X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=298db7a7ee357764540bd61990df8f84929e63a6;hp=5dd0137da39d225d34b4a41bb48279851fa29644;hb=1d8994402bc6d3132f5147194a8b54e1c00b27a6;hpb=9ae2b6923504064da184d08b888fffb328818543

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 5dd0137d..298db7a7 100644
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -21,6 +21,16 @@
 //// Includes
 ////
 
+#ifdef _MSC_VER
+    #include <intrin.h>
+    #ifdef _WIN64
+        #pragma intrinsic(_BitScanForward64)
+    #else
+        #pragma intrinsic(_BitScanForward)
+    #endif
+    #define USING_INTRINSICS
+#endif
+
 #include <iostream>
 
 #include "bitboard.h"
@@ -339,22 +349,30 @@ Square first_1(Bitboard b) {
 /// pop_1st_bit() finds and clears the least significant nonzero bit in a
 /// nonzero bitboard.
 
-#if defined(USE_32BIT_ATTACKS)
-
-Square pop_1st_bit(Bitboard *bb) {
-
-  uint32_t  t = uint32_t(*bb);
-  uint32_t* p = t ? (uint32_t*)bb : (uint32_t*)bb + 1; // Little endian only?
-  uint32_t  b = t ? t : *p;
+#if defined(USE_32BIT_ATTACKS) && defined(_MSC_VER)
 
-  *p = b & (b -1);
+// On 32bit system compiled with MSVC this verion seems
+// slightly faster then the standard one.
 
-  if (t)
-     b ^= (b - 1);
-  else
-     b = ~(b ^ (b - 1));
+Square pop_1st_bit(Bitboard *b) {
 
-  return Square(BitTable[(b * 0x783a9b23) >> 26]);
+    unsigned long index;
+    uint32_t *l, *h;
+
+    if (*(l = (uint32_t*)b) != 0)
+    {
+        _BitScanForward(&index, *l);
+        *l &= ~(1 << index);
+    } 
+    else if (*(h = (uint32_t*)b + 1) != 0)
+    {
+        _BitScanForward(&index, *h);
+        *h &= ~(1 << index);
+        index += 32;
+    } else
+        return SQ_NONE;
+
+    return Square(index);
 }
 
 #else