Code change:
# 32/64-bit MinGW builds. # <del> # The MinGW builds unfortunately have to both download a custom toolchain and # avoid the one installed by AppVeyor by default. Interestingly, though, for # different reasons! </del> <ins> # We are using MinGW with posix threads since LLVM does not compile with # the win32 threads version due to missing support for C++'s std::thread. </ins> # <del> # For 32-bit the installed gcc toolchain on AppVeyor uses the pthread # threading model. This is unfortunately not what we want, and if we compile # with it then there's lots of link errors in the standard library (undefined # references to pthread symbols). # # For 64-bit the installed gcc toolchain is currently 5.3.0 which # unfortunately segfaults on Windows with --enable-llvm-assertions (segfaults # in LLVM). See rust-lang/rust#28445 for more information, but to work around # this we go back in time to 4.9.2 specifically. </del> <ins> # Instead of relying on the MinGW version installed on appveryor we download # and install one ourselves so we won't be surprised by changes to appveyor's # build image. </ins> # # Finally, note that the downloads below are all in the `rust-lang-ci` S3 # bucket, but they cleraly didn't originate there! The downloads originally # came from the mingw-w64 SourceForge download site. Unfortunately # SourceForge is notoriously flaky, so we mirror it on our own infrastructure. <del> # # And as a final point of note, the 32-bit MinGW build using the makefiles do # *not* use debug assertions and llvm assertions. This is because they take # too long on appveyor and this is tested by rustbuild below. </del> - MSYS_BITS: 32 RUST_CONFIGURE_ARGS: --build=i686-pc-windows-gnu --enable-ninja SCRIPT: python x.py test MINGW_URL: https://s3.amazonaws.com/rust-lang-ci/rust-ci-mirror <del> MINGW_ARCHIVE: i686-6.2.0-release-win32-dwarf-rt_v5-rev1.7z </del> <ins> MINGW_ARCHIVE: i686-6.2.0-release-posix-dwarf-rt_v5-rev1.7z </ins> MINGW_DIR: mingw32 - MSYS_BITS: 64 SCRIPT: python x.py test RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-gnu --enable-ninja MINGW_URL: https://s3.amazonaws.com/rust-lang-ci/rust-ci-mirror <del> MINGW_ARCHIVE: x86_64-6.2.0-release-win32-seh-rt_v5-rev1.7z </del> <ins> MINGW_ARCHIVE: x86_64-6.2.0-release-posix-seh-rt_v5-rev1.7z </ins> MINGW_DIR: mingw64 # 32/64 bit MSVC and GNU deployment

Related discussion:
text: I'm looking through the AVR-Rust commits and I'd love to coordinate --- feel free to ping me on IRC () or via mail!
Note that there is a regression reported against llvm 4.0 regarding the powi intrinsic on armhf targets: I'm explicitly mentioning this here, because there were previously problems with it, see and related issues. Also cc rust-lang-nursery/compiler-builtins, an issue about the same problem in the compiler-rt rust port.
To clarify what I think the is referring to (correct me if I'm wrong) In LLVM 3.9 and before, the calling convention LLVM used with the powidf2 and powisf2 intrinsics was basically the C calling convention In LLVM 4.0, the backend was corrected to expect these intrinsics to have the aapcs calling convention One person that aapcs is expected for powis2f and powid2f, while another a claiming that the normal C calling convention should be used. So it seems that if the LLVM change is not reverted (expected powisf2 to be aapcs) then we need to update our definition. This is going to be a huge PITA for supporting multiple LLVM versions as well. We need to select the calling convention depending on the LLVM version as well...
Any objections to doing that coordination here on GitHub, or on one of our forks?
I don't have strong preferences for the communication channel.
should address what is listed as API changes" above (the core of the change is in how attributes are represented).
I would prefer to upstream LLVM 4.0 compatibility patches sooner rather than later. That includes my own work obviously, but I'm also looking at the commits I cherry-picked from AVR-Rust. In particular, looks like a reasonable simplification even independent of LLVM 4.0 compatibility, and looks like a nice little self-contained fix. Could you create PRs for those? (If you don't have the time but are otherwise fine with upstreaming, I'd be happy to manage that, giving proper credit of course.)
Absolutely! I wasn't really sure how much we could expect LLVM 4 to change as it goes towards stable / how much churn the Rust maintainers would want to put up with. I'll get those pulled out and submitted soon. I think I'm also starting to understand some of the silly error handling that the new LLVM does.