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CSE can run on first-order CPS

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* module/language/cps/cse.scm (compute-truthy-expressions):
  (compute-equivalent-subexpressions):
  (eliminate-common-subexpressions): Refactor to be able to work on
  first-order CPS.
This commit is contained in:
Andy Wingo 2015-10-28 09:13:20 +00:00
parent 8d79dfddb6
commit 04356dabb9
1 changed files with 148 additions and 164 deletions
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312
module/language/cps/cse.scm
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@ -123,7 +123,7 @@ an intset containing ancestor labels whose value is available at LABEL."
(intset kfun)
(intmap-add empty-intmap kfun empty-intset)))
(define (compute-truthy-expressions conts kfun boolv)
(define (compute-truthy-expressions conts kfun)
"Compute a \"truth map\", indicating which expressions can be shown to
be true and/or false at each label in the function starting at KFUN..
Returns an intmap of intsets. The even elements of the intset indicate
@ -177,24 +177,13 @@ false. It could be that both true and false proofs are available."
(propagate1 kbody)))
(($ $ktail) (propagate0)))))
(let ((boolv (worklist-fold* visit-cont
(intset kfun)
(intmap-add boolv kfun empty-intset))))
;; Now visit nested functions. We don't do this in the worklist
;; folder because that would be exponential.
(define (recurse kfun boolv)
(compute-truthy-expressions conts kfun boolv))
(intset-fold
(lambda (label boolv)
(match (intmap-ref conts label)
(($ $kargs _ _ ($ $continue _ _ exp))
(match exp
(($ $fun kfun) (recurse kfun boolv))
(($ $rec _ _ (($ $fun kfun) ...)) (fold recurse boolv kfun))
(_ boolv)))
(_ boolv)))
(compute-function-body conts kfun)
boolv)))
(intset-fold
(lambda (kfun boolv)
(worklist-fold* visit-cont
(intset kfun)
(intmap-add boolv kfun empty-intset)))
(intmap-keys (compute-reachable-functions conts kfun))
empty-intmap))
(define (intset-map f set)
(persistent-intmap
@ -236,151 +225,147 @@ false. It could be that both true and false proofs are available."
(intset-subtract (persistent-intset single)
(persistent-intset multiple)))))
(define (compute-equivalent-subexpressions conts kfun effects
equiv-labels var-substs)
(let* ((succs (compute-successors conts kfun))
(singly-referenced (compute-singly-referenced succs))
(avail (compute-available-expressions conts kfun effects))
(defs (compute-defs conts kfun))
(equiv-set (make-hash-table)))
(define (subst-var var-substs var)
(intmap-ref var-substs var (lambda (var) var)))
(define (subst-vars var-substs vars)
(let lp ((vars vars))
(match vars
(() '())
((var . vars) (cons (subst-var var-substs var) (lp vars))))))
(define (compute-equivalent-subexpressions conts kfun effects)
(define (visit-fun kfun equiv-labels var-substs)
(let* ((succs (compute-successors conts kfun))
(singly-referenced (compute-singly-referenced succs))
(avail (compute-available-expressions conts kfun effects))
(defs (compute-defs conts kfun))
(equiv-set (make-hash-table)))
(define (subst-var var-substs var)
(intmap-ref var-substs var (lambda (var) var)))
(define (subst-vars var-substs vars)
(let lp ((vars vars))
(match vars
(() '())
((var . vars) (cons (subst-var var-substs var) (lp vars))))))
(define (compute-exp-key var-substs exp)
(match exp
(($ $const val) (cons 'const val))
(($ $prim name) (cons 'prim name))
(($ $fun body) #f)
(($ $rec names syms funs) #f)
(($ $call proc args) #f)
(($ $callk k proc args) #f)
(($ $primcall name args)
(cons* 'primcall name (subst-vars var-substs args)))
(($ $branch _ ($ $primcall name args))
(cons* 'primcall name (subst-vars var-substs args)))
(($ $branch) #f)
(($ $values args) #f)
(($ $prompt escape? tag handler) #f)))
(define (compute-exp-key var-substs exp)
(match exp
(($ $const val) (cons 'const val))
(($ $prim name) (cons 'prim name))
(($ $fun body) #f)
(($ $rec names syms funs) #f)
(($ $closure label nfree) #f)
(($ $call proc args) #f)
(($ $callk k proc args) #f)
(($ $primcall name args)
(cons* 'primcall name (subst-vars var-substs args)))
(($ $branch _ ($ $primcall name args))
(cons* 'primcall name (subst-vars var-substs args)))
(($ $branch) #f)
(($ $values args) #f)
(($ $prompt escape? tag handler) #f)))
