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fix pessimism in optimizer reordering

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When determing whether expressions can be reordered, a reference to a
module-defined variable was considered unreorderable when it is
known to have a value and no further mutation, but the value isn't
constant across all runs.
This commit is contained in:
Matthew Flatt 2015-03-26 08:23:15 -06:00
parent 21d925d1f0
commit 2dd29f7e3d
2 changed files with 36 additions and 2 deletions
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34
pkgs/racket-test-core/tests/racket/optimize.rktl
View File

@ -1847,6 +1847,40 @@
'(lambda (z)
(list (list (z 2)) (list z))))
(test-comp '(module m racket/base
;; Reference to a ready module-level variable shouldn't
;; prevent let-values splitting
(#%plain-module-begin
(define z (random))
(define (f)
(let-values ([(a b) (values (cons 1 z) (cons 2 z))])
(list a b)))))
'(module m racket/base
;; Reference to a ready module-level variable shouldn't
;; prevent let-values splitting
(#%plain-module-begin
(define z (random))
(define (f)
(list (cons 1 z) (cons 2 z))))))
(test-comp '(module m racket/base
;; Don't reorder references to a mutable variable
(#%plain-module-begin
(define z (random))
(define (f)
(let-values ([(a b) (values (cons 1 z) (cons 2 z))])
(list a b)))
(set! z 5)))
'(module m racket/base
;; Reference to a ready module-level variable shouldn't
;; prevent let-values splitting
(#%plain-module-begin
(define z (random))
(define (f)
(list (cons 1 z) (cons 2 z)))
(set! z 5)))
#f)
(test-comp '(lambda (z)
;; It's ok to reorder unsafe operations relative
;; to each other:

4
racket/src/racket/src/optimize.c
View File

@ -341,9 +341,9 @@ int scheme_omittable_expr(Scheme_Object *o, int vals, int fuel, int resolved,
if (vtype == scheme_compiled_toplevel_type) {
note_match(1, vals, warn_info);
if ((vals == 1) || (vals < 0)) {
if (!no_id && (SCHEME_TOPLEVEL_FLAGS(o) & SCHEME_TOPLEVEL_FLAGS_MASK) >= SCHEME_TOPLEVEL_READY)
if (!no_id && ((SCHEME_TOPLEVEL_FLAGS(o) & SCHEME_TOPLEVEL_FLAGS_MASK) >= SCHEME_TOPLEVEL_READY))
return 1;
else if ((SCHEME_TOPLEVEL_FLAGS(o) & SCHEME_TOPLEVEL_FLAGS_MASK) >= SCHEME_TOPLEVEL_CONST)
else if ((SCHEME_TOPLEVEL_FLAGS(o) & SCHEME_TOPLEVEL_FLAGS_MASK) >= SCHEME_TOPLEVEL_FIXED)
return 1;
else
return 0;