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Support instructions that clobber all registers and have non-fixed uses

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#145 2 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
rust
Domain
compilers

Research direction

Start by tracing the existing special cases for fixed-register uses that clobber the register, then reproduce the TooManyLiveRegisters failure for an unconstrained use that clobbers all registers. Done means regalloc2 handles that instruction without requiring an unnecessary fixed-register constraint.

Written by the indexing model from the issue text.

Description

There are currently special cases for when an instruction uses a fixed register and clobbers it, but when an instruction uses an unconstrained register and clobbers all registers there is no special case and we get a TooManyLiveRegisters error. This can be avoided by adding an unnecessary fixed register constraint so that the first special case is hit, but one shouldn't have to constrain the register allocation in that way, regalloc2 should just handle this case.

Dominant language
Rust
Stars
266
Forks
54
No merged PRs in 30d

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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