Vendor import of llvm trunk r300890:vendor/llvm/llvm-trunk-r300890

https://llvm.org/svn/llvm-project/llvm/trunk@300890

1 files changed, 16 insertions, 0 deletions

diff --git a/include/llvm/Support/MathExtras.h b/include/llvm/Support/MathExtras.h
index 19380b23d9d2..994456f9a681 100644
--- a/include/llvm/Support/MathExtras.h
+++ b/include/llvm/Support/MathExtras.h
@@ -18,6 +18,7 @@
 #include "llvm/Support/SwapByteOrder.h"
 #include <algorithm>
 #include <cassert>
+#include <climits>
 #include <cstring>
 #include <type_traits>
 #include <limits>
@@ -198,6 +199,21 @@ template <typename T> T findFirstSet(T Val, ZeroBehavior ZB = ZB_Max) {
   return countTrailingZeros(Val, ZB_Undefined);
 }
 
+/// \brief Create a bitmask with the N right-most bits set to 1, and all other
+/// bits set to 0.  Only unsigned types are allowed.
+template <typename T> T maskTrailingOnes(unsigned N) {
+  static_assert(std::is_unsigned<T>::value, "Invalid type!");
+  const unsigned Bits = CHAR_BIT * sizeof(T);
+  assert(N <= Bits && "Invalid bit index");
+  return N == 0 ? 0 : (T(-1) >> (Bits - N));
+}
+
+/// \brief Create a bitmask with the N left-most bits set to 1, and all other
+/// bits set to 0.  Only unsigned types are allowed.
+template <typename T> T maskLeadingOnes(unsigned N) {
+  return ~maskTrailingOnes<T>(CHAR_BIT * sizeof(T) - N);
+}
+
 /// \brief Get the index of the last set bit starting from the least
 ///   significant bit.
 ///