From 550fed3343089357dc89ecf78ce8eb4b35bcab88 Mon Sep 17 00:00:00 2001
From: Gian-Carlo Pascutto <gcp@sjeng.org>
Date: Tue, 9 Feb 2021 17:38:58 +0100
Subject: [PATCH] Enable New Pass Manager for Clang.

It's about 1% speedup for Stockfish.

Result of 100 runs
==================
base (...fish_clang12) =    1946851  +/- 3717
test (./stockfish    ) =    1967276  +/- 3408
diff                   =     +20425  +/- 2438

speedup        = +0.0105
P(speedup > 0) =  1.0000

Thanks to David Major for making me aware of this part
of LLVM development.

closes https://github.com/official-stockfish/Stockfish/pull/3346

No functional change
---
 src/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Makefile b/src/Makefile
index 827ce6bb..1ff03f83 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -481,6 +481,10 @@ ifeq ($(optimize),yes)
 			CXXFLAGS += -mdynamic-no-pic
 		endif
 	endif
+
+	ifeq ($(comp),clang)
+		CXXFLAGS += -fexperimental-new-pass-manager
+	endif
 endif
 
 ### 3.4 Bits
-- 
2.39.2