Lab 4 - GCC Build Lab (Part 1)

Introduction

This lab focuses on learning how to build the GCC (GNU Compiler Collection) from source code. GCC is a widely used compiler that supports multiple programming languages, including C and C++. Since GCC is a large and complex software project, understanding its build process is essential.


By completing this lab, we will:

• Learn how to obtain, configure, and compile GCC.

• Use common build tools like make, autotools, and configure.

• Gain experience working with large open-source projects.

• Compare build performance on different architectures (x86_64 and AArch64).


For this lab, we will perform the experiment on two SPO600 servers:

1. x86-001 (x86_64 architecture)

2. aarch64-002 (AArch64 architecture)


For now, I will begin with x86-001 and document the process. 








Step 1: Downloading the GCC Source Code

The first step is to obtain the latest GCC development version. The recommended way is to clone the official GCC repository using Git.

mkdir -p ~/git && cd ~/git
git clone https://gcc.gnu.org/git/gcc.git

• mkdir -p ~/git && cd ~/git → Creates a directory named git and moves into it.

• git clone https://gcc.gnu.org/git/gcc.git → Clones the entire GCC repository.

• The cloning process takes time because GCC has a long history and a large number of commits.






Step 2: Checking the Latest Commit

Once cloning is complete, we check the latest commit information. This helps verify that we have successfully obtained the latest development version.

cd ~/git/gcc
git log -1

• git log -1 → Shows details of the most recent commit like this.

commit 67e824c2497176980cb0c5d14bc730fa4ce2e1ad (HEAD -> master, origin/trunk, origin/master, origin/HEAD)

Author: Jeff Law <jlaw@ventanamicro.com>

Date:   Sun Mar 2 12:08:34 2025 -0700


    [RISC-V][PR target/118934] Fix ICE in RISC-V long branch support

    

    I'm not sure if I goof'd this or if I merely upstreamed someone else's goof.

    Either way the long branch code isn't working correctly.

    

    We were using 'n' as the output modifier to negate the condition.  But 'n' has

    a special meaning elsewhere, so when presented with a condition rather than

    what was expected, boom, the compiler ICE'd.

    

    Thankfully there's only a few places where we were using %n which I turned into

    %r.

    

    The BZ entry includes a good testcase, it just takes a long time to compile as

    it's trying to create the out-of-range scenario.  I'm not including the

    testcase due to how long it takes, but I did test it locally to ensure it's

    working properly now.

    

    I'm sure that with a little bit of work I could create at testcase that worked

    before and fails with the trunk (by taking advantage of the fuzzyness in length

    computations).  So I'm going to consider this a regression.

    

    Will push to the trunk after pre-commit testing does its thing.

    

            PR target/118934

    gcc/

            * config/riscv/corev.md (cv_branch): Adjust output template.

            (branch): Likewise.

            * config/riscv/riscv.md (branch): Likewise.

            * config/riscv/riscv.cc (riscv_asm_output_opcode): Handle 'r' rather

            than 'n'.

~


(END)



Step 3: Creating a Build Directory

To avoid modifying the original source code, it is recommended to create a separate build directory.

mkdir ~/gcc-build-001
cd ~/gcc-build-001

• mkdir ~/gcc-build-001 → Creates a new directory where we will compile GCC.

• cd ~/gcc-build-001 → Moves into the build directory.



Step 4: Configuring the GCC Build

Before building GCC, we need to set up the environment by running the configure script.

~/git/gcc/configure --prefix=$HOME/gcc-test-001

• ~/git/gcc/configure → Runs the configuration script from the GCC source directory.

• --prefix=$HOME/gcc-test-001 → Specifies where GCC should be installed after compilation.

• If any missing dependencies are reported, they need to be installed before proceeding.

• Running ls -l ~/gcc-build-001/Makefile should confirm that a Makefile was generated.




Step 5: Building GCC

Now that everything is set up, we can start the build process using make.

cd ~/gcc-build-001
time make -j 24 |& tee build.log

• make -j 24 → Starts the build process with 24 parallel jobs (for faster compilation).

• time → Measures how long the build takes.

• tee build.log → Saves both the output and errors to build.log.

• The build can take a long time (possibly over an hour).

• Using screen or tmux allows disconnecting and reconnecting while the build runs.

• If any errors occur, checking build.log will help with debugging.



To be continued in next posting!



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