Cleaned up CpuFeature scope handling.

src/x64/assembler-x64.h

Index: src/x64/assembler-x64.h
diff --git a/src/x64/assembler-x64.h b/src/x64/assembler-x64.h
index 69eeb8e7add80862b700a9d1210403f6a6deaa40..86ae057abbe2a562c9ed894a2f244d4d6ea7bc57 100644
--- a/src/x64/assembler-x64.h
+++ b/src/x64/assembler-x64.h
@@ -442,10 +442,10 @@ class Operand BASE_EMBEDDED {
 
 
 // CpuFeatures keeps track of which features are supported by the target CPU.
-// Supported features must be enabled by a Scope before use.
+// Supported features must be enabled by a CpuFeatureScope before use.
 // Example:
-//   if (CpuFeatures::IsSupported(SSE3)) {
-//     CpuFeatures::Scope fscope(SSE3);
+//   if (assembler->IsSupported(SSE3)) {
+//     CpuFeatureScope fscope(assembler, SSE3);
 //     // Generate SSE3 floating point code.
 //   } else {
 //     // Generate standard x87 or SSE2 floating point code.
@@ -465,57 +465,14 @@ class CpuFeatures : public AllStatic {
     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_ & (V8_UINT64_C(1) << f)) != 0;
+    return (supported_ & (static_cast<uint64_t>(1) << f)) != 0;
   }
 
-#ifdef DEBUG
-  // Check whether a feature is currently enabled.
-  static bool IsEnabled(CpuFeature f) {
+  static bool IsFoundByRuntimeProbingOnly(CpuFeature f) {
     ASSERT(initialized_);
-    Isolate* isolate = Isolate::UncheckedCurrent();
-    if (isolate == NULL) {
-      // When no isolate is available, work as if we're running in
-      // release mode.
-      return IsSupported(f);
-    }
-    uint64_t enabled = isolate->enabled_cpu_features();
-    return (enabled & (V8_UINT64_C(1) << f)) != 0;
+    return (found_by_runtime_probing_only_ &
+            (static_cast<uint64_t>(1) << f)) != 0;
   }
-#endif
-
-  // Enable a specified feature within a scope.
-  class Scope BASE_EMBEDDED {
-#ifdef DEBUG
-
-   public:
-    explicit Scope(CpuFeature f) {
-      uint64_t mask = V8_UINT64_C(1) << f;
-      ASSERT(CpuFeatures::IsSupported(f));
-      ASSERT(!Serializer::enabled() ||
-             (CpuFeatures::found_by_runtime_probing_ & mask) == 0);
-      isolate_ = Isolate::UncheckedCurrent();
-      old_enabled_ = 0;
-      if (isolate_ != NULL) {
-        old_enabled_ = isolate_->enabled_cpu_features();
-        isolate_->set_enabled_cpu_features(old_enabled_ | mask);
-      }
-    }
-    ~Scope() {
-      ASSERT_EQ(Isolate::UncheckedCurrent(), isolate_);
-      if (isolate_ != NULL) {
-        isolate_->set_enabled_cpu_features(old_enabled_);
-      }
-    }
-
-   private:
-    Isolate* isolate_;
-    uint64_t old_enabled_;
-#else
-
-   public:
-    explicit Scope(CpuFeature f) {}
-#endif
-  };
 
  private:
   // Safe defaults include SSE2 and CMOV for X64. It is always available, if
@@ -528,7 +485,7 @@ class CpuFeatures : public AllStatic {
   static bool initialized_;
 #endif
   static uint64_t supported_;
-  static uint64_t found_by_runtime_probing_;
+  static uint64_t found_by_runtime_probing_only_;
 
   friend class ExternalReference;
   DISALLOW_COPY_AND_ASSIGN(CpuFeatures);