Better Continuation aliases #3210
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Feb 5, 2025
Replace the continuation alias mechanism with a more general continuation shortcut mechanism. A continuation shortcut is a let_cont whose body is an arbitrary apply_cont. A continuation alias is a special case of continuation shortcuts where the arguments of the apply_cont are exactly the parameters of the let_cont. Shortcuts are detected and resolved in the upwards pass after rewriting the apply_cont, so that we should never output code containing continuation shortcuts (except when used as return or exception continuation). This should help generate simpler control flow for later Simplify or To_cmm passes, and make the output of `-dflambda` easier to follow. Fixes ocaml-flambda#3210
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Currently continuation aliases are quite restrictive: they only apply when a continuation [k]'s handler is exactly an apply_cont of another continuation [k'] with exactly the same arguments, of the form:
let_cont k x_1 ... x_n = apply_cont k' x_1 .... x_n. In that case, the continuation alias mechanism replaces calls to [k] by calls to [k'] during the upwards pass.This is quite restrictive, and actually, we could substitute any continuation [k] whose handler is only an apply_cont, after applying the required renaming and reordering of params/arguments (plus addition of constants arguments), so that we could do the substitution in the following case:
let_cont k x y = apply_cont k' y 0 x.The text was updated successfully, but these errors were encountered: