Inline assembly

[Amanieu]

TL;DR

• Implement the new asm! syntax proposed in Inline assembly rfcs#2873.
• The new syntax is much more user-friendly and has significantly more checks in rustc, which should make it impossible to trigger an ICE, unlike the old implementation.

Links and Details

In rust-lang/rust#71007 we deprecated the old asm! macro and told users to use llvm_asm! instead. The next step is to replace asm! with a macro implementing the new syntax proposed in the RFC.

The implementation PR has design notes on how the inline assembly passes through the various stages of the compiler (AST, HIR, MIR, etc).

Implementation PR: rust-lang/rust#69171
New RFC thread: rust-lang/rfcs#2873
Old RFC thread (now closed): rust-lang/rfcs#2850

Mentors or Reviewers

@nagisa has already performed an initial review of the implementation PR.

[nikomatsakis]

@rustbot second

I second this proposal -- basically, everything here looks "roughly like" I would expect it to look, and @nagisa has already done an initial review, so we have a dedicated reviewer.

[nikomatsakis]

FCP expired, closing the issue!