Tracking Issue for f16b

This is a tracking issue for the RFC "bf16 type" (rust-lang/rfcs#3983). The feature gate for the issue is #![feature(f16b)].

Approved by the language team for experimentation in the 2026/08/06 triage meeting.

This feature is part of the "f16b" project goal from 2026 (rust-lang/goals#757). It was discussed by the language team in the 2026/08/06 design meeting. It is currently being worked on by @Jamesbarford.

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

• Rename everything to f16b from bf16
• Implement the RFC (rust-lang/rust#160859)
• Add Neon and SVE intrinsics using f16b
• Revisit RFC for final approval
• Adjust documentation (see instructions on rustc-dev-guide)
• Style updates for any new syntax (nightly-style-procedure)
  • Style team decision on new formatting
  • Formatting for new syntax has been added to the Style Guide
  • (non-blocking) Formatting has been implemented in rustfmt
• Stabilization PR (see instructions on rustc-dev-guide)

Unresolved Questions

• What to do about the ABI on targets without a defined f16b calling convention?

Implementation history

• rust-lang/rust#160859

Start by reading the linked RFC and implementation issue rust-lang/rust#160859, then review the remaining checklist items for intrinsics, documentation, style updates, and stabilization. Done means the RFC is implemented, the listed follow-up work is addressed, and the unresolved ABI question has a decision.