message: [Cocoa] Prefer llvm::SignExtend64. Pointed out by zturner.
diff: @@ -773,8 +773,7 @@ static uint64_t decodeExponent(uint64_t exp) {
  int64_t exp7 = exp;
  // Tagged exponent field is 7-bit signed. Sign-extend the value to 64 bits
  // before performing arithmetic.
  - int64_t exp11 = ((exp7 << 57) >> 57) + TAGGED_DATE_EXPONENT_BIAS;
  - return exp11;
  + return llvm::SignExtend64<7>(exp) + TAGGED_DATE_EXPONENT_BIAS;
  }
  static uint64_t decodeTaggedTimeInterval(uint64_t encodedTimeInterval) {
  