From 360872d269e799c9c8237c06e8271f0c27eb9910 Mon Sep 17 00:00:00 2001
From: tmk <hasu@tmk-kbd.com>
Date: Tue, 31 May 2022 13:16:30 +0900
Subject: [PATCH] core: Build option for LTO(Link Time Optimization)

This makes firmware size small but need to be tested more.
https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Optimize-Options
https://github.com/arduino/Arduino/issues/660
https://github.com/arduino/ArduinoCore-avr/blob/master/platform.txt

* No `-fno-fat-lto-objects` is needed, it is the default.
https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-ffat-lto-objects
* No `-fuse-linker-plugin` is needed, it is the default.
https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-fuse-linker-plugin
---
 tmk_core/rules.mk | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tmk_core/rules.mk b/tmk_core/rules.mk
index b559e57b..cd2c0d8b 100644
--- a/tmk_core/rules.mk
+++ b/tmk_core/rules.mk
@@ -139,6 +139,7 @@ CFLAGS += -Wstrict-prototypes
 CFLAGS += -Wa,-adhlns=$(@:%.o=%.lst)
 CFLAGS += $(patsubst %,-I%,$(EXTRAINCDIRS))
 CFLAGS += $(CSTANDARD)
+CFLAGS += -flto
 ifdef CONFIG_H
     CFLAGS += -include $(CONFIG_H)
 endif
@@ -173,6 +174,7 @@ CPPFLAGS += -Wundef
 CPPFLAGS += -Wa,-adhlns=$(@:%.o=%.lst)
 CPPFLAGS += $(patsubst %,-I%,$(EXTRAINCDIRS))
 #CPPFLAGS += $(CSTANDARD)
+CPPFLAGS += -flto
 ifdef CONFIG_H
     CPPFLAGS += -include $(CONFIG_H)
 endif
@@ -189,6 +191,7 @@ endif
 #       dump that will be displayed for a given single line of source input.
 ASFLAGS = $(ADEFS) -Wa,-adhlns=$(@:%.o=%.lst),-gstabs,--listing-cont-lines=100
 ASFLAGS += $(patsubst %,-I%,$(EXTRAINCDIRS))
+ASFLAGS += -flto
 ifdef CONFIG_H
     ASFLAGS += -include $(CONFIG_H)
 endif
@@ -261,6 +264,7 @@ LDFLAGS += $(PRINTF_LIB) $(SCANF_LIB) $(MATH_LIB)
 #LDFLAGS += -T linker_script.x
 # You can give EXTRALDFLAGS at 'make' command line.
 LDFLAGS += $(EXTRALDFLAGS)
+LDFLAGS += -flto