Documentation

Remove unused let-bindings

The Let handler of deadCode.

Flatten's letrecs after inlineCleanup

inlineCleanup sometimes exposes additional possibilities for caseCon, which then introduces let-bindings in what should be ANF. This transformation flattens those nested let-bindings again.

NB: must only be called in the cleaning up phase.

The Let handler of flattenLet; recurses on the rebuilt let-expression after merging nested bindings.

Turn a normalized recursive function, where the recursive calls only pass along the unchanged original arguments, into let-recursive function. This means that all recursive calls are replaced by the same variable reference as found in the body of the top-level let-expression.

The Case handler of removeUnusedExpr: a single-alternative case whose pattern binds no used variables is replaced by the alternative.

The application-spine handlers of removeUnusedExpr: replace unused arguments of primitives (and Vecs Cons) with removedArg.

Simplified CSE, only works on let-bindings, does an inverse topological sort of the let-bindings and then works from top to bottom

XXX: Check whether inverse top-sort followed by single traversal removes as many binders as the previous "apply-until-fixpoint" approach in the presence of recursive groups in the let-bindings. If not but just for checking whether changes to transformation affect the eventual size of the circuit, it would be really helpful if we tracked circuit size in the regression/test suite. On the two examples that were tested, Reducer and PipelinesViaFolds, this new version of CSE removed the same amount of let-binders.

The Let handler of simpleCSE.

Ensure that top-level lambda's eventually bind a let-expression of which the body is a variable-reference.

The worker of topLet: a plain rewrite, offered at every node.