Fix a warning with __popcnt64() intrinsics

[stockfish] / src / bitcount.h

diff --git a/src/bitcount.h b/src/bitcount.h
index 4747afc6aa73861e7a34785833352fc905c030e4..940dbaf52af207c8a24977e8780b42679e36650c 100644 (file)
--- a/src/bitcount.h
+++ b/src/bitcount.h
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2009 Marco Costalba
+  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -22,56 +22,25 @@
 #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 "types.h"
 
-// Select type of intrinsic bit count instruction to use
-
-#if defined(_MSC_VER) && defined(_WIN64) // Microsoft compiler
-
-#include <intrin.h>
-
-inline bool cpu_has_popcnt() {
-
-  int CPUInfo[4] = {-1};
-  __cpuid(CPUInfo, 0x00000001);
-  return (CPUInfo[2] >> 23) & 1;
-}
-
-#define POPCNT_INTRINSIC(x) __popcnt64(x)
-
-#elif defined(__INTEL_COMPILER) && (defined(__x86_64) || defined(_M_X64)) // Intel compiler
-
-#include <nmmintrin.h>
-
-inline bool cpu_has_popcnt() {
-
-  int CPUInfo[4] = {-1};
-  __cpuid(CPUInfo, 0x00000001);
-  return (CPUInfo[2] >> 23) & 1;
-}
-
-#define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
-
-#else // Safe fallback for unsupported compilers
-
-inline bool cpu_has_popcnt() { return false; }
+enum BitCountType {
+    CNT64,
+    CNT64_MAX15,
+    CNT32,
+    CNT32_MAX15,
+    CNT_POPCNT
+};
 
-#define POPCNT_INTRINSIC(x) count_1s(x)
-
-#endif // cpu_has_popcnt() selection
-
-
-/// Software implementation of bit count functions
-
-#if defined(IS_64BIT)
-
-inline int count_1s(Bitboard b) {
+/// count_1s() counts the number of nonzero bits in a bitboard.
+/// We have different optimized versions according if platform
+/// is 32 or 64 bits, and to the maximum number of nonzero bits.
+/// We also support hardware popcnt instruction. See Readme.txt
+/// on how to pgo compile with popcnt support.
+template<BitCountType> inline int count_1s(Bitboard);
+
+template<>
+inline int count_1s<CNT64>(Bitboard b) {
   b -= ((b>>1) & 0x5555555555555555ULL);
   b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
   b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
@@ -79,16 +48,16 @@ inline int count_1s(Bitboard b) {
   return int(b >> 56);
 }
 
-inline int count_1s_max_15(Bitboard b) {
+template<>
+inline int count_1s<CNT64_MAX15>(Bitboard b) {
   b -= (b>>1) & 0x5555555555555555ULL;
   b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
   b *= 0x1111111111111111ULL;
   return int(b >> 60);
 }
 
-#else // if !defined(IS_64BIT)
-
-inline int count_1s(Bitboard b) {
+template<>
+inline int count_1s<CNT32>(Bitboard b) {
   unsigned w = unsigned(b >> 32), v = unsigned(b);
   v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
   w -= (w >> 1) & 0x55555555;
@@ -100,7 +69,8 @@ inline int count_1s(Bitboard b) {
   return int(v >> 24);
 }
 
-inline int count_1s_max_15(Bitboard b) {
+template<>
+inline int count_1s<CNT32_MAX15>(Bitboard b) {
   unsigned w = unsigned(b >> 32), v = unsigned(b);
   v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
   w -= (w >> 1) & 0x55555555;
@@ -111,42 +81,47 @@ inline int count_1s_max_15(Bitboard b) {
   return int(v >> 28);
 }
 
-#endif // BITCOUNT
-
-
-/// count_1s() counts the number of nonzero bits in a bitboard.
-/// If template parameter is true an intrinsic is called, otherwise
-/// we fallback on a software implementation.
-
-template<bool UseIntrinsic>
-inline int count_1s(Bitboard b) {
-
-  return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s(b);
+template<>
+inline int count_1s<CNT_POPCNT>(Bitboard b) {
+#if !defined(USE_POPCNT)
+  return int(b != 0); // Avoid 'b not used' warning
+#elif defined(_MSC_VER) && defined(__INTEL_COMPILER)
+  return _mm_popcnt_u64(b);
+#elif defined(_MSC_VER)
+  return (int)__popcnt64(b);
+#elif defined(__GNUC__)
+  unsigned long ret;
+  __asm__("popcnt %1, %0" : "=r" (ret) : "r" (b));
+  return ret;
+#endif
 }
 
-template<bool UseIntrinsic>
-inline int count_1s_max_15(Bitboard b) {
 
-  return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s_max_15(b);
+/// cpu_has_popcnt() detects support for popcnt instruction at runtime
+inline bool cpu_has_popcnt() {
+
+  int CPUInfo[4] = {-1};
+  __cpuid(CPUInfo, 0x00000001);
+  return (CPUInfo[2] >> 23) & 1;
 }
 
 
-// Global variable initialized at startup that is set to true if
-// CPU on which application runs supports POPCNT intrinsic. Unless
-// DISABLE_POPCNT_SUPPORT is defined.
-#if defined(DISABLE_POPCNT_SUPPORT)
-const bool CpuHasPOPCNT = false;
-#else
+/// CpuHasPOPCNT is a global constant initialized at startup that
+/// is set to true if CPU on which application runs supports popcnt
+/// hardware instruction. Unless USE_POPCNT is not defined.
+#if defined(USE_POPCNT)
 const bool CpuHasPOPCNT = cpu_has_popcnt();
+#else
+const bool CpuHasPOPCNT = false;
 #endif
 
 
-// Global variable used to print info about the use of 64 optimized
-// functions to verify that a 64bit compile has been correctly built.
+/// CpuIs64Bit is a global constant initialized at compile time that
+/// is set to true if CPU on which application runs is a 64 bits.
 #if defined(IS_64BIT)
-const bool CpuHas64BitPath = true;
+const bool CpuIs64Bit = true;
 #else
-const bool CpuHas64BitPath = false;
+const bool CpuIs64Bit = false;
 #endif
 
 #endif // !defined(BITCOUNT_H_INCLUDED)