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RTL slot allocation: Don't kill variables that flow into loops

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* module/language/cps/dfg.scm (dead-after-use?): Don't kill a variable
  if it was defined outside the current loop.
  (dead-after-branch?): Likewise, but I don't think this helper is
  correct yet :/
This commit is contained in:
Andy Wingo 2013-10-12 16:22:45 +02:00
parent 0e2446d4db
commit b8da548fba
1 changed files with 25 additions and 16 deletions
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23
module/language/cps/dfg.scm
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@ -708,17 +708,22 @@
(($ $use-map sym def uses) (($ $use-map sym def uses)
(null? uses)))))) (null? uses))))))
(define (lookup-loop-header k blocks)
(block-loop-header (lookup-block k blocks)))
(define (dead-after-use? sym use-k dfg) (define (dead-after-use? sym use-k dfg)
(match dfg (match dfg
(($ $dfg conts blocks use-maps) (($ $dfg conts blocks use-maps)
(match (lookup-use-map sym use-maps) (match (lookup-use-map sym use-maps)
(($ $use-map sym def uses) (($ $use-map sym def uses)
;; If all other uses dominate this use, it is now dead. There ;; If all other uses dominate this use, and the variable was not
;; are other ways for it to be dead, but this is an ;; defined outside the current loop, it is now dead. There are
;; approximation. A better check would be if all successors ;; other ways for it to be dead, but this is an approximation.
;; post-dominate all uses. ;; A better check would be if all successors post-dominate all
(and-map (cut dominates? <> use-k blocks) ;; uses.
uses)))))) (and (eqv? (lookup-loop-header use-k blocks)
(lookup-loop-header def blocks))
(and-map (cut dominates? <> use-k blocks) uses)))))))
;; A continuation is a "branch" if all of its predecessors are $kif ;; A continuation is a "branch" if all of its predecessors are $kif
;; continuations. ;; continuations.
@ -746,6 +751,10 @@
(($ $dfg conts blocks use-maps) (($ $dfg conts blocks use-maps)
(match (lookup-use-map sym use-maps) (match (lookup-use-map sym use-maps)
(($ $use-map sym def uses) (($ $use-map sym def uses)
;; As in dead-after-use?, we don't kill the variable if it was
;; defined outside the current loop.
(and (eqv? (lookup-loop-header branch blocks)
(lookup-loop-header def blocks))
(and-map (and-map
(lambda (use-k) (lambda (use-k)
;; A symbol is dead after a branch if at least one of the ;; A symbol is dead after a branch if at least one of the
@ -755,7 +764,7 @@
other-branches) other-branches)
(not (dominates? branch use-k blocks)) (not (dominates? branch use-k blocks))
(dominates? use-k branch blocks))) (dominates? use-k branch blocks)))
uses)))))) uses)))))))
(define (lookup-bound-syms k dfg) (define (lookup-bound-syms k dfg)
(match dfg (match dfg