PPC: perf enhancement: omit redundant compare with 0

src/ppc/constants-ppc.h

 // 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.
 
 #ifndef V8_PPC_CONSTANTS_PPC_H_
 #define V8_PPC_CONSTANTS_PPC_H_
 
 namespace v8 {
 namespace internal {
 
@@ skipping 318 matching lines @@
   // Instruction bit masks
   kCondMask = 0x1F << 21,
   kOff12Mask = (1 << 12) - 1,
   kImm24Mask = (1 << 24) - 1,
   kOff16Mask = (1 << 16) - 1,
   kImm16Mask = (1 << 16) - 1,
   kImm26Mask = (1 << 26) - 1,
   kBOfieldMask = 0x1f << 21,
   kOpcodeMask = 0x3f << 26,
   kExt1OpcodeMask = 0x3ff << 1,
-  kExt2OpcodeMask = 0x1f << 1,
+  kExt2OpcodeMask = 0x3ff << 1,
+  kExt2OpcodeVariant2Mask = 0x1ff << 2,
   kExt5OpcodeMask = 0x3 << 2,
   kBOMask = 0x1f << 21,
   kBIMask = 0x1F << 16,
   kBDMask = 0x14 << 2,
   kAAMask = 0x01 << 1,
   kLKMask = 0x01,
   kRCMask = 0x01,
   kTOMask = 0x1f << 21
 };
 
@@ skipping 232 matching lines @@
   // Lookup the register number for the name provided.
   static int Number(const char* name);
 
  private:
   static const char* names_[kNumFPRegisters];
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_PPC_CONSTANTS_PPC_H_