[Support] make countLeadingZeros() countTrailingZeros() countLeadingOnes() and countTrailingOnes() return unsigned

[shawnl]

Summary

This matches APInt's versions of these functions, and there is no need for these to be size_t.

(as well as __builtin_clzll())

[shawnl]

bugs

[rnk]

Seems fine.

[shawnl]

applied r361724

include/llvm/Support/MathExtras.h

   static_assert(std::numeric_limits<T>::is_integer &&
                     !std::numeric_limits<T>::is_signed,
                 "Only unsigned integral types are allowed.");
   return llvm::detail::TrailingZerosCounter<T, sizeof(T)>::count(Val, ZB);
 }
 
 namespace detail {
 template <typename T, std::size_t SizeOfT> struct LeadingZerosCounter {
-  static std::size_t count(T Val, ZeroBehavior) {
+  static unsigned count(T Val, ZeroBehavior) {
     if (!Val)
       return std::numeric_limits<T>::digits;
 
     // Bisection method.
     std::size_t ZeroBits = 0;
     for (T Shift = std::numeric_limits<T>::digits >> 1; Shift; Shift >>= 1) {
       T Tmp = Val >> Shift;
       if (Tmp)
         Val = Tmp;
       else
         ZeroBits |= Shift;
     }
     return ZeroBits;
   }
 };
 
 #if __GNUC__ >= 4 || defined(_MSC_VER)
 template <typename T> struct LeadingZerosCounter<T, 4> {
-  static std::size_t count(T Val, ZeroBehavior ZB) {
+  static unsigned count(T Val, ZeroBehavior ZB) {
     if (ZB != ZB_Undefined && Val == 0)
       return 32;
 
 #if __has_builtin(__builtin_clz) || LLVM_GNUC_PREREQ(4, 0, 0)
     return __builtin_clz(Val);
 #elif defined(_MSC_VER)
     unsigned long Index;
     _BitScanReverse(&Index, Val);
     return Index ^ 31;
 #endif
   }
 };
 
 #if !defined(_MSC_VER) || defined(_M_X64)
 template <typename T> struct LeadingZerosCounter<T, 8> {
-  static std::size_t count(T Val, ZeroBehavior ZB) {
+  static unsigned count(T Val, ZeroBehavior ZB) {
     if (ZB != ZB_Undefined && Val == 0)
       return 64;
 
 #if __has_builtin(__builtin_clzll) || LLVM_GNUC_PREREQ(4, 0, 0)
     return __builtin_clzll(Val);
 #elif defined(_MSC_VER)
     unsigned long Index;
     _BitScanReverse64(&Index, Val);
     return Index ^ 63;
 #endif
   }
 };
 #endif
 #endif
 } // namespace detail
 
 /// Count number of 0's from the most significant bit to the least
 ///   stopping at the first 1.
 ///
 /// Only unsigned integral types are allowed.
 ///
 /// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are
 ///   valid arguments.
 template <typename T>
-std::size_t countLeadingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
+unsigned countLeadingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
   static_assert(std::numeric_limits<T>::is_integer &&
                     !std::numeric_limits<T>::is_signed,
                 "Only unsigned integral types are allowed.");
   return llvm::detail::LeadingZerosCounter<T, sizeof(T)>::count(Val, ZB);
 }
 
 /// Get the index of the first set bit starting from the least
 ///   significant bit.

 /// zero bit.
 ///
 /// Ex. countLeadingOnes(0xFF0FFF00) == 8.
 /// Only unsigned integral types are allowed.
 ///
 /// \param ZB the behavior on an input of all ones. Only ZB_Width and
 /// ZB_Undefined are valid arguments.
 template <typename T>
-std::size_t countLeadingOnes(T Value, ZeroBehavior ZB = ZB_Width) {
+unsigned countLeadingOnes(T Value, ZeroBehavior ZB = ZB_Width) {
   static_assert(std::numeric_limits<T>::is_integer &&
                     !std::numeric_limits<T>::is_signed,
                 "Only unsigned integral types are allowed.");
   return countLeadingZeros<T>(~Value, ZB);
 }
 
 /// Count the number of ones from the least significant bit to the first
 /// zero bit.
 ///
 /// Ex. countTrailingOnes(0x00FF00FF) == 8.
 /// Only unsigned integral types are allowed.
 ///
 /// \param ZB the behavior on an input of all ones. Only ZB_Width and
 /// ZB_Undefined are valid arguments.
 template <typename T>
-std::size_t countTrailingOnes(T Value, ZeroBehavior ZB = ZB_Width) {
+unsigned countTrailingOnes(T Value, ZeroBehavior ZB = ZB_Width) {
   static_assert(std::numeric_limits<T>::is_integer &&
                     !std::numeric_limits<T>::is_signed,
                 "Only unsigned integral types are allowed.");
   return countTrailingZeros<T>(~Value, ZB);
 }
 
 namespace detail {
 template <typename T, std::size_t SizeOfT> struct PopulationCounter {