(define (add-auxiliary-definitions! label var-substs exp-key)
(define (subst var)
(subst-var var-substs var))
(let ((defs (intmap-ref defs label)))
(define (add-def! aux-key var)
(let ((equiv (hash-ref equiv-set aux-key '())))
(hash-set! equiv-set aux-key
(acons label (list var) equiv))))
(match exp-key
(('primcall 'box val)
(match defs
((box)
(add-def! `(primcall box-ref ,(subst box)) val))))
(('primcall 'box-set! box val)
(add-def! `(primcall box-ref ,box) val))
(('primcall 'cons car cdr)
(match defs
((pair)
(add-def! `(primcall car ,(subst pair)) car)
(add-def! `(primcall cdr ,(subst pair)) cdr))))
(('primcall 'set-car! pair car)
(add-def! `(primcall car ,pair) car))
(('primcall 'set-cdr! pair cdr)
(add-def! `(primcall cdr ,pair) cdr))
(('primcall (or 'make-vector 'make-vector/immediate) len fill)
(match defs
((vec)
(add-def! `(primcall vector-length ,(subst vec)) len))))
(('primcall 'vector-set! vec idx val)
(add-def! `(primcall vector-ref ,vec ,idx) val))
(('primcall 'vector-set!/immediate vec idx val)
(add-def! `(primcall vector-ref/immediate ,vec ,idx) val))
(('primcall (or 'allocate-struct 'allocate-struct/immediate)
vtable size)
(match defs
((struct)
(add-def! `(primcall struct-vtable ,(subst struct))
vtable))))
(('primcall 'struct-set! struct n val)
(add-def! `(primcall struct-ref ,struct ,n) val))
(('primcall 'struct-set!/immediate struct n val)
(add-def! `(primcall struct-ref/immediate ,struct ,n) val))
(_ #t))))
(define (add-auxiliary-definitions! label var-substs exp-key)
(define (subst var)
(subst-var var-substs var))
(let ((defs (intmap-ref defs label)))
(define (add-def! aux-key var)
(let ((equiv (hash-ref equiv-set aux-key '())))
(hash-set! equiv-set aux-key
(acons label (list var) equiv))))
(match exp-key
(('primcall 'box val)
(match defs
((box)
(add-def! `(primcall box-ref ,(subst box)) val))))
(('primcall 'box-set! box val)
(add-def! `(primcall box-ref ,box) val))
(('primcall 'cons car cdr)
(match defs
((pair)
(add-def! `(primcall car ,(subst pair)) car)
(add-def! `(primcall cdr ,(subst pair)) cdr))))
(('primcall 'set-car! pair car)
(add-def! `(primcall car ,pair) car))
(('primcall 'set-cdr! pair cdr)
(add-def! `(primcall cdr ,pair) cdr))
(('primcall (or 'make-vector 'make-vector/immediate) len fill)
(match defs
((vec)
(add-def! `(primcall vector-length ,(subst vec)) len))))
(('primcall 'vector-set! vec idx val)
(add-def! `(primcall vector-ref ,vec ,idx) val))
(('primcall 'vector-set!/immediate vec idx val)
(add-def! `(primcall vector-ref/immediate ,vec ,idx) val))
(('primcall (or 'allocate-struct 'allocate-struct/immediate)
vtable size)
(match defs
((struct)
(add-def! `(primcall struct-vtable ,(subst struct))
vtable))))
(('primcall 'struct-set! struct n val)
(add-def! `(primcall struct-ref ,struct ,n) val))
(('primcall 'struct-set!/immediate struct n val)
(add-def! `(primcall struct-ref/immediate ,struct ,n) val))
(_ #t))))
(define (visit-label label equiv-labels var-substs)
(match (intmap-ref conts label)
(($ $kargs names vars ($ $continue k src exp))
(let* ((exp-key (compute-exp-key var-substs exp))
(equiv (hash-ref equiv-set exp-key '()))
(fx (intmap-ref effects label))
(avail (intmap-ref avail label)))
(define (finish equiv-labels var-substs)
(define (recurse kfun equiv-labels var-substs)
(compute-equivalent-subexpressions conts kfun effects
equiv-labels var-substs))
;; If this expression defines auxiliary definitions,
;; as `cons' does for the results of `car' and `cdr',
;; define those. Do so after finding equivalent
;; expressions, so that we can take advantage of
;; subst'd output vars.
(add-auxiliary-definitions! label var-substs exp-key)
(match exp
;; If we see a $fun, recurse to add to the result.
(($ $fun kfun)
(recurse kfun equiv-labels var-substs))
(($ $rec names vars (($ $fun kfun) ...))
(fold2 recurse kfun equiv-labels var-substs))
(_
(values equiv-labels var-substs))))
(let lp ((candidates equiv))
(match candidates
(()
;; No matching expressions. Add our expression
;; to the equivalence set, if appropriate. Note
;; that expressions that allocate a fresh object
;; or change the current fluid environment can't
;; be eliminated by CSE (though DCE might do it
;; if the value proves to be unused, in the
;; allocation case).
