[PATCH] D158476: [driver] Search for compatible Android runtime directories

Wed Aug 23 11:38:32 PDT 2023

smeenai added a comment.

In D158476#4609243 <https://reviews.llvm.org/D158476#4609243>, @srhines wrote:

> This approach LGTM, assuming that https://reviews.llvm.org/D140925 lands as well to ensure that the triple does use `androideabi`, since it would prevent custom build setups from needing additional help.

@phosek is working on that one, but I think this is useful even without it, because you just need to use `android` in your triple when building the runtimes, and can use `androideabi` everywhere else. I'll put up an example runtimes build setup with that to demonstrate.

>> (Aside: why do we need to produce runtime libraries for different versions in the first place? We want one for the minimum OS version we support, of course, but then there's important additions like version 29 adding ELF TLS support and version 31 adding a thread properties API used by LSAN, so building libraries targeting those important versions and having them be dynamically selected based on your target OS version is super useful. We could build the runtime libraries for every single OS version we wanted to support, but that's a lot of versions (at least 21 through 31, times four architectures), which is wasteful for both build times and toolchain distribution size.)
>
> I don't think we need all the versions, but today we really only use 21 (lowest level), and 30 (a conservative level for the platform that supports all our apexes). Ideally we'd also pick up the latest platform version, and we probably should explicitly call out 29 for ELF TLS, so that would be ~4 supported levels, but maybe we can use 29 instead of 30 to cut it to ~3 for most architectures.

Ah, yeah, https://reviews.llvm.org/D85927 dynamically detects the thread properties API, so we don't need an explicit build for 31. An explicit build with ELF TLS is still required though.

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