From 6bd9ec37356a38456dd8eef4a882abe6d9ce222b Mon Sep 17 00:00:00 2001
From: Joel Dice <joel.dice@gmail.com>
Date: Sat, 26 Mar 2011 14:44:08 -0600
Subject: [PATCH] enable link time optimization when using GCC 4.6 or greater

---
 makefile | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/makefile b/makefile
index d9921f3e3b..8d83a40982 100644
--- a/makefile
+++ b/makefile
@@ -354,9 +354,22 @@ ifeq ($(mode),stress-major)
 endif
 ifeq ($(mode),fast)
 	optimization-cflags = -O3 -g3 -DNDEBUG
+	use-lto = true
 endif
 ifeq ($(mode),small)
 	optimization-cflags = -Os -g3 -DNDEBUG
+	use-lto = true
+endif
+
+ifeq ($(use-lto),true)
+# only try to use LTO when GCC 4.6.0 or greater is available
+	gcc-major := $(shell $(cc) -dumpversion | cut -f1 -d.)
+	gcc-minor := $(shell $(cc) -dumpversion | cut -f2 -d.)
+	ifeq ($(shell expr 4 \< $(gcc-major) \
+			\| \( 4 \<= $(gcc-major) \& 6 \<= $(gcc-minor) \)),1)
+		optimization-cflags += -flto
+		lflags += $(optimization-cflags)
+	endif
 endif
 
 cflags += $(optimization-cflags)