##write-barrier
Basic block instructions

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Vocabulary
compiler.cfg.instructions

Class description
An instruction for inserting a write barrier. This instruction is almost always inserted after a ##set-slot instruction. If the container object is in an older generation than the item inserted, this instruction guarantees that the item will not be garbage collected. It has the following slots:

src	Object to which the writer barrier refers.
slot	Slot index of the object.
scale	No idea.
tag	Type tag for obj.
temp1	First temporary register to clobber.
temp2	Second temporary register to clobber.

Definition

IN: compiler.cfg.instructions

TUPLE: ##write-barrier < vreg-insn
    src slot scale tag temp1 temp2 insn# ;

Methods

USING: accessors compiler.cfg.gvn.avail
compiler.cfg.instructions kernel ;

M: ##write-barrier >avail-insn-temps
    [ ] change-temp1 [ ] change-temp2 drop ;


USING: accessors compiler.cfg.gvn.avail
compiler.cfg.instructions kernel ;

M: ##write-barrier >avail-insn-uses
    [ dup >avail-vreg swap or ] change-src
    [ dup >avail-vreg swap or ] change-slot drop ;


USING: accessors compiler.cfg.instructions
compiler.cfg.linear-scan.assignment kernel ;

M: ##write-barrier assign-insn-temps
    [ vreg>reg ] change-temp1 [ vreg>reg ] change-temp2 drop ;


USING: accessors compiler.cfg.instructions
compiler.cfg.linear-scan.assignment kernel ;

M: ##write-barrier assign-insn-uses
    [ vreg>reg ] change-src [ vreg>reg ] change-slot drop ;


USING: accessors compiler.cfg.dce compiler.cfg.instructions
kernel ;

M: ##write-barrier build-liveness-graph
    dup src>> setter-liveness-graph ;


USING: accessors compiler.cfg.dce compiler.cfg.instructions
kernel ;

M: ##write-barrier compute-live-vregs
    dup src>> setter-live-vregs ;


USING: accessors compiler.cfg.instructions
compiler.cfg.representations.rewrite kernel ;

M: ##write-barrier convert-insn-temps
    [ ] change-temp1 [ ] change-temp2 drop ;


USING: accessors compiler.cfg.instructions
compiler.cfg.representations.rewrite kernel ;

M: ##write-barrier convert-insn-uses
    [ converted-value ] change-src
    [ converted-value ] change-slot drop ;


USING: accessors compiler.cfg.instructions
compiler.cfg.write-barrier ;

M: ##write-barrier eliminate-write-barrier
    src>> needs-write-barrier? ;


USING: accessors compiler.cfg.instructions compiler.codegen
cpu.architecture kernel ;

M: ##write-barrier generate-insn
    [ src>> ] keep [ slot>> ] keep [ scale>> ] keep
    [ tag>> ] keep [ temp1>> ] keep [ temp2>> ] keep drop
    %write-barrier ;


USING: accessors compiler.cfg.dce compiler.cfg.instructions ;

M: ##write-barrier live-insn? src>> live-vreg? ;


USING: accessors compiler.cfg.instructions
compiler.cfg.registers compiler.cfg.renaming kernel ;

M: ##write-barrier rename-insn-temps
    [ drop next-vreg ] change-temp1
    [ drop next-vreg ] change-temp2 drop ;


USING: accessors compiler.cfg.instructions compiler.cfg.renaming
kernel ;

M: ##write-barrier rename-insn-uses
    [ rename-value ] change-src [ rename-value ] change-slot
    drop ;


USING: compiler.cfg.gvn.rewrite compiler.cfg.gvn.slots
compiler.cfg.instructions ;

M: ##write-barrier rewrite simplify-slot-addressing ;


USING: compiler.cfg.instructions
compiler.cfg.value-numbering.rewrite
compiler.cfg.value-numbering.slots ;

M: ##write-barrier rewrite simplify-slot-addressing ;


USING: accessors compiler.cfg.instructions
compiler.cfg.ssa.construction.private kernel ;

M: ##write-barrier ssa-rename-insn-temps
    [ ] change-temp1 [ ] change-temp2 drop ;


USING: accessors compiler.cfg.instructions
compiler.cfg.ssa.construction.private kernel ;

M: ##write-barrier ssa-rename-insn-uses
    [ top-name ] change-src [ top-name ] change-slot drop ;


USING: compiler.cfg.instructions
compiler.cfg.representations.preferred cpu.architecture kernel ;

M: ##write-barrier temp-vreg-reps drop { int-rep int-rep } ;


USING: accessors arrays compiler.cfg.def-use
compiler.cfg.instructions kernel ;

M: ##write-barrier temp-vregs
    [ temp1>> ] [ temp2>> ] bi 2array ;


USING: compiler.cfg.instructions
compiler.cfg.representations.preferred cpu.architecture kernel ;

M: ##write-barrier uses-vreg-reps drop { tagged-rep int-rep } ;


USING: accessors arrays compiler.cfg.def-use
compiler.cfg.instructions kernel ;

M: ##write-barrier uses-vregs [ src>> ] [ slot>> ] bi 2array ;