Comparison SEGGER Toolchain and gcc with CMake

General

This article describes the use of the SEGGER Toolchain with CMake and showcases the code-size comparisons between the SEGGER Toolchain (compiler and linker) and the ARM GCC toolchain (compiler and linker).

We have based our internal testing on three different projects:

A FreeRTOS demo that runs on an Atmel/Microchip SAME70_Xplained Ultra board (see below for how to reproduce this on your own)
Our internal embench IOT benchmarking application
Our internal emPower OS demo application

The source code for the comparisons has been kept mostly identical between the ARM GCC and SEGGER Toolchain builds, with the exception of some toolchain-specific code (e.g. startup/initialization code or compiler specific attributes syntax).
All compared builds have been configured to "-Oz" optimization level (which optimizes for size, corresponding to the "*_minsizerel" build presets mentioned below). Furthermore the effect of using Link-Time-Optimization (LTP/IPO) is also shown.
Further optimization of the firmware size is possible beyond what is demonstrated here by applying techniques as described under the article: How to optimize a Firmware for minimal Size
A general guide on how to utilize the SEGGER CMake toolchain is available as a README.md file at https://github.com/SEGGERMicro/segger-toolchain-cmake

Build size comparison tables

The following tables summarize the results we have obtained.

A. Results for the FreeRTOS demo application
	Code				RO-Data				Sum (Code + RO-Data)
	ARM GCC	SEGGER	abs. Diff*	% diff*	ARM GCC	SEGGER	abs. Diff*	% diff*	ARM GCC	SEGGER	abs. Diff*
without LTO	41108	37848	-3260	-7.9%	956	1046	+90	+9.4%	42064	38894	-3170
with LTO	37440	34576	-2864	-7.6%	948	1000	+52	+5.5%	38388	35576	-2812

B. Results for the embench IOT benchmarking application
	Code				RO-Data				Sum (Code + RO-Data)
	ARM GCC	SEGGER	abs. Diff*	% diff*	ARM GCC	SEGGER	abs. Diff*	% diff*	ARM GCC	SEGGER	abs. Diff*
without LTO	83076	75766	-7310	-8.8%	18984	18921	-63	-0.3%	102060	94687	-7373
with LTO	69724	63018	-6706	-9.6%	18772	18791	+19	+0.1%	88496	81809	-6687

C. Results for the emPower OS demo application
	Code				RO-Data				Sum (Code + RO-Data)
	ARM GCC	SEGGER	abs. Diff*	% diff*	ARM GCC	SEGGER	abs. Diff*	% diff*	ARM GCC	SEGGER	abs. Diff*
without LTO	158158	119224	-38934	-24.6%	492640	490511	-2129	-0.4%	650798	609735	-41063
with LTO	143954	106642	-37312	-25.9%	492288	490149	-2139	-0.4%	636242	596791	-39451

Notes:

(diff*): SEGGER build size minus ARM GCC build size

Tool versions for comparison

Following versions have been used for the applications listed above:

SEGGER toolchain: version V8.25 Build 2025090300.59980 - part of SEGGER Embedded Studio, obtainable at https://www.segger.com/downloads/embedded-studio
- Compiler version = 19.1.2

- Linker version = 4.44.2
ARM GCC toolchain: version 14.2.Rel1 - obtainable at https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
- Compiler version = 14.2.1

- Linker version = 2.43.1.20241119
SEGGER CMake toolchain: version 1.2.0 - obtainable at https://github.com/SEGGERMicro/segger-toolchain-cmake
ARM GCC CMake toolchain: version 02dbd14fc6e32aa568eaf8b200cef48b2c6d7b7d (main) - obtainable at https://github.com/vpetrigo/arm-cmake-toolchains.git

Reproducing the results for the FreeRTOS demo

Description of the FreeRTOS demo project

The demo project has been derived from the official FreeRTOS Demo from version 202411.00 and runs on the Atmel/Microchip SAME70_Xplained Ultra board
The original demo description is here http://www.freertos.org/Atmel_SAMV7_Cortex-M7_RTOS_Demo.html.

In comparison with the original demo code, our demo version comes with following changes:

some adaptations for the SEGGER compiler (e.g. for defining __inline__ macros, startup code etc.)
addition of CMakeLists.txt in order to build with both ARM GCC as well as SEGGER on the same code base (with exception of tool-specific startup code)
redefinition of the GPIO-port for the blinking LED such that now LED3 is used.
mainCREATE_SIMPLE_BLINKY_DEMO_ONLY is set to 0: this ensures that the more comprehensive test-set is run as described under http://www.freertos.org/Atmel_SAMV7_Cortex-M7_RTOS_Demo.html
adaptation in the GNU linker script in order to move read-only data from the .text output section into a dedicated output section. Required for better comparison of resulting code and data sizes.

1-Stop ZIP package

A complete 1-stop ZIP package for the demo is available that includes the FreeRTOS kernel in addition to the demo project: Media:FreeRTOS_SGR_20251009_1519.zip

Instructions for the demo

Setup

Download the 1-stop ZIP package from Media:FreeRTOS_SGR_20251009_1519.zip
Unzip the package. This will yield a working folder called "FreeRTOS_SGR".
Under "FreeRTOS_SGR" there are following folders/files of interest:
- Source : this contains the FreeRTOS-kernel.
- Demo : this corresponds in function to the Demo folder found in the official FreeRTOS source code repository. In the demo package it contains only 2 subfolders:
  - Common : copy of the Common folder from the official FreeRTOS source code repository. Required for some basic demo functionality.
  
