[turbofan] Remove indirection in JSToBoolean/JSUnaryNot lowering.

src/compiler/js-typed-lowering.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/operator-properties.h"
@@ skipping 508 matching lines @@
   }
   if (r.BothInputsAre(Type::Number())) {
     return r.ChangeToPureOperator(simplified()->NumberEqual(), invert);
   }
   // TODO(turbofan): js-typed-lowering of StrictEqual(mixed types)
   return NoChange();
 }
 
 
 Reduction JSTypedLowering::ReduceJSUnaryNot(Node* node) {
-  Node* input = node->InputAt(0);
-  Type* input_type = NodeProperties::GetBounds(input).upper;
+  Node* const input = node->InputAt(0);
+  Type* const input_type = NodeProperties::GetBounds(input).upper;
   if (input_type->Is(Type::Boolean())) {
-    // JSUnaryNot(x:boolean,context) => BooleanNot(x)
+    // JSUnaryNot(x:boolean) => BooleanNot(x)
     node->set_op(simplified()->BooleanNot());
     node->TrimInputCount(1);
     return Changed(node);
   } else if (input_type->Is(Type::OrderedNumber())) {
-    // JSUnaryNot(x:number,context) => NumberEqual(x,#0)
+    // JSUnaryNot(x:number) => NumberEqual(x,#0)
     node->set_op(simplified()->NumberEqual());
     node->ReplaceInput(1, jsgraph()->ZeroConstant());
-    DCHECK_EQ(2, node->InputCount());
+    node->TrimInputCount(2);
+    return Changed(node);
+  } else if (input_type->Is(Type::String())) {
+    // JSUnaryNot(x:string) => NumberEqual(x.length,#0)

[Michael Starzinger, 2015/03/19 10:10:54]

nit: Can we add a one-liner comment that this is safe for the load to be
effect-free (i.e. not linked into effect chain) because we assume String::length
to be immutable?

+    FieldAccess const access = AccessBuilder::ForStringLength();
+    Node* length = graph()->NewNode(simplified()->LoadField(access), input,
+                                    graph()->start(), graph()->start());
+    node->set_op(simplified()->NumberEqual());
+    node->ReplaceInput(0, length);
+    node->ReplaceInput(1, jsgraph()->ZeroConstant());
+    node->TrimInputCount(2);
+    NodeProperties::ReplaceWithValue(node, node, length);
     return Changed(node);
   }
-  // JSUnaryNot(x,context) => BooleanNot(AnyToBoolean(x))
-  node->set_op(simplified()->BooleanNot());
-  node->ReplaceInput(0, graph()->NewNode(simplified()->AnyToBoolean(), input));
-  node->TrimInputCount(1);
-  return Changed(node);
+  return NoChange();
 }
 
 
 Reduction JSTypedLowering::ReduceJSToBoolean(Node* node) {
-  Node* input = node->InputAt(0);
-  Type* input_type = NodeProperties::GetBounds(input).upper;
+  Node* const input = node->InputAt(0);
+  Type* const input_type = NodeProperties::GetBounds(input).upper;
   if (input_type->Is(Type::Boolean())) {
-    // JSToBoolean(x:boolean,context) => x
+    // JSToBoolean(x:boolean) => x
     return Replace(input);
+  } else if (input_type->Is(Type::OrderedNumber())) {
+    // JSToBoolean(x:ordered-number) => BooleanNot(NumberEqual(x,#0))
+    node->set_op(simplified()->BooleanNot());
+    node->ReplaceInput(0, graph()->NewNode(simplified()->NumberEqual(), input,
+                                           jsgraph()->ZeroConstant()));
+    node->TrimInputCount(1);
+    return Changed(node);
+  } else if (input_type->Is(Type::String())) {
+    // JSToBoolean(x:string) => NumberLessThan(#0,x.length)

[Michael Starzinger, 2015/03/19 10:10:54]

nit: Likewise about the comment.

+    FieldAccess const access = AccessBuilder::ForStringLength();
+    Node* length = graph()->NewNode(simplified()->LoadField(access), input,
+                                    graph()->start(), graph()->start());
+    node->set_op(simplified()->NumberLessThan());
+    node->ReplaceInput(0, jsgraph()->ZeroConstant());
+    node->ReplaceInput(1, length);
+    node->TrimInputCount(2);
+    return Changed(node);
   }
-  // JSToBoolean(x,context) => AnyToBoolean(x)
-  node->set_op(simplified()->AnyToBoolean());
-  node->TrimInputCount(1);
-  return Changed(node);
+  return NoChange();
 }
 
 
 Reduction JSTypedLowering::ReduceJSToNumberInput(Node* input) {
   if (input->opcode() == IrOpcode::kJSToNumber) {
     // Recursively try to reduce the input first.
     Reduction result = ReduceJSToNumber(input);
     if (result.Changed()) return result;
     return Changed(input);  // JSToNumber(JSToNumber(x)) => JSToNumber(x)
   }
@@ skipping 480 matching lines @@
 }
 
 
 MachineOperatorBuilder* JSTypedLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8