(when (and exp-key
(not (causes-effect? fx &allocation))
(not (effect-clobbers? fx (&read-object &fluid))))
(let ((defs (and (intset-ref singly-referenced k)
(intmap-ref defs label))))
(when defs
(hash-set! equiv-set exp-key
(acons label defs equiv)))))
(finish equiv-labels var-substs))
(((and head (candidate . vars)) . candidates)
(cond
((not (intset-ref avail candidate))
;; This expression isn't available here; try
;; the next one.
(lp candidates))
(else
;; Yay, a match. Mark expression as equivalent. If
;; we provide the definitions for the successor, mark
;; the vars for substitution.
(finish (intmap-add equiv-labels label head)
(let ((defs (and (intset-ref singly-referenced k)
(intmap-ref defs label))))
(if defs
(fold (lambda (def var var-substs)
(intmap-add var-substs def var))
var-substs defs vars)
var-substs))))))))))
(_ (values equiv-labels var-substs))))
(define (visit-label label equiv-labels var-substs)
(match (intmap-ref conts label)
(($ $kargs names vars ($ $continue k src exp))
(let* ((exp-key (compute-exp-key var-substs exp))
(equiv (hash-ref equiv-set exp-key '()))
(fx (intmap-ref effects label))
(avail (intmap-ref avail label)))
(define (finish equiv-labels var-substs)
;; If this expression defines auxiliary definitions,
;; as `cons' does for the results of `car' and `cdr',
;; define those. Do so after finding equivalent
;; expressions, so that we can take advantage of
;; subst'd output vars.
(add-auxiliary-definitions! label var-substs exp-key)
(values equiv-labels var-substs))
(let lp ((candidates equiv))
(match candidates
(()
;; No matching expressions. Add our expression
;; to the equivalence set, if appropriate. Note
;; that expressions that allocate a fresh object
;; or change the current fluid environment can't
;; be eliminated by CSE (though DCE might do it
;; if the value proves to be unused, in the
;; allocation case).
(when (and exp-key
(not (causes-effect? fx &allocation))
(not (effect-clobbers? fx (&read-object &fluid))))
(let ((defs (and (intset-ref singly-referenced k)
(intmap-ref defs label))))
(when defs
(hash-set! equiv-set exp-key
(acons label defs equiv)))))
(finish equiv-labels var-substs))
(((and head (candidate . vars)) . candidates)
(cond
((not (intset-ref avail candidate))
;; This expression isn't available here; try
;; the next one.
(lp candidates))
(else
;; Yay, a match. Mark expression as equivalent. If
;; we provide the definitions for the successor, mark
;; the vars for substitution.
(finish (intmap-add equiv-labels label head)
(let ((defs (and (intset-ref singly-referenced k)
(intmap-ref defs label))))
(if defs
(fold (lambda (def var var-substs)
(intmap-add var-substs def var))
var-substs defs vars)
var-substs))))))))))
(_ (values equiv-labels var-substs))))
;; Traverse the labels in fun in reverse post-order, which will
;; visit definitions before uses first.
(fold2 visit-label
(compute-reverse-post-order succs kfun)
equiv-labels
var-substs)))
;; Traverse the labels in fun in reverse post-order, which will
;; visit definitions before uses first.
(fold2 visit-label
(compute-reverse-post-order succs kfun)
equiv-labels
var-substs)))
(intset-fold visit-fun
(intmap-keys (compute-reachable-functions conts kfun))
empty-intmap
empty-intmap))
(define (apply-cse conts equiv-labels var-substs truthy-labels)
(define (true-idx idx) (ash idx 1))
@ -391,7 +376,7 @@ false. It could be that both true and false proofs are available."
(define (visit-exp exp)
(rewrite-exp exp
((or ($ $const) ($ $prim) ($ $fun) ($ $rec)) ,exp)
((or ($ $const) ($ $prim) ($ $fun) ($ $rec) ($ $closure)) ,exp)
(($ $call proc args)
($call (subst-var proc) ,(map subst-var args)))
(($ $callk k proc args)
@ -442,8 +427,7 @@ false. It could be that both true and false proofs are available."
(call-with-values
(lambda ()
(let ((effects (synthesize-definition-effects (compute-effects conts))))
(compute-equivalent-subexpressions conts 0 effects
empty-intmap empty-intmap)))
(compute-equivalent-subexpressions conts 0 effects)))
(lambda (equiv-labels var-substs)
(let ((truthy-labels (compute-truthy-expressions conts 0 empty-intmap)))
(let ((truthy-labels (compute-truthy-expressions conts 0)))
(apply-cse conts equiv-labels var-substs truthy-labels)))))