Clash.Normalize.DEC

Helper functions for the disjointExpressionConsolidation transformation

The disjointExpressionConsolidation transformation lifts applications of global binders out of alternatives of case-statements.

e.g. It converts:

case x of
  A -> f 3 y
  B -> f x x
  C -> h x

into:

let f_arg0 = case x of {A -> 3; B -> x}
    f_arg1 = case x of {A -> y; B -> x}
    f_out  = f f_arg0 f_arg1
in  case x of
      A -> f_out
      B -> f_out
      C -> h x

Documentation

collectGlobals

Arguments

:: InScopeSet

-> [(Term, Term)]

Substitution of (applications of) a global binder by a reference to a lifted term.

-> [Term]

List of already seen global binders

-> Term

The expression

-> RewriteMonad NormalizeState (Term, InScopeSet, [(Term, ([Term], CaseTree [Either Term Type]))])

Collect CaseTrees for (potentially) disjoint applications of globals out of an expression. Also substitute truly disjoint applications of globals by a reference to a lifted out application.

collectGlobalsArgs

Arguments

:: InScopeSet

-> [(Term, Term)]

Substitution of (applications of) a global binder by a reference to a lifted term.

-> [Term]

List of already seen global binders

-> [Either Term Type]

The list of arguments

-> RewriteMonad NormalizeState ([Either Term Type], InScopeSet, [(Term, ([Term], CaseTree [Either Term Type]))])

Collect CaseTrees for (potentially) disjoint applications of globals out of a list of application arguments. Also substitute truly disjoint applications of globals by a reference to a lifted out application.

isDisjoint :: CaseTree [Either Term Type] -> Bool

Test if a CaseTree collected from an expression indicates that application of a global binder is disjoint: occur in separate branches of a case-expression.

mkDisjointGroup

Arguments

:: InScopeSet

Variables in scope at the very top of the case-tree, i.e., the original expression

-> (Term, ([Term], CaseTree [Either Term Type]))

Case-tree of arguments belonging to the applied term.

-> RewriteMonad NormalizeState (Term, [Term])

Given a case-tree corresponding to a disjoint interesting "term-in-a- function-position", return a let-expression: where the let-binding holds a case-expression selecting between the distinct arguments of the case-tree, and the body is an application of the term applied to the shared arguments of the case tree, and projections of let-binding corresponding to the distinct argument positions.