From 4d8c75077eac34b4fc48510298cd1f7d215dddc5 Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Fri, 13 Feb 2015 16:13:15 +0100
Subject: [PATCH] Configure: Experimental CONFIG_LTO

---
 default.cfg                 |  3 +++
 ucw/perl/UCW/Configure/C.pm | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/default.cfg b/default.cfg
index 9a43ab60..4788b156 100644
--- a/default.cfg
+++ b/default.cfg
@@ -10,6 +10,9 @@ Set("CONFIG_DEBUG");
 # We want the public API
 Set("CONFIG_INSTALL_API");
 
+# Enable GCC link-time optimizations (experimental)
+UnSet("CONFIG_LTO");
+
 # LibUCW should support files >2GB and threading
 Set("CONFIG_UCW_LARGE_FILES");
 Set("CONFIG_UCW_THREADS" => 1);
diff --git a/ucw/perl/UCW/Configure/C.pm b/ucw/perl/UCW/Configure/C.pm
index 95644b45..7cd3da9e 100644
--- a/ucw/perl/UCW/Configure/C.pm
+++ b/ucw/perl/UCW/Configure/C.pm
@@ -170,6 +170,16 @@ if (IsSet("CONFIG_DEBUG")) {
 	Append("LOPT" => "-s");
 }
 
+# Link-time optimization (experimental)
+# This is currently very inefficient, because we do not attempt to disable
+# optimizations when compiling individual modules. Therefore, we optimize
+# each shared library module twice: when compiling and when linking.
+# Doing it properly would require hacking makefiles.
+if (IsSet("CONFIG_LTO")) {
+	Append("LOPT", "-flto");
+	Append("COPT", "-flto");
+}
+
 if (IsSet("CONFIG_DARWIN")) {
 	# gcc-4.0 on Darwin doesn't set this in the gnu99 mode
 	Append("CLANG" => "-fnested-functions");
-- 
2.39.2