Add support for LTO

MCUdude · Oct 6, 2016 · 0d5a359 · 0d5a359
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diff --git a/README.md b/README.md
@@ -7,6 +7,7 @@ If you're into "pure" AVR programming, I'm happy to tell you that all relevant k
 * [Supported microcontrollers](#supported-microcontrollers)
 * [Supported clock frequencies](#supported-clock-frequencies)
 * [BOD option](#bod-option)
+* [Link time optimization / LTO](#link-time-optimization--lto)
 * [Programmers](#programmers)
 * [Why add Arduino support for these microcontrollers?](#why-add-arduino-support-for-these-microcontrollers)
 * [Write to own flash](#write-to-own-flash)
@@ -57,6 +58,11 @@ Make sure you connect an ISP programmer, and select the correct one in the "Prog
 Brown out detection, or BOD for short lets the microcontroller sense the input voltage and shut down if the voltage goes below the brown out setting. The ATmega8, ATmega48, ATmega88 and ATmega168 haven't dedicated the BOD selection to extended fuse, so there's no way to only change the BOD option in the Arduino IDE. If you need to change this setting you'll have to edit the boards.txt file.
 
 
+##Link time optimization / LTO
+After Arduino IDE 1.6.11 where released, There have been support for link time optimization or LTO for short. The LTO optimizes the code at link time, making the code (often) significantly smaller without making it "slower". In Arduino IDE 1.6.11 and newer LTO is enabled by default. I've chosen to disable this by default to make sure the core keep its backwards compatibility. Enabling LTO in IDE 1.6.10 and older will return an error. 
+I encourage you to try the new LTO option and see how much smaller your code gets! Note that you don't need to hit "Burn Bootloader" in order to enable LTO. Simply enable it in the "Tools" menu, and your code is ready for compilation. If you want to read more about LTO and GCC flags in general, head over to the [GNU GCC website](https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html)!
+
+
 ##Programmers
 Mini does not adds its own copies of all the standard programmers to the "Programmer" menu. Just select one of the stock programmers in the "Programmers" menu, and you're ready to "Burn Bootloader" or "Upload Using Programmer".
 

diff --git a/avr/boards.txt b/avr/boards.txt
@@ -1,13 +1,24 @@
-# MiniCore - An Arduino core for the ATmega48/P, ATmega8, ATmega88/P, ATmega168/P, ATmega328/P
-# https://github.com/MCUdude/MiniCore
-# Run ./makeall to build all bootloaders
-
+##########################################
+## This file is created by MCUdude 
+## for use with MiniCore
+## https://github.com/MCUdude/MiniCore	
+##
+## This is the file where fuse settings,
+## clock frequencies and compiler flags
+## are located.
+##
+## Run ./makeall to build all bootloaders
+##########################################
+
+# Menu options
 menu.variant=Variant
 menu.clock=Clock
-menu.BOD=B.O.D
-
+menu.BOD=BOD 
+menu.LTO=Compiler LTO
 
-############################################################
+##########################
+#### ATmega328/A/P/PA ####
+##########################
 
 328.name=ATmega328
 328.upload.tool=avrdude
@@ -23,11 +34,13 @@ menu.BOD=B.O.D
 328.build.board=AVR_ATmega328
 328.build.variant=standard
 
+# Variants
 328.menu.variant.modelP=328P / 328PA
 328.menu.variant.modelP.build.mcu=atmega328p
 328.menu.variant.modelNonP=328 / 328A
 328.menu.variant.modelNonP.build.mcu=atmega328
 
+# Brown out detection
 328.menu.BOD.2v7=2.7v
 328.menu.BOD.2v7.bootloader.extended_fuses=0xfd
 328.menu.BOD.4v3=4.3v
@@ -37,7 +50,20 @@ menu.BOD=B.O.D
 328.menu.BOD.disabled=Disabled
 328.menu.BOD.disabled.bootloader.extended_fuses=0xff
 
