[turbofan] Improve testability of the InstructionSelector.

src/assembler.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 158 matching lines @@
 //   }
 class CpuFeatures : public AllStatic {
  public:
   static void Probe(bool cross_compile) {
     STATIC_ASSERT(NUMBER_OF_CPU_FEATURES <= kBitsPerInt);
     if (initialized_) return;
     initialized_ = true;
     ProbeImpl(cross_compile);
   }
 
+  static unsigned SupportedFeatures() {
+    Probe(false);
+    return supported_;
+  }
+
   static bool IsSupported(CpuFeature f) {
     return (supported_ & (1u << f)) != 0;
   }
 
   static inline bool SupportsCrankshaft();
 
   static inline unsigned cache_line_size() {
     DCHECK(cache_line_size_ != 0);
     return cache_line_size_;
   }
@@ skipping 931 matching lines @@
 
  private:
   int32_t multiplier_;
   int32_t shift_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ASSEMBLER_H_