[v8-dev] Optimise Math.floor(x/y) to use integer division for specific divisor....

src/compiler-intrinsics.h

 // Copyright 2006-2008 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 22 matching lines @@
 
 class CompilerIntrinsics {
  public:
   // Returns number of zero bits preceding least significant 1 bit.
   // Undefined for zero value.
   INLINE(static int CountTrailingZeros(uint32_t value));
 
   // Returns number of zero bits following most significant 1 bit.
   // Undefined for zero value.
   INLINE(static int CountLeadingZeros(uint32_t value));
+
+  // Returns the number of bits set.
+  INLINE(static int CountSetBits(uint32_t value));
 };
 
 #ifdef __GNUC__
 int CompilerIntrinsics::CountTrailingZeros(uint32_t value) {
   return __builtin_ctz(value);
 }
 
 int CompilerIntrinsics::CountLeadingZeros(uint32_t value) {
   return __builtin_clz(value);
 }
 
+int CompilerIntrinsics::CountSetBits(uint32_t value) {
+  return __builtin_popcount(value);
+}
+
 #elif defined(_MSC_VER)
 
 #pragma intrinsic(_BitScanForward)
 #pragma intrinsic(_BitScanReverse)
 
 int CompilerIntrinsics::CountTrailingZeros(uint32_t value) {
   unsigned long result;  //NOLINT
   _BitScanForward(&result, static_cast<long>(value));  //NOLINT
   return static_cast<int>(result);
 }
 
 int CompilerIntrinsics::CountLeadingZeros(uint32_t value) {
   unsigned long result;  //NOLINT
   _BitScanReverse(&result, static_cast<long>(value));  //NOLINT
   return 31 - static_cast<int>(result);
 }
 
+int CompilerIntrinsics::CountSetBits(uint32_t value) {
+  // __popcnt is only supported from VS2008.
+#define _MSC_VER_VS2008 1500
+#if _MSC_VER >= _MSC_VER_VS2008
+  return __popcnt(value);
+#else
+  // Manually count set bits.
+  value = ((value >>  1) & 0x55555555) + (value & 0x55555555);
+  value = ((value >>  2) & 0x33333333) + (value & 0x33333333);
+  value = ((value >>  4) & 0x0f0f0f0f) + (value & 0x0f0f0f0f);
+  value = ((value >>  8) & 0x00ff00ff) + (value & 0x00ff00ff);
+  value = ((value >> 16) & 0x0000ffff) + (value & 0x0000ffff);
+  return value;
+#endif
+#undef _MSC_VER_VS2008
+}
+
 #else
 #error Unsupported compiler
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_COMPILER_INTRINSICS_H_