riscv64: Add Newtype Wrappers for Register Classes#6459
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`gen_select_reg` can only compare X registers, but can move F registers based on that decision. Adjust the type signature to reflect that. Also add some lowering tests to cover these cases.
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Can we leave this open overnight to let the fuzzer have some time to explore this? I'm not totally confident that the existing tests explore all of this. (i.e. see the latest commit about |
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Fuzzing hasn't caught anything else, so I think this is probably ok to merge. |
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👋 Hey,
This PR is a followup to a suggestion made by @alexcrichton, it adds newtype wrappers for the different register classes that we have in the RISC-V Backend.
These are
XReg,FRegandVReg, for Integer, Float and Vector. The newtypes are contained only to the ISLE layer, and do not propagate throughout the rest of the backend. However It would be a good idea to iteratively do so, I just felt that it would be too big a step for a first PR.This change was further complicated by a rule that we have in the backend where we auto convert
ValueRegsintoReg. This rule has caused issues in the past (1, 2), and was also conflicting with the newtype wrappers. Instead of adding similar rules to the newtypes, I've removed the rule and all usages of it.Most of this change was in
ext_int_if_needwhich returns ValueRegs, but most of its uses don't actually need more than one register. To that end I've repurposed thezextandsextrules, to act as single register zero or sign extends, and replaced the uses where only one register was necessary with those. Extends that do need multiple registers can useext_int_if_needorextend.These changes haven't changed any of the golden lowerings, but since it's such a broad change, I suspect we might be missing some coverage and I'm going to be fuzzing this overnight to doublecheck.