[OpenPower-Firmware] [RFC] Rework op-build to sdk efficiency

[Klaus Heinrich Kiwi]

On 5/13/2020 7:07 PM, Klaus Heinrich Kiwi wrote:
> Presently, op-build builds buildroot's default cross-compiling 
> toolchain, that can be made into an SDK and re-used. We use this as part 
> of the ci build scripts (ci/build*.sh), but that mechanism can also be 
> used ad-hoc.
> 
> I recently pushed some patches to try to slim it down for efficiency 
> (PRs #3586), and now I'm trying to add the p8-PORE (for POWER8) and 
> PPE42-{gcc/PORE-binutils} (for POWER9) as part of the sdk package, so 
> they can also be re-used (they rarely change).


Any feedback on this PR? Otherwise I'll merge it
https://github.com/open-power/op-build/pull/3625

> This is accomplished by creating a pair of "toolchain" virtual-packages, 
> and creating builtin providers (the packages above themselves) and 
> "external" providers (as part of the sdk) and wiring it all together.
> 
> Initial testing looks promising. I haven't timed the before/after build 
> times yet, but I could already verify that it's sensibly faster when 
> caching the SDK and re-building the tree. And hopefully it's also safer 
> to use in CI (versus for example partially building a tree in a 
> workspace and re-using that instead).
> 
> But it's a significant change, so I'd appreciate more eyes reviewing and 
> testing it, here or on the PR itself (currently in draft mode):
> https://github.com/open-power/op-build/pull/3625
> 
> A potential next step might be in identifying other similar 
> "toolchain-like" packages that rarely change, and could benefit from the 
> same treatment (finding the right balance between building them on the 
> SDK versus as part of the build tree).
> 
> Thanks,
> 
>   -Klaus

-- 
Klaus Heinrich Kiwi <klaus at linux.vnet.ibm.com>