  - CORTEX_M7_SAME70_Xplained_AtmelStudio : the actuall demo application.
Install required compiler toolchains and other prerequisites:
- Install Ninja: https://ninja-build.org/
- Install CMake: version 3.24 or later: https://cmake.org/download
- Install SEGGER Embedded Studio V8.25: https://www.segger.com/downloads/embedded-studio
- For ARM GCC builds, install ARM GCC version 14.2.Rel1: https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Make sure the PATH environment variable contains the paths to the following:
- cmake executable (at least version 3.24)
- ninjaexecutable
- arm-none-eabi-gcc executable etc. (from your ARM GCC distribution)

Command-line usage

NOTE: issue these commands from within the FreeRTOS_SGR/Demo/CORTEX_M7_SAME70_Xplained_AtmelStudio subfolder!

Check which configuration-presets are available:

$ cmake --list-presets
Available configure presets:

  "sgr_flat_nolto"    - sgr_flat_nolto
  "sgr_flat_lto"      - sgr_flat_lto
  "armgcc_flat_nolto" - armgcc_flat_nolto
  "armgcc_flat_lto"   - armgcc_flat_lto

Check which build-presets are available (their name-endings indicate which kind of build-configurations they perform):

$ cmake --build --list-presets
Available build presets:

  "sgr_flat_nolto_dbg"
  "sgr_flat_nolto_minsizerel"
  "sgr_flat_lto_dbg"
  "sgr_flat_lto_minsizerel"
  "armgcc_flat_nolto_dbg"
  "armgcc_flat_nolto_minsizerel"
  "armgcc_flat_lto_dbg"
  "armgcc_flat_lto_minsizerel"

First execute the configuration step with

cmake --preset <config-preset-name>

Example:

$ cmake --preset sgr_flat_lto
Preset CMake variables:

  CMAKE_CONFIGURATION_TYPES="MinSizeRel;Debug;Release"
  CMAKE_MAKE_PROGRAM="ninja"
  CMAKE_SYSTEM_PROCESSOR="arm-cortex-m7"
  CMAKE_TOOLCHAIN_FILE:FILEPATH="C:/WORK/DEV/PRJ/CMAKE/WRKSPC/FreeRTOS/FreeRTOS_SGR/Demo/CORTEX_M7_SAME70_Xplained_AtmelStudio/cmake_toolchains/segger-toolchain-cmake/segger-toolchain.cmake"
  PROJECT_ENABLE_IPO="1"
  PROJECT_FLAT_SOURCE_LIST="1"

-- CMAKE_MODULE_PATH extended by C:/WORK/DEV/PRJ/CMAKE/WRKSPC/FreeRTOS/FreeRTOS_SGR/Demo/CORTEX_M7_SAME70_Xplained_AtmelStudio/cmake_modules
-- The C compiler identification is SEGGERClang 19.1.2
-- Found binutils: arm-none-eabi
-- The CXX compiler identification is SEGGERClang 19.1.2
-- Found binutils: arm-none-eabi
-- The ASM compiler identification is SEGGERClang
-- Found binutils: arm-none-eabi
-- Found assembler: C:/Program Files/SEGGER/SEGGER Embedded Studio 8.25/bin/cc.exe
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/Program Files/SEGGER/SEGGER Embedded Studio 8.25/bin/cc.exe - skipped
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files/SEGGER/SEGGER Embedded Studio 8.25/bin/cc++.exe - skipped
--
================================================================================================================
SEGGER_CMAKE_TOOLCHAIN_VERSION = 1.2.0
SEGGER_TOOLCHAIN_PKG_ROOT = C:/Program Files/SEGGER/SEGGER Embedded Studio 8.25
SEGGER_CMAKE_HAS_BUILTIN_COMPILER_ID = TRUE
CMAKE_SYSTEM_NAME = Generic
CMAKE_SYSTEM_PROCESSOR = arm-cortex-m7
Available build configuration types = MinSizeRel, Debug, Release
================================================================================================================

Then execute the build step with

cmake --build <build-preset-name>

Example:

$ cmake --build --preset sgr_flat_lto_minsizerel
[22/47] Building C object CMakeFiles/CORTEX_M7_SAME70-FreeRTOS-Demo.dir/MinSizeRel/src/ASF/common/services/serial/usart_serial.o

Visual Studio Code (VS Code) usage

NOTE: open the FreeRTOS_SGR/Demo/CORTEX_M7_SAME70_Xplained_AtmelStudio subfolder as the workspace folder withing VS Code!

When opening the project folder in VS Code for the first time, the CMake extension pops up a drop-down list of configuration-presets to choose from.
The selected configuration-preset is shown in the extensions page. You may also choose another configuration-preset by clicking on the pencil icon.
The currently effective build-preset is shown in the extensions page. You may also choose another build-preset by clicking on the pencil icon.
Click on the build-icon on the "Build" section in order to build the associated artefacts.

Comparison SEGGER Toolchain and gcc with CMake

Contents

General

Build size comparison tables

Tool versions for comparison

Reproducing the results for the FreeRTOS demo

Description of the FreeRTOS demo project

1-Stop ZIP package

Instructions for the demo

Setup

Command-line usage

Visual Studio Code (VS Code) usage

Navigation menu

Comparison SEGGER Toolchain and gcc with CMake

General

Build size comparison tables

Tool versions for comparison

Reproducing the results for the FreeRTOS demo

Description of the FreeRTOS demo project

1-Stop ZIP package

Instructions for the demo

Setup

Command-line usage

Visual Studio Code (VS Code) usage

Navigation menu

Search