Add CompilerConfig opt to disable IR verification in debug mode

[MarkMcCaskey]

Resolves #1330

Review

• Add a short description of the the change to the CHANGELOG.md file

[nlewycky]

How about enable_verifier = cfg!(test) || cfg!(debug_assertions)?

[MarkMcCaskey]

That would require duplicating that boolean expression because it needs to be checked on the other case too! I considered it but decided against it

[nlewycky]

Is there anything stopping us from turning verification on in a release build? Say, for users who are prepared to spend extra compile-time for extra assurance? If we can do that, could we make this control the setting unilaterally, and also remove the negative?

[syrusakbary]

Yup, agreed with Nick. Since debug verification is probably always false, we can do something like:

Suggested change

	pub disable_debug_mode_verification: bool,
	pub enable_ir_verification: bool,

(note: this can work for both Cranelift and LLVM, since they both have IR verifiers).

[nlewycky]

I'd like to rename it to something like "extra_safety_checks" or "backend_internal_verification" or something along those lines. There's nothing special about clif/llvm here, singlepass could have its own safety checks too, and it doesn't have an IR.

[syrusakbary]

What about enable_internal_verification or enable_verification (I kind of like keeping backend out, since this might be a setting on the backend config itself?)

[MarkMcCaskey]

It's phrased in the negative because we derive(Default) which means it defaults to false haha. I can make a manual implementation of Default though

[nlewycky]

Optional.
⛳ builder.set("enable_verifier", if enable_verifier { "true" } else { "false" }).unwrap();

[nlewycky]

Couldn't you use ..Default::default() for these?

[MarkMcCaskey]

That would infinite loop I believe! My understanding of what ..Default::default() does is that it calls default on the type you're constructing and then overrides the fields you specified. Because we're defining default, I don't believe we can use that syntax here.

[MarkMcCaskey]

Yeah, just verified this:

warning: function cannot return without recursing
   --> lib/runtime-core/src/backend.rs:159:5
    |
159 |     fn default() -> Self {
    |     ^^^^^^^^^^^^^^^^^^^^ cannot return without recursing
...
178 |             ..Default::default()
    |               ------------------ recursive call site
    |
    = note: `#[warn(unconditional_recursion)]` on by default
    = help: a `loop` may express intention better if this is on purpose

[MarkMcCaskey]

bors r+

[bors]

Timed out

[MarkMcCaskey]

bors retry

[bors]

Build succeeded

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