Set arm-unknown-linux-gnueabihf as alt platform on aarch64

[CallMeFoxie]

Description of the Change
Adds arm-unknown-linux-gnueabihf as alt platform to aarch64*linux-gnu. HF as all armv8+ devices have hard float, plus -gnueabihf is known platform for projects.

Alternate Designs
None

Release Notes
Adds arm-unknown-linux-gnueabihf as alt platform to aarch64*linux-gnu devices.

[truboxl]

Users still need to enable 32bit support in their aarch64 Linux environment, so hooray for one less setup step?

[CallMeFoxie]

You mean libc etc? If the app isn't compiled statically then yeah (WCG is static and runs fine, U@H requires libraries in the OS). isn't the same being done for amd64/i686 though? (lines 26 - 32)

[truboxl]

Ok. BOINC docs also point out on amd64 Linux, some 32bit dependencies are needed to be installed manually.
So LGTM. But I am still skeptical on whether ALL the armv8+ chips support for 32bit still hold true in the future...

[SETIguy]

We test for 32bit environments in 64bit clients and vice versa in order to select the right alternate platforms at runtime under linux x86/x86_64 by looking in likely places (/lib, etc) for 32 or 64 bit libraries. Maybe that should be expanded for aarch64 and arm. Code is in cs_platform.

…

On Wed, Nov 4, 2020 at 7:16 PM Jia Yuan Lo ***@***.***> wrote: Ok. BOINC docs also point out on amd64 Linux, some 32bit dependencies are needed to be installed manually. So LGTM. But I am still skeptical on whether ALL the armv8+ chips support for 32bit still hold true in the future... — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#4081 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACS5ZMWF6GRVUWJOHI2FLJ3SOIKJXANCNFSM4TJWPIHQ> .

-- Eric Korpela korpela@ssl.berkeley.edu AST:7731^29u18e3

[truboxl]

As explained, there are armv8 aarch64 chips that don't support aarch32, so we need to have a test like SETIguy said and not blindly adding support. This is why I oppose it in #3740 for Android. It may happen in 2022 that true 64bit arm processors will arrive.

Here are some supplemental information:
https://www.arm.com/company/news/2020/10/pushing-the-boundaries-of-performance-and-security-to-unleash-the-power-of-64-bit-computing
https://www.xda-developers.com/future-arm-cpu-drop-support-32-bit-apps/
https://stackoverflow.com/questions/65318052/run-armv8-codes-in-m1-chip#comment115484044_65318052
https://stackoverflow.com/questions/64949775/how-to-find-out-if-an-armv8-processor-supports-the-aarch32-execution-state

[CallMeFoxie]

you're right, it should be added. I honestly didn't know about the x86 alt platform code on x86_64, I just went by other platforms code for android :) yeah it should be done by checking for ld-linux at least.