Improve handling of unary plus.

Simple strategy: Transform unary plus into multiplication by one directly in the
parser and remove it from the Hydrogen graph later. This gives correct type
feedback without any special stub for it.

BUG=v8:2527

Review URL: https://codereview.chromium.org/13902013

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14306 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/full-codegen-arm.cc

@@ -3976,18 +3976,6 @@ void FullCodeGenerator::VisitUnaryOperation(UnaryOperation* expr) {
       break;
     }
 
-    case Token::ADD: {
-      Comment cmt(masm_, "[ UnaryOperation (ADD)");
-      VisitForAccumulatorValue(expr->expression());
-      Label no_conversion;
-      __ JumpIfSmi(result_register(), &no_conversion);
-      ToNumberStub convert_stub;
-      __ CallStub(&convert_stub);
-      __ bind(&no_conversion);
-      context()->Plug(result_register());
-      break;
-    }
-
     case Token::SUB:
       EmitUnaryOperation(expr, "[ UnaryOperation (SUB)");
       break;

src/hydrogen-instructions.cc

@@ -1436,6 +1436,21 @@ HValue* HSub::Canonicalize() {
 }
 
 
+// TODO(svenpanne) Use this in other Canonicalize() functions.
+static bool IsIdentityOperation(HValue* arg1, HValue* arg2, int32_t identity) {
+  return arg1->representation().IsSpecialization() &&
+      arg2->IsInteger32Constant() &&
+      arg2->GetInteger32Constant() == identity;
+}
+
+
+HValue* HMul::Canonicalize() {
+  if (IsIdentityOperation(left(), right(), 1)) return left();
+  if (IsIdentityOperation(right(), left(), 1)) return right();
+  return this;
+}
+
+
 HValue* HChange::Canonicalize() {
   return (from().Equals(to())) ? value() : this;
 }

src/hydrogen-instructions.h

@@ -4401,6 +4401,8 @@ class HMul: public HArithmeticBinaryOperation {
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
 
+  virtual HValue* Canonicalize();
+
   // Only commutative if it is certain that not two objects are multiplicated.
   virtual bool IsCommutative() const {
     return !representation().IsTagged();

src/hydrogen.cc

@@ -9160,7 +9160,6 @@ void HOptimizedGraphBuilder::VisitUnaryOperation(UnaryOperation* expr) {
     case Token::DELETE: return VisitDelete(expr);
     case Token::VOID: return VisitVoid(expr);
     case Token::TYPEOF: return VisitTypeof(expr);
-    case Token::ADD: return VisitAdd(expr);
     case Token::SUB: return VisitSub(expr);
     case Token::BIT_NOT: return VisitBitNot(expr);
     case Token::NOT: return VisitNot(expr);
@@ -9218,21 +9217,6 @@ void HOptimizedGraphBuilder::VisitTypeof(UnaryOperation* expr) {
 }
 
 
-void HOptimizedGraphBuilder::VisitAdd(UnaryOperation* expr) {
-  CHECK_ALIVE(VisitForValue(expr->expression()));
-  HValue* value = Pop();
-  HValue* context = environment()->LookupContext();
-  HInstruction* instr =
-      HMul::New(zone(), context, value, graph()->GetConstant1());
-  if (instr->IsBinaryOperation()) {
-    // Since we don't have type feedback, we must be cautious/pessimistic.
-    HBinaryOperation::cast(instr)->set_observed_input_representation(
-        Representation::Tagged(), Representation::Tagged());
-  }
-  return ast_context()->ReturnInstruction(instr, expr->id());
-}
-
-
 void HOptimizedGraphBuilder::VisitSub(UnaryOperation* expr) {
   CHECK_ALIVE(VisitForValue(expr->expression()));
   HValue* value = Pop();

src/hydrogen.h

@@ -1267,7 +1267,6 @@ class HOptimizedGraphBuilder: public HGraphBuilder, public AstVisitor {
   void VisitDelete(UnaryOperation* expr);
   void VisitVoid(UnaryOperation* expr);
   void VisitTypeof(UnaryOperation* expr);
-  void VisitAdd(UnaryOperation* expr);
   void VisitSub(UnaryOperation* expr);
   void VisitBitNot(UnaryOperation* expr);
   void VisitNot(UnaryOperation* expr);

src/ia32/full-codegen-ia32.cc

@@ -3967,18 +3967,6 @@ void FullCodeGenerator::VisitUnaryOperation(UnaryOperation* expr) {
       break;
     }
 
-    case Token::ADD: {
-      Comment cmt(masm_, "[ UnaryOperation (ADD)");
-      VisitForAccumulatorValue(expr->expression());
-      Label no_conversion;
-      __ JumpIfSmi(result_register(), &no_conversion);
-      ToNumberStub convert_stub;
-      __ CallStub(&convert_stub);
-      __ bind(&no_conversion);
-      context()->Plug(result_register());
-      break;
-    }
-
     case Token::SUB:
       EmitUnaryOperation(expr, "[ UnaryOperation (SUB)");
       break;

src/mips/full-codegen-mips.cc

@@ -3995,19 +3995,6 @@ void FullCodeGenerator::VisitUnaryOperation(UnaryOperation* expr) {
       break;
     }
 
-    case Token::ADD: {
-      Comment cmt(masm_, "[ UnaryOperation (ADD)");
-      VisitForAccumulatorValue(expr->expression());
-      Label no_conversion;
-      __ JumpIfSmi(result_register(), &no_conversion);
-      __ mov(a0, result_register());
-      ToNumberStub convert_stub;
-      __ CallStub(&convert_stub);
-      __ bind(&no_conversion);
-      context()->Plug(result_register());
-      break;
-    }
-
     case Token::SUB:
       EmitUnaryOperation(expr, "[ UnaryOperation (SUB)");
       break;

src/parser.cc

@@ -3286,6 +3286,16 @@ Expression* Parser::ParseUnaryExpression(bool* ok) {
       }
     }
 
+    // Desugar '+foo' into 'foo*1', this enables the collection of type feedback
+    // without any special stub and the multiplication is removed later in
+    // Crankshaft's canonicalization pass.
+    if (op == Token::ADD) {
+      return factory()->NewBinaryOperation(Token::MUL,
+                                           expression,
+                                           factory()->NewNumberLiteral(1),
+                                           position);
+    }
+
     return factory()->NewUnaryOperation(op, expression, position);
 
   } else if (Token::IsCountOp(op)) {

src/x64/full-codegen-x64.cc

@@ -3968,18 +3968,6 @@ void FullCodeGenerator::VisitUnaryOperation(UnaryOperation* expr) {
       break;
     }
 
-    case Token::ADD: {
-      Comment cmt(masm_, "[ UnaryOperation (ADD)");
-      VisitForAccumulatorValue(expr->expression());
-      Label no_conversion;
-      __ JumpIfSmi(result_register(), &no_conversion);
-      ToNumberStub convert_stub;
-      __ CallStub(&convert_stub);
-      __ bind(&no_conversion);
-      context()->Plug(result_register());
-      break;
-    }
-
     case Token::SUB:
       EmitUnaryOperation(expr, "[ UnaryOperation (SUB)");
       break;