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- Log -
commit 238ef4cf4413e407d1d61e379b690310f7383605
Author: Andy Wingo wi...@pobox.com
Date: Fri Oct 11 14:10:19 2013 +0200
Replace conservatively-dominates? with a precise dominator lookup
* module/language/cps/dfg.scm (dominates?): Use the dominator tree
instead of the scope tree.
---
Summary of changes:
module/language/cps/dfg.scm | 26 +-
1 files changed, 13 insertions(+), 13 deletions(-)
diff --git a/module/language/cps/dfg.scm b/module/language/cps/dfg.scm
index 667d822..fe5c245 100644
--- a/module/language/cps/dfg.scm
+++ b/module/language/cps/dfg.scm
@@ -486,15 +486,15 @@
uses))
;; Does k1 dominate k2?
-;;
-;; Note that this is a conservative predicate: a false return value does
-;; not indicate that k1 _doesn't_ dominate k2. The reason for this is
-;; that we are using the scope tree as an approximation of the dominator
-;; relationship. See
-;; http://mlton.org/pipermail/mlton/2003-January/023054.html for a
-;; deeper discussion.
-(define (conservatively-dominates? k1 k2 blocks)
- (continuation-scope-contains? k1 k2 blocks))
+(define (dominates? k1 k2 blocks)
+ (match (lookup-block k1 blocks)
+(($ $block _ _ _ _ k1-idom k1-dom-level)
+ (match (lookup-block k2 blocks)
+ (($ $block _ _ _ _ k2-idom k2-dom-level)
+(cond
+ (( k1-dom-level k2-dom-level) #f)
+ (( k1-dom-level k2-dom-level) (dominates? k1 k2-idom blocks))
+ ((= k1-dom-level k2-dom-level) (eqv? k1 k2
(define (dead-after-def? sym dfg)
(match dfg
@@ -512,7 +512,7 @@
;; are other ways for it to be dead, but this is an
;; approximation. A better check would be if the successor
;; post-dominates all uses.
-(and-map (cut conservatively-dominates? use-k blocks)
+(and-map (cut dominates? use-k blocks)
uses))
;; A continuation is a branch if all of its predecessors are $kif
@@ -546,10 +546,10 @@
;; A symbol is dead after a branch if at least one of the
;; other branches dominates a use of the symbol, and all
;; other uses of the symbol dominate the test.
- (if (or-map (cut conservatively-dominates? use-k blocks)
+ (if (or-map (cut dominates? use-k blocks)
other-branches)
- (not (conservatively-dominates? branch use-k blocks))
- (conservatively-dominates? use-k branch blocks)))
+ (not (dominates? branch use-k blocks))
+ (dominates? use-k branch blocks)))
uses))
(define (lookup-bound-syms k dfg)
hooks/post-receive
--
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