Enable _BitScanForward64 in move generation

[stockfish] / src / bitcount.h

diff --git a/src/bitcount.h b/src/bitcount.h
index a4133fb21723db8981205fdf6f0f843f580e0190..41a1446e01b700b7d6fa08b9425b1a199a2a9122 100644 (file)
--- a/src/bitcount.h
+++ b/src/bitcount.h
@@ -22,6 +22,12 @@
 #if !defined(BITCOUNT_H_INCLUDED)
 #define BITCOUNT_H_INCLUDED
 
+// To disable POPCNT support uncomment following line. You should do it only
+// in PGO compiling to exercise the default fallback path. Don't forget to
+// re-comment the line for the final optimized compile though ;-)
+//#define DISABLE_POPCNT_SUPPORT
+
+
 #include "bitboard.h"
 
 
@@ -60,6 +66,7 @@ inline bool cpu_has_popcnt() {
 }
 
 #define POPCNT_INTRINSIC(x) __popcnt64(x)
+#define BITSCAN_INTRINSIC(idx, x) _BitScanForward64(idx, x)
 
 #elif defined(__INTEL_COMPILER) && (defined(__x86_64) || defined(_M_X64)) // Intel compiler
 
@@ -73,12 +80,14 @@ inline bool cpu_has_popcnt() {
 }
 
 #define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
+#define BITSCAN_INTRINSIC(idx, x) _BitScanForward64(idx, x)
 
 #else // Safe fallback for unsupported compilers
 
 inline bool cpu_has_popcnt() { return false; }
 
 #define POPCNT_INTRINSIC(x) sw_count_1s(x)
+#define BITSCAN_INTRINSIC(idx, x) sw_count_1s(x) // dummy
 
 #endif
 
@@ -160,8 +169,42 @@ inline int count_1s_max_15(Bitboard b) {
 
 
 // Global variable initialized at startup that is set to true if
-// CPU on which application runs support POPCNT intrinsic.
-
+// CPU on which application runs supports POPCNT intrinsic. Unless
+// DISABLE_POPCNT_SUPPORT is defined.
+#if defined(DISABLE_POPCNT_SUPPORT)
+const bool CpuHasPOPCNT = false;
+#else
 const bool CpuHasPOPCNT = cpu_has_popcnt();
+#endif
+
+
+// Global variable used to print info about the use of 64 optimized
+// functions to verify that a 64bit compile has been correctly built.
+#if defined(BITCOUNT_SWAR_64)
+const bool CpuHas64BitPath = true;
+#else
+const bool CpuHas64BitPath = false;
+#endif
+
+
+/// pop_1st_bit() finds and clears the least significant nonzero bit in a
+/// nonzero bitboard. If template parameter is true an intrinsic is called,
+/// otherwise we fallback on a software implementation.
+
+template<bool UseIntrinsic>
+inline Square pop_1st_bit(Bitboard *b) {
+
+  return pop_1st_bit(b);
+}
+
+template<>
+inline Square pop_1st_bit<true>(Bitboard *b) {
+
+  unsigned long idx;
+  Bitboard bb = *b;
+  BITSCAN_INTRINSIC(&idx, bb);
+  *b &= (bb - 1);
+  return Square(idx);
+}
 
 #endif // !defined(BITCOUNT_H_INCLUDED)