33 lines
1.4 KiB
Factor
33 lines
1.4 KiB
Factor
USING: compiler.cfg.instructions help.markup help.syntax sequences strings ;
|
|
IN: compiler.cfg.stacks.vacant
|
|
|
|
ARTICLE: "compiler.cfg.stacks.vacant" "Uninitialized/overinitialized stack location analysis"
|
|
"Consider the following sequence of instructions:"
|
|
{ $code
|
|
"##inc-d 2"
|
|
"..."
|
|
"##allot"
|
|
"##replace ... D 0"
|
|
"##replace ... D 1"
|
|
}
|
|
"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 scrub_contexts() method on vm/gc.cpp reads this information from GC maps and performs the scrubbing." ;
|
|
|
|
HELP: initial-state
|
|
{ $description "Initially the stack bottom is at 0 for both the data and retain stacks and no replaces have been registered." } ;
|
|
|
|
HELP: vacant>bit-pattern
|
|
{ $values
|
|
{ "vacant" "sequence of uninitialized stack locations" }
|
|
{ "bit-pattern" "sequence of 1:s and 0:s" }
|
|
}
|
|
{ $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 } "." }
|
|
{ $examples
|
|
{ $example
|
|
"USING: compiler.cfg.stacks.vacant prettyprint ;"
|
|
"{ 0 1 3 } vacant>bit-pattern ."
|
|
"{ 0 0 1 0 }"
|
|
}
|
|
} ;
|
|
|
|
ABOUT: "compiler.cfg.stacks.vacant"
|