+# Compiler link time optimization
+328.menu.LTO.Os=Disabled (default)
+328.menu.LTO.Os.compiler.c.extra_flags=
+328.menu.LTO.Os.compiler.c.elf.extra_flags=
+328.menu.LTO.Os.compiler.cpp.extra_flags=
+328.menu.LTO.Os.ltoarcmd=avr-ar
+
+328.menu.LTO.Os_flto=Enabled
+328.menu.LTO.Os_flto.compiler.c.extra_flags=-Wextra -flto
+328.menu.LTO.Os_flto.compiler.c.elf.extra_flags=-w -flto
+328.menu.LTO.Os_flto.compiler.cpp.extra_flags=-Wextra -flto
+328.menu.LTO.Os_flto.ltoarcmd=avr-gcc-ar
 
+# Clock frequencies
 #make atmega328p AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 #make atmega328 AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 328.menu.clock.16MHz_external=16 MHz external
@@ -97,7 +123,9 @@ menu.BOD=B.O.D
 328.menu.clock.1MHz_internal.build.f_cpu=1000000L
 
 
-############################################################
+##########################
+#### ATmega168/A/P/PA ####
+##########################
 
 168.name=ATmega168
 168.upload.tool=avrdude
@@ -113,12 +141,26 @@ menu.BOD=B.O.D
 168.build.board=AVR_ATmega168
 168.build.variant=standard
 
+# Variants
 168.menu.variant.modelP=168P / 168PA
 168.menu.variant.modelP.build.mcu=atmega168p
 168.menu.variant.modelNonP=168 / 168A
 168.menu.variant.modelNonP.build.mcu=atmega168
 
+# Compiler link time optimization
+168.menu.LTO.Os=Disabled (default)
+168.menu.LTO.Os.compiler.c.extra_flags=
+168.menu.LTO.Os.compiler.c.elf.extra_flags=
+168.menu.LTO.Os.compiler.cpp.extra_flags=
+168.menu.LTO.Os.ltoarcmd=avr-ar
 
+168.menu.LTO.Os_flto=Enabled
+168.menu.LTO.Os_flto.compiler.c.extra_flags=-Wextra -flto
+168.menu.LTO.Os_flto.compiler.c.elf.extra_flags=-w -flto
+168.menu.LTO.Os_flto.compiler.cpp.extra_flags=-Wextra -flto
+168.menu.LTO.Os_flto.ltoarcmd=avr-gcc-ar
+
+# Clock frequencies
 #make atmega168p AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 #make atmega168 AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 168.menu.clock.16MHz_external=16 MHz external (BOD 2.7v)
@@ -184,7 +226,9 @@ menu.BOD=B.O.D
 168.menu.clock.1MHz_internal.build.f_cpu=1000000L
 
 
-############################################################
+#########################
+#### ATmega88/A/P/PA ####
+#########################
 
 88.name=ATmega88
 88.upload.tool=avrdude
@@ -200,12 +244,26 @@ menu.BOD=B.O.D
 88.build.board=AVR_ATmega88
 88.build.variant=standard
 
+# Variants
 88.menu.variant.modelP=88P / 88PA
 88.menu.variant.modelP.build.mcu=atmega88p
 88.menu.variant.modelNonP=88 / 88A
 88.menu.variant.modelNonP.build.mcu=atmega88
 
+# Compiler link time optimization
+88.menu.LTO.Os=Disabled (default)
+88.menu.LTO.Os.compiler.c.extra_flags=
+88.menu.LTO.Os.compiler.c.elf.extra_flags=
+88.menu.LTO.Os.compiler.cpp.extra_flags=
+88.menu.LTO.Os.ltoarcmd=avr-ar
+
+88.menu.LTO.Os_flto=Enabled
+88.menu.LTO.Os_flto.compiler.c.extra_flags=-Wextra -flto
+88.menu.LTO.Os_flto.compiler.c.elf.extra_flags=-w -flto
+88.menu.LTO.Os_flto.compiler.cpp.extra_flags=-Wextra -flto
+88.menu.LTO.Os_flto.ltoarcmd=avr-gcc-ar
 
