From 0cd9e7a935a14f4404ba2b8b458ab11c8443c4ad Mon Sep 17 00:00:00 2001
From: Michael Tremer <michael.tremer@ipfire.org>
Date: Fri, 26 Feb 2021 11:26:57 +0000
Subject: [PATCH] make.sh: Add -flto to CFLAGS

This will compile the whole distribition with LTO.

GCC will generate some intermediate representation of the code which
will be compiled into binary at linking stage, after an optimizer
has removed any unneeded symbols and the inliner has had a chance to
inline functions across source files.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---
 lfs/Config |  3 +++
 make.sh    | 30 +++++++++++++++++-------------
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/lfs/Config b/lfs/Config
index 7d98e303b4..00d8eedb1c 100644
--- a/lfs/Config
+++ b/lfs/Config
@@ -44,6 +44,9 @@ PARALLELISM = $(shell echo $$( \
 	fi) \
 )
 
+# Enable LTO
+CFLAGS += $(CFLAGS_LTO)
+
 MAKETUNING = -j$(PARALLELISM)
 
 ifeq "$(BUILD_ARCH)" "aarch64"
diff --git a/make.sh b/make.sh
index 78b93c4098..98cfc591d2 100755
--- a/make.sh
+++ b/make.sh
@@ -144,6 +144,20 @@ system_memory() {
 configure_build() {
 	local build_arch="${1}"
 
+	# Determine parallelism
+	# We assume that each process consumes about
+	# 128MB of memory. Therefore we find out how
+	# many processes fit into memory.
+	local mem_max=$(( ${SYSTEM_MEMORY} / 128 ))
+	local cpu_max=$(( ${SYSTEM_PROCESSORS} ))
+
+	local parallelism
+	if [ ${mem_max} -lt ${cpu_max} ]; then
+		parallelism=${mem_max}
+	else
+		parallelism=${cpu_max}
+	fi
+
 	if [ "${build_arch}" = "default" ]; then
 		build_arch="$(configure_build_guess)"
 	fi
@@ -217,19 +231,8 @@ configure_build() {
 	CFLAGS="-O2 -pipe -Wall -fexceptions -fPIC ${CFLAGS_ARCH}"
 	CXXFLAGS="${CFLAGS}"
 
-	# Determine parallelism
-	# We assume that each process consumes about
-	# 128MB of memory. Therefore we find out how
-	# many processes fit into memory.
-	local mem_max=$(( ${SYSTEM_MEMORY} / 128 ))
-	local cpu_max=$(( ${SYSTEM_PROCESSORS} ))
-
-	local parallelism
-	if [ ${mem_max} -lt ${cpu_max} ]; then
-		parallelism=${mem_max}
-	else
-		parallelism=${cpu_max}
-	fi
+	# Enable LTO
+	CFLAGS_LTO="-flto=${parallelism} -ffat-lto-objects"
 
 	# Use this as default PARALLELISM
 	DEFAULT_PARALLELISM="${parallelism}"
@@ -586,6 +589,7 @@ enterchroot() {
 		CONFIG_ROOT="${CONFIG_ROOT}" \
 		CFLAGS="${CFLAGS} ${HARDENING_CFLAGS}" \
 		CXXFLAGS="${CXXFLAGS} ${HARDENING_CFLAGS}" \
+		CFLAGS_LTO="${CFLAGS_LTO}" \
 		RUSTFLAGS="${RUSTFLAGS}" \
 		BUILDTARGET="${BUILDTARGET}" \
 		CROSSTARGET="${CROSSTARGET}" \
-- 
2.39.5