From 08f3aac97c9ee9d9a4cf0a3232ac0bfa4c320896 Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Fri, 3 Jul 2009 13:18:59 +0100
Subject: [PATCH] Do not compile POPCNT if NO_POPCNT is defined

Also rename DISABLE_POPCNT_SUPPORT in NO_POPCNT and simplify a bit
the macro logic.

Always define a __popcnt64()or _mm_popcnt_u64() template, if the proper
function with the same name is defined in the intrinsics header, then it
will be choosen as first otherwise we fall back on the dummy template
that is never called at runtime anyway because cpu_has_popcnt() returns
false.

This fixes the compile error reported by Jim.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---
 src/bitcount.h | 36 ++++++++++++++++++++++++------------
 src/types.h    |  2 +-
 2 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/src/bitcount.h b/src/bitcount.h
index 4747afc6..9a3b4811 100644
--- a/src/bitcount.h
+++ b/src/bitcount.h
@@ -22,17 +22,18 @@
 #if !defined(BITCOUNT_H_INCLUDED)
 #define BITCOUNT_H_INCLUDED
 
-// To disable POPCNT support uncomment following line. You should do it only
+// To disable POPCNT support uncomment NO_POPCNT define. 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
+
+//#define NO_POPCNT
 
 
 #include "types.h"
 
 // Select type of intrinsic bit count instruction to use
 
-#if defined(_MSC_VER) && defined(_WIN64) // Microsoft compiler
+#if defined(_MSC_VER) && defined(IS_64BIT) && !defined(NO_POPCNT) // Microsoft compiler
 
 #include <intrin.h>
 
@@ -43,9 +44,17 @@ inline bool cpu_has_popcnt() {
   return (CPUInfo[2] >> 23) & 1;
 }
 
+// Define a dummy template to workaround a compile error if __popcnt64() is not defined.
+//
+// If __popcnt64() is defined in <intrin.h> it will be choosen first due to
+// C++ overload rules that always prefer a function to a template with the same name.
+// If not, we avoid a compile error and because cpu_has_popcnt() should return false,
+// our templetized __popcnt64() is never called anyway.
+template<typename T> unsigned __popcnt64(T) { return 0; } // Is never called
+
 #define POPCNT_INTRINSIC(x) __popcnt64(x)
 
-#elif defined(__INTEL_COMPILER) && (defined(__x86_64) || defined(_M_X64)) // Intel compiler
+#elif defined(__INTEL_COMPILER) && defined(IS_64BIT) && !defined(NO_POPCNT) // Intel compiler
 
 #include <nmmintrin.h>
 
@@ -56,15 +65,18 @@ inline bool cpu_has_popcnt() {
   return (CPUInfo[2] >> 23) & 1;
 }
 
+// See comment of __popcnt64<>() few lines above for an explanation.
+template<typename T> unsigned _mm_popcnt_u64(T) { return 0; } // Is never called
+
 #define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
 
-#else // Safe fallback for unsupported compilers
+#else // Safe fallback for unsupported compilers or when NO_POPCNT is defined
 
 inline bool cpu_has_popcnt() { return false; }
 
-#define POPCNT_INTRINSIC(x) count_1s(x)
+#define POPCNT_INTRINSIC(x) 0
 
-#endif // cpu_has_popcnt() selection
+#endif // cpu_has_popcnt() and POPCNT_INTRINSIC() definitions
 
 
 /// Software implementation of bit count functions
@@ -131,18 +143,18 @@ inline int count_1s_max_15(Bitboard b) {
 }
 
 
-// Global variable initialized at startup that is set to true if
+// Global constant 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)
+// NO_POPCNT is defined.
+#if defined(NO_POPCNT)
 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.
+// Global constant used to print info about the use of 64 optimized
+// functions to verify that a 64 bit compile has been correctly built.
 #if defined(IS_64BIT)
 const bool CpuHas64BitPath = true;
 #else
diff --git a/src/types.h b/src/types.h
index 577f97d7..af5e2455 100644
--- a/src/types.h
+++ b/src/types.h
@@ -58,7 +58,7 @@ typedef uint64_t Bitboard;
 #endif
 
 // Check for 64 bits for different compilers: Intel, MSVC and gcc
-#if defined(__x86_64) || defined(_WIN64) || (__SIZEOF_INT__ > 4)
+#if defined(__x86_64) || defined(_M_X64) || defined(_WIN64) || (__SIZEOF_INT__ > 4)
 #define IS_64BIT
 #endif
 
-- 
2.39.2