Rustc 1.12.0 Windows build of `ethcore` crate fails with LLVM error

[rphmeier]

Error produced:

EH pad must be jumped to via an unwind edge
  %cleanuppad13 = cleanuppad within none []
  br i1 %1927, label %bb99, label %bb102_cleanup_trampoline_bb99, !dbg !719592

As seen here: https://ci.appveyor.com/project/NikolayVolf/parity-g802m/build/1.3.0+1997#L640
Triggered by this update from 1.10.0 to 1.12.0: https://github.com/ethcore/parity/pull/2423

Either LLVM is broken or the generated IR is.
Feel free to change the title to something more descriptive. Unfortunately I haven't got a windows machine for testing, just the one broken appveyor build.

[alexcrichton]

Historically most of these have been LLVM bugs, unfortunately, which are notoriously hard to track down. @rphmeier do you know if it'd be possible to minimize the test case at all?

[rphmeier]

@alexcrichton yikes, I have no idea to be honest. Like I said, I haven't got a windows machine to test with and the test case as it stands is about 10-15k LoC on its own...

[nikomatsakis]

This may well be related to MIR, as well.

cc @rust-lang/compiler

[rphmeier]

Confirmed a MIR issue: build succeeds with RUSTFLAGS= -Zorbit=off
https://ci.appveyor.com/project/NikolayVolf/parity-g802m/build/1.3.0+2055

[nikomatsakis]

@rphmeier I am trying to get a windows setup up and going to test this and other reported problems (my previous Windows VM recently mysteriously lost its Network Driver and I've never been able to figure out how to get it back...). Any tips you can give me for reproducing it? I guess just a vanilla x86_64 MSVC configuration?

[rphmeier]

@nikomatsakis Thanks for looking into this. A vanilla x86_64 MSVC setup sounds right. The appveyor.yml contains a few additional setup steps which you might find useful: https://github.com/ethcore/parity/blob/master/appveyor.yml

[nikomatsakis]

So I am able to reproduce this. Interestingly, debug builds don't seem to encounter the issue.

[nikomatsakis]

Huh, somewhat frustratingly, this...stopped reproducing for now. Not sure what is different now!