X-Git-Url: https://git.libre-soc.org/?a=blobdiff_plain;f=src%2Fbase%2Fbitfield.hh;h=5a98b13c75e219383499e5ce4de467a1fe7389ad;hb=97887eb6dc9e548c9b5719727fd4783ef157917c;hp=28093a5d44e45e8732f885eefcfdd56b0b98b666;hpb=709d859530325f28b904001f5a55dbdec2bad199;p=gem5.git

diff --git a/src/base/bitfield.hh b/src/base/bitfield.hh
index 28093a5d4..5a98b13c7 100644
--- a/src/base/bitfield.hh
+++ b/src/base/bitfield.hh
@@ -92,7 +92,7 @@ mask(int first, int last)
  */
 template <int N>
 inline
-int64_t
+uint64_t
 sext(uint64_t val)
 {
     int sign_bit = bits(val, N-1, N-1);
@@ -161,4 +161,54 @@ findMsbSet(uint64_t val) {
     return msb;
 }
 
+/**
+ * Returns the bit position of the LSB that is set in the input
+ */
+inline int
+findLsbSet(uint64_t val) {
+    int lsb = 0;
+    if (!val)
+        return sizeof(val) * 8;
+    if (!bits(val, 31,0)) { lsb += 32; val >>= 32; }
+    if (!bits(val, 15,0)) { lsb += 16; val >>= 16; }
+    if (!bits(val, 7,0))  { lsb += 8;  val >>= 8;  }
+    if (!bits(val, 3,0))  { lsb += 4;  val >>= 4;  }
+    if (!bits(val, 1,0))  { lsb += 2;  val >>= 2;  }
+    if (!bits(val, 0,0))  { lsb += 1; }
+    return lsb;
+}
+
+/**
+ * Checks if a number is a power of two, or zero.
+ */
+template <class T>
+inline bool
+isPow2(T v) {
+   return (v & (v - 1)) == (T)0;
+}
+
+/**
+ * Returns the number of set ones in the provided value.
+ * PD algorithm from
+ * http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
+ */
+inline int
+popCount(uint64_t val) {
+#ifndef __has_builtin
+    #define __has_builtin(foo) 0
+#endif
+#if defined(__GNUC__) || (defined(__clang__) && __has_builtin(__builtin_popcountl))
+    return __builtin_popcountl(val);
+#else
+    const uint64_t m1 = 0x5555555555555555;  // ..010101b
+    const uint64_t m2 = 0x3333333333333333;  // ..110011b
+    const uint64_t m4 = 0x0f0f0f0f0f0f0f0f;  // ..001111b
+    const uint64_t sum = 0x0101010101010101;
+
+    val -= (val >> 1) & m1;               // 2 bits count -> 2 bits
+    val = (val & m2) + ((val >> 2) & m2); // 4 bits count -> 4 bits
+    val = (val + (val >> 4)) & m4;        // 8 bits count -> 8 bits
+    return (val * sum) >> 56;             // horizontal sum
+#endif // defined(__GNUC__) || (defined(__clang__) && __has_builtin(__builtin_popcountl))
+}
 #endif // __BASE_BITFIELD_HH__