Accept AnyValue in PhiValue::replace_all_uses_with

[bjorn3]

Description

Allow replacing a PhiValue with any value kind, not just another PhiValue. This is necessary to be able to use a PhiValue as placeholder until the value is actually defined when translating from another SSA form ir like Cranelift ir.

Related Issue

Fixes https://github.com/TheDan64/inkwell/issues/272

How This Has Been Tested

Option<Breaking Changes>

I don't think this breaks anything as PhiValue implements AnyValue.

Checklist

• [x] I have read the Contributing Guide

[TheDan64]

Hi @bjorn3 sorry that this is taken so long to get merged. Could you please 1) rebase this PR and 2) explain how this is valid? If the IR expects a phi value, wouldn't replacing it with another type potentially break the code?

[bjorn3]

sorry that this is taken so long to get merged.

No worries.

If the IR expects a phi value, wouldn't replacing it with another type potentially break the code?

In my case other code doesn't expect a phi value. It expects any kind of value. It is just the case that I need a dummy value as placeholder (https://github.com/bjorn3/wasmtime/blob/0bb1639f68ba46d20919e2a8c4e83f8d20d19917/cranelift/llvm/src/function.rs#L205) until it gets replaced with the actual value (https://github.com/bjorn3/wasmtime/blob/0bb1639f68ba46d20919e2a8c4e83f8d20d19917/cranelift/llvm/src/function.rs#L221) once the defining block gets lowered. Phi instructions are the only instructions I could find that are suitable as placeholder for any type of value. If you have a suggestion for a better alternative, please tell me.

[TheDan64]

I'm not totally sure what the correct answer is for your situation, but something about it does seem odd 🤔