[turbofan] Transform x * -1.0 to -0.0 - x.

TEST=msjunit/asm,unittests
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/683753004

Cr-Commit-Position: refs/heads/master@{#25176}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25176 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/machine-operator-reducer.cc

@@ -441,6 +441,12 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
     }
     case IrOpcode::kFloat64Mul: {
       Float64BinopMatcher m(node);
+      if (m.right().Is(-1)) {  // x * -1.0 => -0.0 - x
+        node->set_op(machine()->Float64Sub());
+        node->ReplaceInput(0, Float64Constant(-0.0));
+        node->ReplaceInput(1, m.left().node());
+        return Changed(node);
+      }
       if (m.right().Is(1)) return Replace(m.left().node());  // x * 1.0 => x
       if (m.right().IsNaN()) {                               // x * NaN => NaN
         return Replace(m.right().node());

test/mjsunit/asm/float64mul.js

+// 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.
+
+function Module(stdlib, foreign, heap) {
+  "use asm";
+  function f1(i) {
+    i = +i;
+    return +(i * -1);
+  }
+  function f2(i) {
+    i = +i;
+    return +(-1 * i);
+  }
+  return { f1: f1, f2: f2 };
+}
+
+var m = Module(this, {}, new ArrayBuffer(64 * 1024));
+
+assertEquals(NaN, m.f1(NaN));
+assertEquals(NaN, m.f2(NaN));
+assertEquals(Infinity, 1 / m.f1(-0));
+assertEquals(Infinity, 1 / m.f2(-0));
+assertEquals(Infinity, m.f1(-Infinity));
+assertEquals(Infinity, m.f2(-Infinity));
+assertEquals(-Infinity, 1 / m.f1(0));
+assertEquals(-Infinity, 1 / m.f2(0));
+assertEquals(-Infinity, m.f1(Infinity));
+assertEquals(-Infinity, m.f2(Infinity));
+for (var i = -2147483648; i < 2147483648; i += 3999777) {
+  assertEquals(-i, m.f1(i));
+  assertEquals(-i, m.f2(i));
+}

test/unittests/compiler/machine-operator-reducer-unittest.cc

@@ -1106,6 +1106,27 @@ TEST_F(MachineOperatorReducerTest, Uint32LessThanWithWord32Sar) {
 }
 
 
+// -----------------------------------------------------------------------------
+// Float64Mul
+
+
+TEST_F(MachineOperatorReducerTest, Float64MulWithMinusOne) {
+  Node* const p0 = Parameter(0);
+  {
+    Reduction r = Reduce(
+        graph()->NewNode(machine()->Float64Mul(), p0, Float64Constant(-1.0)));
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsFloat64Sub(IsFloat64Constant(-0.0), p0));
+  }
+  {
+    Reduction r = Reduce(
+        graph()->NewNode(machine()->Float64Mul(), Float64Constant(-1.0), p0));
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsFloat64Sub(IsFloat64Constant(-0.0), p0));
+  }
+}
+
+
 // -----------------------------------------------------------------------------
 // Store
 

test/unittests/compiler/node-test-utils.cc

@@ -1040,6 +1040,7 @@ IS_BINOP_MATCHER(Int32MulHigh)
 IS_BINOP_MATCHER(Int32LessThan)
 IS_BINOP_MATCHER(Uint32LessThan)
 IS_BINOP_MATCHER(Uint32LessThanOrEqual)
+IS_BINOP_MATCHER(Float64Sub)
 #undef IS_BINOP_MATCHER
 
 

test/unittests/compiler/node-test-utils.h

@@ -156,6 +156,8 @@ Matcher<Node*> IsChangeUint32ToUint64(const Matcher<Node*>& input_matcher);
 Matcher<Node*> IsTruncateFloat64ToFloat32(const Matcher<Node*>& input_matcher);
 Matcher<Node*> IsTruncateFloat64ToInt32(const Matcher<Node*>& input_matcher);
 Matcher<Node*> IsTruncateInt64ToInt32(const Matcher<Node*>& input_matcher);
+Matcher<Node*> IsFloat64Sub(const Matcher<Node*>& lhs_matcher,
+                            const Matcher<Node*>& rhs_matcher);
 Matcher<Node*> IsFloat64Sqrt(const Matcher<Node*>& input_matcher);
 Matcher<Node*> IsFloat64Floor(const Matcher<Node*>& input_matcher);
 Matcher<Node*> IsFloat64Ceil(const Matcher<Node*>& input_matcher);