From: Joost VandeVondele <Joost.VandeVondele@gmail.com>
Date: Sat, 27 Jun 2020 06:23:46 +0000 (+0200)
Subject: Revert LTO for mingw on windows.
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=ca41ee6632368676a2fb98fd2970ac9b183f0aa9

Revert LTO for mingw on windows.

LTO with static linking is still only working with the latest versions of gcc,
causing problems for some devs.

on a modern mingw toolchain LTO optimizations can still be enabled as:

```
CXXFLAGS='-flto' make -j ARCH=x86-64-modern COMP=mingw profile-build
```

fixes https://github.com/official-stockfish/Stockfish/issues/2769

closes https://github.com/official-stockfish/Stockfish/pull/2774

No functional change.
---

diff --git a/src/Makefile b/src/Makefile
index 492403d3..c3660a20 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -344,10 +344,20 @@ endif
 ### needs access to the optimization flags.
 ifeq ($(optimize),yes)
 ifeq ($(debug), no)
-	ifeq ($(comp),$(filter $(comp),gcc clang mingw))
+	ifeq ($(comp),$(filter $(comp),gcc clang))
 		CXXFLAGS += -flto
 		LDFLAGS += $(CXXFLAGS)
 	endif
+
+# To use LTO and static linking on windows, the tool chain requires a recent gcc:
+# gcc version 10.1 in msys2 or TDM-GCC version 9.2 are know to work, older might not.
+# So, only enable it for a cross from Linux by default.
+	ifeq ($(comp),mingw)
+	ifeq ($(KERNEL),Linux)
+		CXXFLAGS += -flto
+		LDFLAGS += $(CXXFLAGS)
+	endif
+	endif
 endif
 endif