Improve the Makefile speed by simple assignment

[eastWillow]

Why

I Live in slow and bad network environments, recursive variable assignments (=) in the Makefile can cause shell commands, such as wget for LINUX_DATA, to execute multiple times, significantly slowing down the build process.

How

By using simple assignment (:=), wget is executed only once during Makefile parsing. This reduces redundant network requests and improves overall Makefile execution speed.

How to Debug

make check SHELL="/bin/bash -x -e -o pipefail"

Before

Terminal Output

+ uname -s
+ uname -m
+ which sha1sum
+ which sha256sum
+ cc --version
+ grep emcc
+ head -n 1
+ cc --version
+ grep clang
+ head -n 1
+ cc --version
+ grep 'Free Software Foundation'
+ uname -m
+ which sdl2-config
+ pkg-config --exists SDL2_mixer
+ echo 0
+ mktemp
+ mktemp
+ mkdir -p /tmp/linux
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x
+ grep -o 'linux-6.1.[0-9]\+\.tar.gz'
+ sort -V
+ tail -n 1
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x
+ grep -o 'linux-6.1.[0-9]\+\.tar.gz'
+ sort -V
+ tail -n 1
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x
+ grep -o 'linux-6.1.[0-9]\+\.tar.gz'
+ sort -V
+ tail -n 1
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x
+ grep -o 'linux-6.1.[0-9]\+\.tar.gz'
+ sort -V
+ tail -n 1
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x/sha256sums.asc
+ awk '{print $1}'
+ grep linux-6.1.157.tar.gz
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x
+ grep -o 'linux-6.1.[0-9]\+\.tar.gz'
+ sort -V
+ tail -n 1
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x
+ grep -o 'linux-6.1.[0-9]\+\.tar.gz'
+ sort -V
+ tail -n 1
+ mkdir -p /home/eastwillow/Documents/RISC-V/rv32emu/build/linux-x86-softfp /home/eastwillow/Documents/RISC-V/rv32emu/build/riscv32 /home/eastwillow/Documents/RISC-V/rv32emu/build/linux-image
+ echo '\033[33mPrebuilt benchmark is found. Skipping downloading.\033[0m\n'
\033[33mPrebuilt benchmark is found. Skipping downloading.\033[0m\n
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x
+ grep -o 'linux-6.1.[0-9]\+\.tar.gz'
+ sort -V
+ tail -n 1

After

Terminal Output

+ uname -s
+ uname -m
+ which sha1sum
+ which sha256sum
+ cc --version
+ head -n 1
+ grep emcc
+ cc --version
+ grep clang
+ head -n 1
+ cc --version
+ grep 'Free Software Foundation'
+ uname -m
+ which sdl2-config
+ pkg-config --exists SDL2_mixer
+ echo 0
+ mktemp
+ mktemp
+ mkdir -p /tmp/linux
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x
+ sort -V
+ grep -o 'linux-6.1.[0-9]\+\.tar.gz'
+ tail -n 1
+ wget -q -O- https://cdn.kernel.org/pub/linux/kernel/v6.x/sha256sums.asc
+ grep linux-6.1.157.tar.gz
+ awk '{print $1}'
+ mkdir -p /home/eastwillow/Documents/RISC-V/rv32emu/build/linux-x86-softfp /home/eastwillow/Documents/RISC-V/rv32emu/build/riscv32 /home/eastwillow/Documents/RISC-V/rv32emu/build/linux-image
+ echo '\033[33mPrebuilt benchmark is found. Skipping downloading.\033[0m\n'

References

• GNU Make Manual: Simple Assignment
• Makefile 語法和示範

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Summary by cubic

Switch LINUX_DATA and LINUX_DATA_SHA to simple assignment (:=) so wget runs once at parse time. This prevents repeated downloads and speeds up builds, especially on slow networks.

[cubic-dev-ai]

No issues found across 1 file

[jserv]

Avoid inserting screenshots that contain only plain text, as visually impaired individuals may be unable to perceive or understand their content.

[jserv]

Thank @eastWillow for contributing!

[eastWillow]

Avoid inserting screenshots that contain only plain text, as visually impaired individuals may be unable to perceive or understand their content.

OK, I will modify the content.