Track const type information in a separate lattice element #44447
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Introduces a spearate lattice elements for tracking const Types
that also stores the corresponding Type{} information, ensuring
that this is only computed once and whenever possible is taken
from an existing instance of it instead of recomputing it.
Part of #44402
|
Oh I guess I forgot the punch line. This makes inference 20% faster on my particular inference benchmark. |
vtjnash
reviewed
Mar 8, 2022
| @@ -983,7 +983,10 @@ | |||
| '())) | |||
| ;; otherwise do an assignment to trigger an error | |||
| (= (outerref ,name) ,name))) | |||
| (= (outerref ,name) ,name)) | |||
| (block | |||
| (call (core set_binding_type!) (thismodule) (inert ,name) (call (core apply_type) (core Type) ,name)) | |||
|
IIUC, this was essentially replaced by #44704, before this one became badly conflicted |
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As mentioned in #44402,
widenconston aConstwhose value is aTypecan be quite slow - slow enough to show up noticeably in profiles. This attempts to address that by splitting theConstlattice element into two:ConstandConstType, the former being used for non-Typevalues and the latter being used forTypes, additionally tracking theType{T}for the constant typeT, thus saving the lookup on widenconst.Now, not every
Constactually passes through widenconst, which would cause a performance regression, but it turns out that mostConstTypes originate from global references. Thus, we can take advantage of the recently added binding type field to cache theType{T}value for bindings and directly feed that into ConstType.As a second enhancement, when we don't already have a Type{T} value, we could make the corresponding
ConstTypefield lazily computed on the firstwidenconst. However, because this would requires makingConstTypemutable, this change is a bit of a wash performance wise. I included it in the anticipation that codegen for mutable types with const fields will improve in the future, but it's optional.