Use compiler intrinsic instead of assembly for popcnt

This time, do not break compatibility with some AMD machines that have SSE3 and popcnt, but do
not have SSE4.2.

No functional change.

diff --git a/src/Makefile b/src/Makefile
index 187e7b3..1e5a165 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -285,7 +285,7 @@ endif
 
 ### 3.9 popcnt
 ifeq ($(popcnt),yes)
-       CXXFLAGS += -msse3 -DUSE_POPCNT
+       CXXFLAGS += -msse3 -mpopcnt -DUSE_POPCNT
 endif
 
 ### 3.10 pext

diff --git a/src/bitcount.h b/src/bitcount.h
index f84c51c..9feed19 100644 (file)
--- a/src/bitcount.h
+++ b/src/bitcount.h
@@ -96,8 +96,7 @@ inline int popcount<CNT_HW_POPCNT>(Bitboard b) {
 
 #else
 
-  __asm__("popcnt %1, %0" : "=r" (b) : "r" (b));
-  return b;
+  return __builtin_popcountll(b);
 
 #endif
 }