PPC: Match -0 - x with sign bit flip.

src/compiler/ppc/instruction-selector-ppc.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/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 891 matching lines @@
 }
 
 
 void InstructionSelector::VisitFloat64Add(Node* node) {
   // TODO(mbrandy): detect multiply-add
   VisitRRR(this, kPPC_AddDouble, node);
 }
 
 
 void InstructionSelector::VisitFloat32Sub(Node* node) {
+  PPCOperandGenerator g(this);
+  Float32BinopMatcher m(node);
+  if (m.left().IsMinusZero()) {
+    Emit(kPPC_NegDouble, g.DefineAsRegister(node),
+         g.UseRegister(m.right().node()));
+    return;
+  }
   VisitRRR(this, kPPC_SubDouble, node);
 }
 
 
 void InstructionSelector::VisitFloat64Sub(Node* node) {
   // TODO(mbrandy): detect multiply-subtract
   PPCOperandGenerator g(this);
   Float64BinopMatcher m(node);
-  if (m.left().IsMinusZero() && m.right().IsFloat64RoundDown() &&
-      CanCover(m.node(), m.right().node())) {
-    if (m.right().InputAt(0)->opcode() == IrOpcode::kFloat64Sub &&
-        CanCover(m.right().node(), m.right().InputAt(0))) {
-      Float64BinopMatcher mright0(m.right().InputAt(0));
-      if (mright0.left().IsMinusZero()) {
-        // -floor(-x) = ceil(x)
-        Emit(kPPC_CeilDouble, g.DefineAsRegister(node),
-             g.UseRegister(mright0.right().node()));
-        return;
+  if (m.left().IsMinusZero()) {
+    if (m.right().IsFloat64RoundDown() &&
+        CanCover(m.node(), m.right().node())) {
+      if (m.right().InputAt(0)->opcode() == IrOpcode::kFloat64Sub &&
+          CanCover(m.right().node(), m.right().InputAt(0))) {
+        Float64BinopMatcher mright0(m.right().InputAt(0));
+        if (mright0.left().IsMinusZero()) {
+          // -floor(-x) = ceil(x)
+          Emit(kPPC_CeilDouble, g.DefineAsRegister(node),
+               g.UseRegister(mright0.right().node()));
+          return;
+        }
       }
     }
+    Emit(kPPC_NegDouble, g.DefineAsRegister(node),
+         g.UseRegister(m.right().node()));
+    return;
   }
   VisitRRR(this, kPPC_SubDouble, node);
 }
 
 
 void InstructionSelector::VisitFloat32Mul(Node* node) {
   VisitRRR(this, kPPC_MulDouble, node);
 }
 
 
@@ skipping 588 matching lines @@
          MachineOperatorBuilder::kFloat64Min |
          MachineOperatorBuilder::kFloat64RoundDown |
          MachineOperatorBuilder::kFloat64RoundTruncate |
          MachineOperatorBuilder::kFloat64RoundTiesAway;
   // We omit kWord32ShiftIsSafe as s[rl]w use 0x3f as a mask rather than 0x1f.
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8