factor/library/compiler/optimizer.factor

224 lines
7.2 KiB
Factor

! :folding=indent:collapseFolds=1:
! $Id$
!
! Copyright (C) 2004 Slava Pestov.
!
! Redistribution and use in source and binary forms, with or without
! modification, are permitted provided that the following conditions are met:
!
! 1. Redistributions of source code must retain the above copyright notice,
! this list of conditions and the following disclaimer.
!
! 2. Redistributions in binary form must reproduce the above copyright notice,
! this list of conditions and the following disclaimer in the documentation
! and/or other materials provided with the distribution.
!
! THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
! INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
! FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
! DEVELOPERS AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
! SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
! PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
! OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
! WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
! OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
! ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
IN: compiler
USE: lists
USE: namespaces
USE: kernel
USE: inference
USE: words
USE: prettyprint
! The optimizer transforms dataflow IR to dataflow IR. Currently
! it removes literals that are eventually dropped, and never
! arise as inputs to any other type of function. Such 'dead'
! literals arise when combinators are inlined and quotations are
! lifted to their call sites. Also, #label nodes are inlined if
! their children do not make a recursive call to the label.
: scan-literal ( node -- )
#! If the node represents a literal push, add the literal to
#! the list being constructed.
"scan-literal" [ drop ] apply-dataflow ;
: (scan-literals) ( dataflow -- )
[ scan-literal ] each ;
: scan-literals ( dataflow -- list )
[ (scan-literals) ] make-list ;
: scan-branches ( branches -- )
#! Collect all literals from all branches.
[ node-param get ] bind [ [ scan-literal ] each ] each ;
: mentions-literal? ( literal list -- ? )
#! Does the given list of result objects refer to this
#! literal?
[ dupd value= ] some? nip ;
: consumes-literal? ( literal node -- ? )
#! Does the dataflow node consume the literal?
[
dup node-consume-d get mentions-literal? swap
dup node-consume-r get mentions-literal? nip or
] bind ;
: produces-literal? ( literal node -- ? )
#! Does the dataflow node produce the literal?
[
dup node-produce-d get mentions-literal? swap
dup node-produce-r get mentions-literal? nip or
] bind ;
: (can-kill?) ( literal node -- ? )
#! Return false if the literal appears as input to this
#! node, and this node is not a stack operation.
2dup consumes-literal? >r produces-literal? r> or not ;
: can-kill? ( literal dataflow -- ? )
#! Return false if the literal appears in any node in the
#! list.
[ dupd "can-kill" [ (can-kill?) ] apply-dataflow ] all? nip ;
: kill-set ( dataflow -- list )
#! Push a list of literals that may be killed in the IR.
dup scan-literals [ over can-kill? ] subset nip ;
: can-kill-branches? ( literal node -- ? )
#! Check if the literal appears in either branch.
2dup consumes-literal? [
2drop f
] [
[ node-param get ] bind [ dupd can-kill? ] all? nip
] ifte ;
: kill-node ( literals node -- )
swap [ over (can-kill?) ] all? [ , ] [ drop ] ifte ;
: (kill-nodes) ( literals dataflow -- )
#! Append live nodes to currently constructing list.
[ dupd "kill-node" [ nip , ] apply-dataflow ] each drop ;
: kill-nodes ( literals dataflow -- dataflow )
#! Remove literals and construct a list.
[ (kill-nodes) ] make-list ;
: optimize ( dataflow -- dataflow )
#! Remove redundant literals from the IR. The original IR
#! is destructively modified.
dup kill-set swap kill-nodes ;
: kill-branches ( literals node -- )
[
node-param [ [ dupd kill-nodes ] map nip ] change
] extend , ;
#push [ [ node-param get ] bind , ] "scan-literal" set-word-property
#push [ consumes-literal? not ] "can-kill" set-word-property
#push [ kill-node ] "kill-node" set-word-property
#label [
[ node-param get ] bind (scan-literals)
] "scan-literal" set-word-property
#label [
[ node-param get ] bind can-kill?
] "can-kill" set-word-property
#call-label [
[ node-param get ] bind =
] "calls-label" set-word-property
: calls-label? ( label list -- ? )
[
dupd "calls-label" [ 2drop f ] apply-dataflow
] some? nip ;
#label [
[ node-param get ] bind calls-label?
] "calls-label" set-word-property
#simple-label [
[ node-param get ] bind calls-label?
] "calls-label" set-word-property
: branches-call-label? ( label list -- ? )
[ dupd calls-label? ] some? nip ;
#ifte [
[ node-param get ] bind branches-call-label?
] "calls-label" set-word-property
#dispatch [
[ node-param get ] bind branches-call-label?
] "calls-label" set-word-property
: optimize-label ( -- op )
#! Does the label node contain calls to itself?
node-label get node-param get calls-label?
#label #simple-label ? ;
#label [ ( literals node -- )
[
optimize-label node-op set
node-param [ kill-nodes ] change
] extend ,
] "kill-node" set-word-property
#ifte [ scan-branches ] "scan-literal" set-word-property
#ifte [ can-kill-branches? ] "can-kill" set-word-property
#ifte [ kill-branches ] "kill-node" set-word-property
#dispatch [ scan-branches ] "scan-literal" set-word-property
#dispatch [ can-kill-branches? ] "can-kill" set-word-property
#dispatch [ kill-branches ] "kill-node" set-word-property
! Don't care about inputs to recursive combinator calls
#call-label [ 2drop t ] "can-kill" set-word-property
#drop [ 2drop t ] "can-kill" set-word-property
#drop [ kill-node ] "kill-node" set-word-property
#dup [ 2drop t ] "can-kill" set-word-property
#dup [ kill-node ] "kill-node" set-word-property
#swap [ 2drop t ] "can-kill" set-word-property
#swap [ kill-node ] "kill-node" set-word-property
: kill-mask ( killing inputs -- mask )
[ over [ over value= ] some? >boolean nip ] map nip ;
: reduce-stack-op ( literals node map -- )
#! If certain values passing through a stack op are being
#! killed, the stack op can be reduced, in extreme cases
#! to a no-op.
-rot [
[ node-consume-d get ] bind kill-mask swap assoc
] keep
over [ [ node-op set ] extend , ] [ 2drop ] ifte ;
#over [ 2drop t ] "can-kill" set-word-property
#over [
[
[ [ f f ] | #over ]
[ [ f t ] | #dup ]
] reduce-stack-op
] "kill-node" set-word-property
#pick [ 2drop t ] "can-kill" set-word-property
#pick [
[
[ [ f f f ] | #pick ]
[ [ f f t ] | #over ]
[ [ f t f ] | #over ]
[ [ f t t ] | #dup ]
] reduce-stack-op
] "kill-node" set-word-property
#>r [ 2drop t ] "can-kill" set-word-property
#>r [ kill-node ] "kill-node" set-word-property
#r> [ 2drop t ] "can-kill" set-word-property
#r> [ kill-node ] "kill-node" set-word-property