Extend JSBuiltinReducer to cover Math.abs as well.

src/compiler/js-builtin-reducer.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/graph-inl.h"
 #include "src/compiler/js-builtin-reducer.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties-inl.h"
 #include "src/types.h"
 
@@ skipping 77 matching lines @@
     DCHECK_LT(index, GetJSCallArity());
     // Skip first (i.e. callee) and second (i.e. receiver) operand.
     return NodeProperties::GetValueInput(node_, index + 2);
   }
 
  private:
   Node* node_;
 };
 
 
+// ECMA-262, section 15.8.2.1.
+Reduction JSBuiltinReducer::ReduceMathAbs(Node* node) {
+  JSCallReduction r(node);
+  if (r.InputsMatchOne(Type::Unsigned32())) {
+    // Math.abs(a:uint32) -> a
+    return Replace(r.left());
+  }
+  if (r.InputsMatchOne(Type::Number())) {
+    // Math.abs(a:number) -> (a > 0 ? a : 0 - a)
+    Node* value = r.left();
+    Node* zero = jsgraph()->ZeroConstant();
+    Node* control = graph()->start();
+    Node* tag = graph()->NewNode(simplified()->NumberLessThan(), zero, value);
+
+    Node* branch = graph()->NewNode(common()->Branch(), tag, control);
+    Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+    Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+    Node* merge = graph()->NewNode(common()->Merge(2), if_true, if_false);
+
+    Node* neg = graph()->NewNode(simplified()->NumberSubtract(), zero, value);
+    value = graph()->NewNode(common()->Phi(kMachNone, 2), value, neg, merge);
+    return Replace(value);
+  }
+  return NoChange();
+}
+
+
 // ECMA-262, section 15.8.2.17.
 Reduction JSBuiltinReducer::ReduceMathSqrt(Node* node) {
   JSCallReduction r(node);
   if (r.InputsMatchOne(Type::Number())) {
     // Math.sqrt(a:number) -> Float64Sqrt(a)
     Node* value = graph()->NewNode(machine()->Float64Sqrt(), r.left());
     return Replace(value);
   }
   return NoChange();
 }
@@ skipping 55 matching lines @@
   return NoChange();
 }
 
 
 Reduction JSBuiltinReducer::Reduce(Node* node) {
   JSCallReduction r(node);
 
   // Dispatch according to the BuiltinFunctionId if present.
   if (!r.HasBuiltinFunctionId()) return NoChange();
   switch (r.GetBuiltinFunctionId()) {
+    case kMathAbs:
+      return ReplaceWithPureReduction(node, ReduceMathAbs(node));
     case kMathSqrt:
       return ReplaceWithPureReduction(node, ReduceMathSqrt(node));
     case kMathMax:
       return ReplaceWithPureReduction(node, ReduceMathMax(node));
     case kMathImul:
       return ReplaceWithPureReduction(node, ReduceMathImul(node));
     case kMathFround:
       return ReplaceWithPureReduction(node, ReduceMathFround(node));
     default:
       break;
   }
   return NoChange();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8