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constraint: Improve assignment lambda handling.

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Assignment lambdas have first order control flow like let lambdas
do. So we can just do global constraint propagation around their
blocks like normal instead of having to reason about higher-order
control flow through local calls.

This speeds things up by not having to do conset bookkeeping in local
calls and stopping the leading blocks optimization. Possibly as a
consequence, it also seems to derive more constraints this way as
shown in the attached test case.

In any case, this is clearly how assignment lambdas should be
handled (by that I mean the same type propagation logic as with other
local call function kinds, but without needing higher order control
flow reasoning), so mark the old TODO item around assignment lambdas
as finished.
This commit is contained in:
Charles Zhang 2026-09-03 01:32:48 +02:00
parent 1ac5b145ea
commit 4a1cbf4f1a
2 changed files with 70 additions and 26 deletions
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59
src/compiler/constraint.lisp
View file

@ -15,7 +15,7 @@
;;;
;;; -- documentation
;;;
;;; -- MV-BIND, :ASSIGNMENT
;;; -- MV-BIND
;;;
;;; Note: The functions in this file that accept constraint sets are
;;; actually receiving the constraint sets associated with nodes,
@ -1337,6 +1337,27 @@
(when lambda-var
(add-eql-var-var-constraint var lambda-var constraints target))))
;;; This function adds appropriate constraints on VARS from a local
;;; call with arguments ARGS into the conset TARGET. Since local calls
;;; can participate in recursive dataflow, we clear any variable
;;; constraints before adding new ones.
(defun constraint-propagate-from-args (args vars constraints target)
(loop for var in vars
for val in args
when (and val (lambda-var-constraints var))
do (conset-clear-lambda-var target var)
(let* ((arg-var (ok-lvar-lambda-var val constraints))
(type (if arg-var
;; Not strictly necessary to grab the
;; type from constraints here straight
;; away, but speeds up convergence.
(type-from-constraints arg-var constraints (lvar-type val))
(lvar-type val))))
(when (type-for-constraints-p type)
(conset-add-constraint target 'typep var type nil))
(when arg-var
(inherit-constraints (list var) arg-var constraints target)))))
;;; Local propagation
;;; -- [TODO: For any LAMBDA-VAR ref with a type check, add that
;;; constraint.]
@ -1436,33 +1457,16 @@
(conset-add-constraint gen 'typep var type nil)))
(maybe-add-eql-var-var-constraint var val gen)
(add-var-result-constraints var val gen)))
((nil assignment optional cleanup)
((assignment)
;; TODO: mv-combinations are too hairy.
(when (combination-p node)
(constraint-propagate-from-args args vars (copy-conset gen) gen)))
((nil optional cleanup)
;; TODO: mv-combinations are too hairy.
(when (combination-p node)
;; Add type constraints and any equality constraints
;; from local call arguments. We clear the existing
;; variable constraints first for local calls which
;; participate in recursive dataflow. (e.g. an iterative
;; loop written functionally instead of with SETQ)
(let ((new (copy-conset gen))
(call-in (combination-constraints-in node)))
(loop for var in vars
for val in args
when (and val (lambda-var-constraints var))
do (conset-clear-lambda-var new var)
(let* ((arg-var (ok-lvar-lambda-var val gen))
(type (if arg-var
;; Not strictly necessary
;; to grab the type from
;; constraints here
;; straight away, but
;; speeds up convergence.
(type-from-constraints arg-var gen (lvar-type val))
(lvar-type val))))
(when (type-for-constraints-p type)
(conset-add-constraint new 'typep var type nil))
(when arg-var
(inherit-constraints (list var) arg-var gen new))))
(constraint-propagate-from-args args vars gen new)
(unless (and call-in (conset= call-in new))
(setf (combination-constraints-in node) new)
(when *constraint-blocks-p*
@ -1626,7 +1630,10 @@
(cond
;; Use constraints from the local calls to this function
((and (bind-p bind)
(functional-kind-eq (bind-lambda bind) nil assignment optional cleanup))
;; LETs and ASSIGNMENTs have first order control flow
;; (their function heads are no longer linked to the
;; component head) so don't need special treatment here.
(functional-kind-eq (bind-lambda bind) nil optional cleanup))
(let ((fun (bind-lambda bind)))
(loop for ref in (lambda-refs fun)
for call = (node-dest ref)
@ -1677,7 +1684,7 @@
(bind (block-start-node block))
fun)
(if (and (bind-p bind)
(functional-kind-eq (setf fun (bind-lambda bind)) nil assignment optional cleanup))
(functional-kind-eq (setf fun (bind-lambda bind)) nil optional cleanup))
(loop for ref in (lambda-refs fun)
for call = (node-dest ref)
for call-block = (and call

37
tests/constraint.pure.lisp
View file

@ -943,6 +943,43 @@
nil))
0)))
(with-test (:name :bounds-check-make-array.ssa)
(assert (= (count 'sb-kernel:%check-bound
(ctu:ir1-named-calls
`(lambda (length)
(declare (integer length))
(let ((array (make-array length)))
(labels ((loop-fn (i)
(when (< i length)
(setf (aref array i) i)
(loop-fn (1+ i)))))
(loop-fn 0))))
nil))
0))
#-sbcl
(assert (= (count 'sb-kernel:%check-bound
(ctu:ir1-named-calls
`(lambda (length)
(let ((array (make-array length)))
(labels ((loop-fn (i)
(when (< i length)
(setf (aref array i) i)
(loop-fn (1+ i)))))
(loop-fn 0))))
nil))
0))
(assert (= (count 'sb-kernel:%check-bound
(ctu:ir1-named-calls
`(lambda (type length)
(let ((array (make-sequence type length)))
(labels ((loop-fn (i)
(when (< i length)
(setf (aref array i) i)
(loop-fn (1+ i)))))
(loop-fn 0))))
nil))
0)))
(with-test (:name :bounds-check-down)
(assert (= (count 'sb-kernel:%check-bound
(ctu:ir1-named-calls