+# Clock frequencies
 #make atmega88p AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 #make atmega88 AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 88.menu.clock.16MHz_external=16 MHz external (BOD 2.7v)
@@ -271,7 +329,9 @@ menu.BOD=B.O.D
 88.menu.clock.1MHz_internal.build.f_cpu=1000000L
 
 
-############################################################
+##########################
+#### ATmega48/A/P/PA ####
+##########################
 
 48.name=ATmega48 (no bootloader)
 48.upload.tool= avrdude
@@ -287,12 +347,26 @@ menu.BOD=B.O.D
 48.build.board=AVR_ATmega48
 48.build.variant=standard
 
+# Variants
 48.menu.variant.modelP=48P / 48PA
 48.menu.variant.modelP.build.mcu=atmega48p
 48.menu.variant.modelNonP=48 / 48A
 48.menu.variant.modelNonP.build.mcu=atmega48
 
+# Compiler link time optimization
+48.menu.LTO.Os=Disabled (default)
+48.menu.LTO.Os.compiler.c.extra_flags=
+48.menu.LTO.Os.compiler.c.elf.extra_flags=
+48.menu.LTO.Os.compiler.cpp.extra_flags=
+48.menu.LTO.Os.ltoarcmd=avr-ar
+
+48.menu.LTO.Os_flto=Enabled
+48.menu.LTO.Os_flto.compiler.c.extra_flags=-Wextra -flto
+48.menu.LTO.Os_flto.compiler.c.elf.extra_flags=-w -flto
+48.menu.LTO.Os_flto.compiler.cpp.extra_flags=-Wextra -flto
+48.menu.LTO.Os_flto.ltoarcmd=avr-gcc-ar
 
+# Clock frequencies
 #make atmega48p AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 #make atmega48 AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 48.menu.clock.16MHz_external=16 MHz external (BOD 2.7v)
@@ -357,8 +431,10 @@ menu.BOD=B.O.D
 48.menu.clock.1MHz_internal.bootloader.file=empty/empty.hex
 48.menu.clock.1MHz_internal.build.f_cpu=1000000L
 
-############################################################
 
+###################
+#### ATmega8/A ####
+###################
 
 8.name=ATmega8
 8.upload.tool=avrdude
@@ -375,8 +451,20 @@ menu.BOD=B.O.D
 8.build.variant=standard
 8.build.mcu=atmega8
 
+# Compiler link time optimization
+8.menu.LTO.Os=Disabled (default)
+8.menu.LTO.Os.compiler.c.extra_flags=
+8.menu.LTO.Os.compiler.c.elf.extra_flags=
+8.menu.LTO.Os.compiler.cpp.extra_flags=
+8.menu.LTO.Os.ltoarcmd=avr-ar
 
+8.menu.LTO.Os_flto=Enabled
+8.menu.LTO.Os_flto.compiler.c.extra_flags=-Wextra -flto
+8.menu.LTO.Os_flto.compiler.c.elf.extra_flags=-w -flto
+8.menu.LTO.Os_flto.compiler.cpp.extra_flags=-Wextra -flto
+8.menu.LTO.Os_flto.ltoarcmd=avr-gcc-ar
 
+# Clock frequencies
 #make atmega8 AVR_FREQ=16000000L BAUD_RATE=115200 LED=B5 LED_START_FLASHES=2
 8.menu.clock.16MHz_external=16 MHz external (BOD 2.7v)
 8.menu.clock.16MHz_external.upload.speed=115200

diff --git a/avr/platform.txt b/avr/platform.txt
@@ -26,7 +26,7 @@ compiler.c.elf.cmd=avr-gcc
 compiler.S.flags=-c -g -x assembler-with-cpp
 compiler.cpp.cmd=avr-g++
 compiler.cpp.flags=-c -g -Os {compiler.warning_flags} -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD
-compiler.ar.cmd=avr-ar
+compiler.ar.cmd={ltoarcmd}
 compiler.ar.flags=rcs
 compiler.objcopy.cmd=avr-objcopy
 compiler.objcopy.eep.flags=-O ihex -j .eeprom --set-section-flags=.eeprom=alloc,load --no-change-warnings --change-section-lma .eeprom=0