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| author | Kaz Kylheku <kaz@kylheku.com> | 2021-03-10 08:09:08 -0800 |
|---|---|---|
| committer | Kaz Kylheku <kaz@kylheku.com> | 2021-03-10 08:09:08 -0800 |
| commit | 631dc14534aef3fa17feb3864aedaa9a4292e796 (patch) | |
| tree | aae7c0c3ed91d40784f1c98699e322a0123fdc6c | |
| parent | bb526b11ed93a0853eecac8bb5d0588bec61e837 (diff) | |
| download | txr-631dc14534aef3fa17feb3864aedaa9a4292e796.tar.gz txr-631dc14534aef3fa17feb3864aedaa9a4292e796.tar.bz2 txr-631dc14534aef3fa17feb3864aedaa9a4292e796.zip | |
compiler: eliminate unused closures.
In this patch, we optimize away closures that are not used.
Unused closures that have been hoisted to the top level are
not affected. We look for close instructions which produce
a dead treg, and rewrite these to jmp instructions to the same
label. When this happend, we set a flag for a dead code
elimination pass to be done again, to actually remove the now
unreachable closure code.
* share/txr/stdlib/optimize.tl (struct basic-blocks): New
slot, reelim, indicating that dead code elimination is to be
done again after peephole since the control flow graph has
changed.
(basic-blocks peephole-block): New pattern for eliminating a
dead register, targeting the close instruction.
(basic-blocks peephole): After peephole, check whether the
reelim flag has been set and do elim-dead-code again.
| -rw-r--r-- | share/txr/stdlib/optimize.tl | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/share/txr/stdlib/optimize.tl b/share/txr/stdlib/optimize.tl index 8f166a6f..109dc9b3 100644 --- a/share/txr/stdlib/optimize.tl +++ b/share/txr/stdlib/optimize.tl @@ -57,6 +57,7 @@ list rescan recalc + reelim (:static start (gensym "start-")) (:static jump-ops '(jmp if ifq ifql close swtch ret abscsr uwprot catch block jend)) @@ -359,6 +360,12 @@ (pushnew bl bb.rescan) (set bb.recalc t) (cdr insns)) + (@(require ((close (t @n) @nil @nil @jlabel . @nil) . @nil) + (dead-treg (car insns) n)) + (pushnew bl bb.rescan) + (set bb.recalc t + bb.reelim t) + ^((jmp ,jlabel) ,*(cdr insns))) (@(require ((@(or gcall gapply) (t @n) @idx . @nil) . @nil) (dead-treg (car insns) n) [%const-foldable% [bb.symvec idx]]) @@ -436,7 +443,9 @@ bb.(calc-liveness rescan) (set bb.recalc nil)) (each ((bl rescan)) - (set bl.insns bb.(peephole-block bl bl.insns))))) + (set bl.insns bb.(peephole-block bl bl.insns)))) + (when bb.reelim + bb.(elim-dead-code))) (defmeth basic-blocks thread-jumps (bb) (each ((bl bb.list)) |