[Codegen] Skip wb emission when they are no children objects

[vchuravy]

Originally found by @pchintalapudi

[vtjnash]

Wow, that seemed to cause a surprising amount of CI chaos

[vtjnash]

Bisected this to https://reviews.llvm.org/D106613

[vchuravy]

Adding this to the milestone so that we pick up https://reviews.llvm.org/D106613 at least, even if we don't backport this commit.

[JeffBezanson]

The LLVM patch is probably not release-blocking, since AFAICT we don't actually hit the bug in 1.7. Once it's settled will be good to backport though.

[vtjnash]

FWIW, it seems like we are potentially waiting for the next LLVM version, which disables the offending logic (via a better cost model), since I don't know how to fix it.

[vchuravy]

@nanosoldier runbenchmarks(ALL, vs=":master")

[vchuravy]

@nanosoldier runtests(ALL, vs = ":master")

[nanosoldier]

Something went wrong when running your job:

NanosoldierError: error when preparing/pushing to report repo: failed process: Process(setenv(`git push`; dir="/run/media/system/data/nanosoldier/workdir/NanosoldierReports"), ProcessExited(1)) [1]

Unfortunately, the logs could not be uploaded.
cc @christopher-dG

[nanosoldier]

Your package evaluation job has completed - possible new issues were detected. A full report can be found here.

[vchuravy]

PkgEval failed due to the network outage yesterday...

[vchuravy]

@nanosoldier runtests(ALL, vs = ":master")

[nanosoldier]

Your package evaluation job has completed - possible new issues were detected. A full report can be found here.

[vtjnash]

https://github.com/JuliaCI/NanosoldierReports/blob/master/benchmark/by_hash/3bcac5f_vs_592cacc/report.md