1 USING: compiler.cfg compiler.cfg.instructions compiler.cfg.stacks.map
2 help.markup help.syntax sequences strings ;
3 IN: compiler.cfg.stacks.vacant
5 ARTICLE: "compiler.cfg.stacks.vacant" "Uninitialized/overinitialized stack location analysis"
6 "Consider the following sequence of instructions:"
14 "The GC check runs before stack locations 0 and 1 have been initialized, and so the GC needs to scrub them so that they don't get traced. This is achieved by computing uninitialized locations with a dataflow analysis, and recording the information in GC maps. The call_frame_slot_visitor object in vm/slot_visitor.hpp reads this information from GC maps and performs the scrubbing." ;
17 { $values { "cfg" cfg } }
18 { $description "Populates the scrub-d, check-d, scrub-r and check-r slots of all gc maps in the cfg." } ;
21 { $values { "state" } { "gc-data" } }
22 { $description "Takes a stack state on the format given by " { $link trace-stack-state } " and emits an array containing two bit-patterns with locations on the data and retain stacks to scrub." } ;
26 { "vacant" "sequence of uninitialized stack locations" }
27 { "bits" "sequence of 1:s and 0:s" }
29 { $description "Converts a sequence of uninitialized stack locations to the pattern of 1:s and 0:s that can be put in the " { $slot "scrub-d" } " and " { $slot "scrub-r" } " slots of a " { $link gc-map } ". 0:s are uninitialized locations and 1:s are initialized." }
32 "USING: compiler.cfg.stacks.vacant prettyprint ;"
33 "{ 0 1 3 } vacant>bits ."
38 ABOUT: "compiler.cfg.stacks.vacant"