Tracking Issue for s390x_target_feature

[RalfJung]

This is a tracking issue for s390x_target_feature, guarding target features on s390x.
This is a catch-all issue for all target features on that target. See this file for a list of target features currently guarded by this feature gate.

See #44839 for discussion from before this feature got its own tracking issue.

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.
Discussion comments will get marked as off-topic or deleted.
Repeated discussions on the tracking issue may lead to the tracking issue getting locked.

Steps

• Figure out ABI interactions and other possible blockers/concerns
• Move target features that should not be part of the initial stabilization under separate feature gates
• Final Comment Period (FCP)
• Stabilization PR (see instructions on rustc-dev-guide)

Unresolved Questions

• Enabling backchain on a per-function basis does not make a lot of sense. Maybe it should be a -C flag instead? Or a target feature that we only allow with -Ctarget-feature and cfg!(target_feature) but not #[target_feature] (something that has no precedent)? Also see the discussion here.

Implementation history