enable bit manipulation instruction set 1

bmi1 enables the use of _blsr_u64 for pop_lsb, and is availabe when avx2 is.

verified a small speedup (0.2 - 0.6%)

closes https://github.com/official-stockfish/Stockfish/pull/4202

No functional change

diff --git a/src/Makefile b/src/Makefile
index 1d5137d1c507c164315cfc0100bf6f3dd7fb2fbf..727466f9b57f3565d81b8bbde1c98118d0c62e4e 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -593,7 +593,7 @@ endif
 ifeq ($(avx2),yes)
        CXXFLAGS += -DUSE_AVX2
        ifeq ($(comp),$(filter $(comp),gcc clang mingw))
-               CXXFLAGS += -mavx2
+               CXXFLAGS += -mavx2 -mbmi
        endif
 endif