Remove SSE2 feature checks from x64 code (it is always on)

src/x64/assembler-x64.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 430 matching lines @@
 };
 
 
 // CpuFeatures keeps track of which features are supported by the target CPU.
 // Supported features must be enabled by a CpuFeatureScope before use.
 // Example:
 //   if (assembler->IsSupported(SSE3)) {
 //     CpuFeatureScope fscope(assembler, SSE3);
 //     // Generate SSE3 floating point code.
 //   } else {
-//     // Generate standard x87 or SSE2 floating point code.
+//     // Generate standard SSE2 floating point code.
 //   }
 class CpuFeatures : public AllStatic {
  public:
   // Detect features of the target CPU. Set safe defaults if the serializer
   // is enabled (snapshots must be portable).
   static void Probe();
 
   // Check whether a feature is supported by the target CPU.
   static bool IsSupported(CpuFeature f) {
     ASSERT(initialized_);
-    if (f == SSE2 && !FLAG_enable_sse2) return false;
     if (f == SSE3 && !FLAG_enable_sse3) return false;
     if (f == SSE4_1 && !FLAG_enable_sse4_1) return false;
     if (f == CMOV && !FLAG_enable_cmov) return false;
     if (f == RDTSC && !FLAG_enable_rdtsc) return false;
     if (f == SAHF && !FLAG_enable_sahf) return false;
     return (supported_ & (static_cast<uint64_t>(1) << f)) != 0;
   }
 
   static bool IsFoundByRuntimeProbingOnly(CpuFeature f) {
     ASSERT(initialized_);
     return (found_by_runtime_probing_only_ &
             (static_cast<uint64_t>(1) << f)) != 0;
   }
 
   static bool IsSafeForSnapshot(CpuFeature f) {
     return (IsSupported(f) &&
             (!Serializer::enabled() || !IsFoundByRuntimeProbingOnly(f)));
   }
 
  private:
-  // Safe defaults include SSE2 and CMOV for X64. It is always available, if
+  // Safe defaults include CMOV for X64. It is always available, if
   // anyone checks, but they shouldn't need to check.
   // The required user mode extensions in X64 are (from AMD64 ABI Table A.1):
   //   fpu, tsc, cx8, cmov, mmx, sse, sse2, fxsr, syscall
-  static const uint64_t kDefaultCpuFeatures = (1 << SSE2 | 1 << CMOV);
+  static const uint64_t kDefaultCpuFeatures = (1 << CMOV);
 
 #ifdef DEBUG
   static bool initialized_;
 #endif
   static uint64_t supported_;
   static uint64_t found_by_runtime_probing_only_;
 
   friend class ExternalReference;
   DISALLOW_COPY_AND_ASSIGN(CpuFeatures);
 };
@@ skipping 1138 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_