What's the best `target-cpu` option for s390x cross-compiling?

1

What's a suitable -Ctarget-cpu=... for s390x cross-compiling target. Like below

[target.'cfg(target_arch="s390x")']
rustflags = ["-Ctarget-cpu=???", "-Ztune-cpu=???"]
[target.'cfg(all(target_arch="s390x",target_os="linux"))']
linker = "s390x-linux-gnu-gcc"
2

No idea, but you can list the available cpus with rustc --print target-cpus. This should help you narrow it down.

3

I tried, but can't find any similar name match s390 IBM power or something else, not sure this is the full list of supported cpus.

For example if cross-compiling to riscv64gc target, you should pass generic-rv64 to target-cpu, but there is NO riscv* or rv* items in rustc --print target-cpus list.

4

I found the right way to find available target-cpu list for specific target rustc --target=${TRIPLE} --print target-cpus

5

--print target-cpus by default lists the host cpu models. try use the --target xxx flag for cross compiling targets, e.g.

$ rustc --target riscv64gc-unknown-linux-gnu --print target-cpus
# or
$ rustc --target s390x-unknown-linux-gnu --print target-cpus
1 Like
6

Note that if all you need is a suitable target-cpu, you should just be able to leave it out completely. The compiler has a default built-in; the reason to choose a non-default option is if you know that you're running on a specific generation of CPU, in which case @nerditation's suggestion of rustc --target s390x-unknown-linux-gnu --print target-cpus will help you find out how to spell the appropriate CPU generation in terms rustc likes.

7

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