left()));
+      RECURSE(Visit(expr->right()));
       NarrowType(expr, Bounds(Type::Smi(), Type::Signed32(), isolate_));
       break;
     case Token::SHR:
+      RECURSE(Visit(expr->left()));
+      RECURSE(Visit(expr->right()));
       NarrowType(expr, Bounds(Type::Smi(), Type::Unsigned32(), isolate_));
       break;
     case Token::ADD: {
+      RECURSE(Visit(expr->left()));
+      RECURSE(Visit(expr->right()));
       Bounds l = expr->left()->bounds();
       Bounds r = expr->right()->bounds();
       Type* lower =
@@ -513,6 +616,8 @@ void AstTyper::VisitBinaryOperation(BinaryOperation* expr) {
     case Token::MUL:
     case Token::DIV:
     case Token::MOD:
+      RECURSE(Visit(expr->left()));
+      RECURSE(Visit(expr->right()));
       NarrowType(expr, Bounds(Type::Smi(), Type::Number(), isolate_));
       break;
     default:
@@ -522,9 +627,6 @@ void AstTyper::VisitBinaryOperation(BinaryOperation* expr) {
 
 
 void AstTyper::VisitCompareOperation(CompareOperation* expr) {
-  RECURSE(Visit(expr->left()));
-  RECURSE(Visit(expr->right()));
-
   // Collect type feedback.
   Handle<Type> left_type, right_type, combined_type;
   oracle()->CompareType(expr->CompareOperationFeedbackId(),
@@ -533,6 +635,9 @@ void AstTyper::VisitCompareOperation(CompareOperation* expr) {
   NarrowLowerType(expr->right(), right_type);
   expr->set_combined_type(combined_type);
 
+  RECURSE(Visit(expr->left()));
+  RECURSE(Visit(expr->right()));
+
   NarrowType(expr, Bounds(Type::Boolean(), isolate_));
 }