From: Niklas Fiekas <niklas.fiekas@backscattering.de>
Date: Thu, 25 Jun 2020 10:42:25 +0000 (+0200)
Subject: support popcnt on armv8
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=aecfca2dc2d760df257e18cd6b29d266a3c3e68a

support popcnt on armv8

* Supports popcnt (thanks @daylen)
* bits = 64 is now the default

Tested with g++ (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04) 7.5.0 on ThunderX CN8890,
yields about 9% speedup.

Also tested with clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final).

closes https://github.com/official-stockfish/Stockfish/pull/2770

No functional change.
---

diff --git a/src/Makefile b/src/Makefile
index 81731e66..492403d3 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -134,8 +134,8 @@ endif
 
 ifeq ($(ARCH),armv8)
 	arch = armv8-a
-	bits = 64
 	prefetch = yes
+	popcnt = yes
 endif
 
 ifeq ($(ARCH),ppc-32)
@@ -322,7 +322,7 @@ endif
 
 ### 3.6 popcnt
 ifeq ($(popcnt),yes)
-	ifeq ($(arch),ppc64)
+	ifeq ($(arch),$(filter $(arch),ppc64 armv8-a))
 		CXXFLAGS += -DUSE_POPCNT
 	else ifeq ($(comp),icc)
 		CXXFLAGS += -msse3 -DUSE_POPCNT