Tracking Issue for `movrs` target feature

[sayantn]

Feature gate: #![feature(movrs_target_feature)]

This is a tracking issue for the x86(64) target feature movrs. It includes 2 instructions - MOVRS and PREFETCHRST2. These behave as normal MOV and PREFETCHW instructions, just with the "read-shared" hint. This, as suggested by the name, is purely a hint to the processor that the data loaded/stored by the instruction is likely to get accessed by multiple processors.

Public API

The movrs target feature (which enables the MOVRS and PREFETCHRST2 instructions) and the following stdarch intrinsics

• _movrs_i8
• _movrs_i16
• _movrs_i32
• _movrs_i64
• _m_prefetchrs

Steps / History

• Implementation
• Final comment period (FCP)¹
• Stabilization PR

Implementation History

• Add the new amx target features and the movrs target feature #138003
• Add runtime detection for new AMX variants and MOVRS stdarch#1763

Unresolved Questions

• How does this interact with the memory model? The Intel specification strongly suggests that this is just a hint to the processor, but we need to check to be sure.

Footnotes

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