Ensure only whitelisted stubs have sse2 versions in the snapshot.

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 453 matching lines @@
 //     // 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) {
+    if (Check(f, cross_compile_)) return true;
     ASSERT(initialized_);
     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 == SAHF && !FLAG_enable_sahf) return false;
-    return (supported_ & (static_cast<uint64_t>(1) << f)) != 0;
+    return Check(f, supported_);
   }
 
   static bool IsFoundByRuntimeProbingOnly(CpuFeature f) {
     ASSERT(initialized_);
-    return (found_by_runtime_probing_only_ &
-            (static_cast<uint64_t>(1) << f)) != 0;
+    return Check(f, found_by_runtime_probing_only_);
   }
 
   static bool IsSafeForSnapshot(CpuFeature f) {
-    return (IsSupported(f) &&
+    return Check(f, cross_compile_) ||
+           (IsSupported(f) &&
             (!Serializer::enabled() || !IsFoundByRuntimeProbingOnly(f)));
   }
 
+  static bool VerifyCrossCompiling() {
+    return cross_compile_ == 0;
+  }
+
+  static bool VerifyCrossCompiling(CpuFeature f) {
+    uint64_t mask = flag2set(f);
+    return cross_compile_ == 0 ||
+           (cross_compile_ & mask) == mask;
+  }
+
  private:
+  static bool Check(CpuFeature f, uint64_t set) {
+    return (set & flag2set(f)) != 0;
+  }
+
+  static uint64_t flag2set(CpuFeature f) {
+    return static_cast<uint64_t>(1) << f;
+  }
+
   // 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 << CMOV);
 
 #ifdef DEBUG
   static bool initialized_;
 #endif
   static uint64_t supported_;
   static uint64_t found_by_runtime_probing_only_;
 
+  static uint64_t cross_compile_;
+
   friend class ExternalReference;
   friend class PlatformFeatureScope;
   DISALLOW_COPY_AND_ASSIGN(CpuFeatures);
 };
 
 
 class Assembler : public AssemblerBase {
  private:
   // We check before assembling an instruction that there is sufficient
   // space to write an instruction and its relocation information.
@@ skipping 1144 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_