X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=ebd048be8474800eb6507a5dfb64bfacc18061eb;hp=84e576c62d1577a3615e4e11f465ae8bb3d82c45;hb=374c9e6b63d0e233371;hpb=32d3a07c6710e84d78999cb69c6a866b0bfff482

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 84e576c6..ebd048be 100644
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -58,6 +58,7 @@ namespace {
   CACHE_LINE_ALIGNMENT
 
   int BSFTable[64];
+  int MS1BTable[256];
   Bitboard RTable[0x19000]; // Storage space for rook attacks
   Bitboard BTable[0x1480];  // Storage space for bishop attacks
 
@@ -140,6 +141,26 @@ Square pop_1st_bit(Bitboard* b) {
 
 #endif // !defined(USE_BSFQ)
 
+#if !defined(USE_BSFQ)
+
+Square last_1(Bitboard b) {
+  int result = 0;
+  if (b > 0xFFFFFFFF) {
+    b >>= 32;
+    result = 32;
+  }
+  if (b > 0xFFFF) {
+    b >>= 16;
+    result += 16;
+  }
+  if (b > 0xFF) {
+    b >>= 8;
+    result += 8;
+  }
+  return Square(result + MS1BTable[b]);
+}
+
+#endif // !defined(USE_BSFQ)
 
 /// bitboards_init() initializes various bitboard arrays. It is called during
 /// program initialization.
@@ -196,6 +217,11 @@ void bitboards_init() {
       else
           BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i;
 
+  MS1BTable[0] = 0;
+  for (int i = 0, k = 1; i < 8; i++)
+    for (int j = 0; j < (1 << i); j++)
+      MS1BTable[k++] = i;
+
   int steps[][9] = { {}, { 7, 9 }, { 17, 15, 10, 6, -6, -10, -15, -17 },
                      {}, {}, {}, { 9, 7, -7, -9, 8, 1, -1, -8 } };