+;;; ir1opt usually takes care of forwarding let-bound values directly
+;;; to their destination when possible. However, locall analysis
+;;; greatly benefits from that transformation, and is executed in a
+;;; distinct phase from ir1opt. After let-conversion, variables
+;;; bound to functional values are immediately substituted away.
+;;;
+;;; When called from locall, component is non-nil, and the functionals
+;;; are marked for reanalysis when appropriate.
+(defun substitute-let-funargs (call fun component)
+ (declare (type combination call) (type clambda fun)
+ (type (or null component) component))
+ (loop for arg in (combination-args call)
+ and var in (lambda-vars fun)
+ ;; only do that in the absence of assignment
+ when (and arg (null (lambda-var-sets var)))
+ do
+ (binding* ((use (lvar-uses arg))
+ (() (ref-p use) :exit-if-null)
+ (leaf (ref-leaf use))
+ (done-something nil))
+ ;; unlike propagate-let-args, we're only concerned with
+ ;; functionals.
+ (cond ((not (functional-p leaf)))
+ ;; if the types match, we can mutate refs to point to
+ ;; the functional instead of var
+ ((csubtypep (single-value-type (node-derived-type use))
+ (leaf-type var))
+ (let ((use-component (node-component use)))
+ (substitute-leaf-if
+ (lambda (ref)
+ (cond ((eq (node-component ref) use-component)
+ (setf done-something t))
+ (t
+ (aver (lambda-toplevelish-p (lambda-home fun)))
+ nil)))
+ leaf var)))
+ ;; otherwise, we can still play LVAR-level tricks for single
+ ;; destination variables.
+ ((and (singleton-p (leaf-refs var))
+ ;; Don't substitute single-ref variables on high-debug /
+ ;; low speed, to improve the debugging experience.
+ (not (preserve-single-use-debug-var-p call var)))
+ (setf done-something t)
+ (substitute-single-use-lvar arg var)))
+ ;; if we've done something, the functional may now be used in
+ ;; more analysis-friendly manners. Enqueue it if we're in
+ ;; locall.
+ (when (and done-something
+ component
+ (member leaf (component-lambdas component)))
+ (pushnew leaf (component-reanalyze-functionals component)))))
+ (values))
+