Add bit_ceil method .patch to trunk

Add bit_ceil method .patch to trunk

Author: bokrzesi

external/llvm/trunk/patches_external/llvm_bit_ceil.patch

@@ -0,0 +1,66 @@
+From eaabc1bbeaa057bac3fe699bebda1472dc2ae03b Mon Sep 17 00:00:00 2001
+From: Kazu Hirata <[email protected]>
+Date: Fri, 20 Jan 2023 19:34:42 -0800
+Subject: [PATCH] [ADT] Add bit_floor, bit_ceil, and bit_width to bit.h
+
+This patch adds C++20-style bit_floor, bit_ceil, and bit_width.
+
+In a subsequent patch, I'm going to define PowerOf2Floor in
+MathExtras.h in terms of bit_floor.
+
+Unfortunately, PowerOf2Ceil isn't quite the same as bit_ceil because
+PowerOf2Ceil(0) == 0, whereas bit_ceil(0) == 1.
+
+MathExtras.h does not have a function directly corresponding to
+bit_width, but Log2_32(X) + 1, which occurs in a few places, can be
+replaced with bit_width(X).
+
+Differential Revision: https://reviews.llvm.org/D142179
+
+diff --git a/llvm/include/llvm/ADT/bit.h b/llvm/include/llvm/ADT/bit.h
+index 442f3795841a..04105bf942c4 100644
+--- a/llvm/include/llvm/ADT/bit.h
++++ b/llvm/include/llvm/ADT/bit.h
+@@ -79,6 +79,42 @@ inline int popcount(T Value) noexcept {
+   return detail::PopulationCounter<T, sizeof(T)>::count(Value);
+ }
+ 
++/// Returns the number of bits needed to represent Value if Value is nonzero.
++ /// Returns 0 otherwise.
++ ///
++ /// Ex. bit_width(5) == 3.
++ template <typename T> int bit_width(T Value) {
++  static_assert(std::is_unsigned_v<T>,
++                "Only unsigned integral types are allowed.");
++  return std::numeric_limits<T>::digits - llvm::countl_zero(Value);
++}
++
++/// Returns the largest integral power of two no greater than Value if Value is
++/// nonzero.  Returns 0 otherwise.
++///
++/// Ex. bit_floor(5) == 4.
++template <typename T> T bit_floor(T Value) {
++  static_assert(std::is_unsigned_v<T>,
++                "Only unsigned integral types are allowed.");
++  if (!Value)
++    return 0;
++  return T(1) << (llvm::bit_width(Value) - 1);
++}
++
++/// Returns the smallest integral power of two no smaller than Value if Value is
++/// nonzero.  Returns 0 otherwise.
++///
++/// Ex. bit_ceil(5) == 8.
++///
++/// The return value is undefined if the input is larger than the largest power
++/// of two representable in T.
++template <typename T> T bit_ceil(T Value) {
++  static_assert(std::is_unsigned_v<T>,
++                "Only unsigned integral types are allowed.");
++  if (Value < 2)
++    return 1;
++  return T(1) << llvm::bit_width<T>(Value - 1u);
++}
+ } // namespace llvm
+ 
+ #endif