factor/basis/compiler/cfg/stacks/global/global.factor

! Copyright (C) 2009 Slava Pestov.
! See http://factorcode.org/license.txt for BSD license.
USING: assocs kernel combinators compiler.cfg.dataflow-analysis
compiler.cfg.stacks.local ;
IN: compiler.cfg.stacks.global

: transfer-peeked-locs ( assoc bb -- assoc' )
    [ replace-set assoc-diff ] [ peek-set assoc-union ] bi ;

! A stack location is anticipated at a location if every path from
! the location to an exit block will read the stack location
! before writing it.
BACKWARD-ANALYSIS: anticip

M: anticip-analysis transfer-set drop transfer-peeked-locs ;

! A stack location is live at a location if some path from
! the location to an exit block will read the stack location
! before writing it.
BACKWARD-ANALYSIS: live

M: live-analysis transfer-set drop transfer-peeked-locs ;

M: live-analysis join-sets drop assoc-combine ;

! A stack location is available at a location if all paths from
! the entry block to the location load the location into a
! register.
FORWARD-ANALYSIS: avail

M: avail-analysis transfer-set
    drop [ peek-set assoc-union ] [ replace-set assoc-union ] bi ;

! A stack location is pending at a location if all paths from
! the entry block to the location write the location.
FORWARD-ANALYSIS: pending

M: pending-analysis transfer-set
    drop replace-set assoc-union ;

! A stack location is dead at a location if no paths from the
! location to the exit block read the location before writing it.
BACKWARD-ANALYSIS: dead

M: dead-analysis transfer-set
    drop
    [ kill-set assoc-union ]
    [ replace-set assoc-union ] bi ;

! Main word
: compute-global-sets ( cfg -- cfg' )
    {
        [ compute-anticip-sets ]
        [ compute-live-sets ]
        [ compute-pending-sets ]
        [ compute-dead-sets ]
        [ compute-avail-sets ]
        [ ]
    } cleave ;