AMD Zen 5 Compiler Support Posted For GCC - Confirms New AVX Features & More

[coder]

Processor-specific tunings are a pox and cancer and should never exist on anything except purpose-built appliances that exist to do only a very specific function.

Everything else should be on -march=x86-64 -mtune=generic

IMO, most of the benchmarks on sites like Phoronix should use generic targets, but if/when someone can safely use native tuning, it makes a lot of sense to do so.

It's only through architecture-specific tuning that the compiler can know which instruction sequences or optimizations to prefer and which to avoid.

[Sonadow]

IMO, most of the benchmarks on sites like Phoronix should use generic targets, but if/when someone can safely use native tuning, it makes a lot of sense to do so.

It's only through architecture-specific tuning that the compiler can know which instruction sequences or optimizations to prefer and which to avoid.

Have fun dealing with illegal instructions when copying a binary built on a one processor over to a computer running on another processor.

[S.Pam]

Processor-specific tunings are a pox and cancer and should never exist on anything except purpose-built appliances that exist to do only a very specific function.

Everything else should be on -march=x86-64 -mtune=generic

That's just weird. The context was a user who recompiles his own software to optimise for his platform. That's the definition of purpose built, isn't it?

[S.Pam]

Have fun dealing with illegal instructions when copying a binary built on a one processor over to a computer running on another processor.

This rarely works on Linux anyway unless you have either exactly the same version of libraries or a statically built binary.

What's wrong with compiling for your hardware as long as you are aware that changing CPU to a lesser/older version might not work so good?

[coder]

Have fun dealing with illegal instructions when copying a binary built on a one processor over to a computer running on another processor.

I know exactly what the downsides are, and I wouldn't do this in a context where I might ever want to run those binaries on a different machine, much less an older or otherwise inferior one.

Furthermore, I've got some news that sounds like it just might blow your friggin' mind! I actually have machines of multiple ISAs on my network, and I compile code on each of them! Oh noessS!!! The horror! Whatever should I do if I somehow copy over a binary executable to a machine of a different ISA??? Oh, the humanity!
🤯 😱

[coder]

This rarely works on Linux anyway unless you have either exactly the same version of libraries or a statically built binary.

Depends. For C++ code, APIs tend not to be designed in a forward-compatible fashion. However, UNIX has a fairly rich tradition of semantic versioning and C libraries which properly implement it.

If you bring your fragile libraries with the executable (or just statically link them, license-permitting), you can be quite successful in running old binaries on a newer kernel and libc.

[Sonadow]

This rarely works on Linux anyway unless you have either exactly the same version of libraries or a statically built binary.

What's wrong with compiling for your hardware as long as you are aware that changing CPU to a lesser/older version might not work so good?

Good. Please rebuild your current Linux distribution entirely from scratch to target your CPU with -march=native

[S.Pam]

Good. Please rebuild your current Linux distribution entirely from scratch to target your CPU with -march=native

Of course. I'm using Gentoo, so that's a given.

[krishoza]

I think the only userspace instruction additions are AVX-512.

https://www.anandtech.com/show/17585...the-high-end/7

However, Zen 4 includes more than the Skylake-level AVX-512 functionality found in v4.

https://en.wikipedia.org/wiki/AVX-512#CPUs_with_AVX-512

That said, I'm not sure how much benefit you'll get from those other extensions, aside from in software packages specifically optimized for them.

Also, using -mtune=znver4 could enable instruction cost tables specific to zen 4, depending on whether AMD ever got around to contributing them. Note that -mtune is implied by -march (for x86, at least; I think it's not true for ARM).

For this statement

Note that -mtune is implied by -march (for x86, at least; I think it's not true for ARM).

is there any compiler documentation which I can take a look at as to for what all compiler this statement is always True