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Article contents:[[toc:]] [[tags: internals]] == Entries in the compiler database The compiler database maps each user- or internal variable name to a property list holding various properties that are obtained through a previous analysis pass over the compiled code. Additionally, the database contains entries for each ''procedure-id'' (a unique internal symbol identifier) for each lambda node processed during analysis. Note that the interaction of these properties may be quite subtle and the influence certain combinations of variable and/or procedure attributes control all further optimization and translation phases. Performing modifications in the database should only be done with great care. === Variable properties ==== captured [property] captured -> <boolean> If true: variable is used outside it's home-scope and so lexically visible in an inner (nested) lambda. ==== global [property] global -> <boolean> If true: variable does not occur in any lambda-list. ==== call-sites [property] call-sites -> ((<lambda-id> <node>) ...) Known nodes of call-sites ({{##core#call}} nodes) that invoke a procedure bound to this variable. ==== home [property] home -> <lambda-id> Procedure which introduces this variable (either in the lambda-list or via {{let}}). ==== unknown [property] unknown -> <boolean> If true: variable can not have a known value. ==== assigned [property] assigned -> <boolean> If true: variable is assigned somewhere. ==== assigned-locally [property] assigned-locally -> <boolean> If true: variable has been assigned inside user lambda. ==== undefined [property] undefined -> <boolean> If true: variable is unknown yet but may be known later. {{letrec}} expands into {{let}} forms binding variables to {{##core#undefined}} and this will result in this property being set. ==== value [property] value -> <node> Variable has a known value refering to a node. ==== potential-value [property] potential-value -> <node> Global variable was assigned this value and may potentially be known. ''currently not used, I believe - fw'' ==== references [property] references -> (<node> ...) Nodes that are accesses of this variable ({{##core#variable}} nodes). ==== side-effecting [property] side-effecting -> <boolean> If true: variable names side-effecting standard-binding. ==== foldable [property] foldable -> <boolean> If true: variable names foldable standard-binding. ==== boxed [property] boxed -> <boolean> If true: variable has to be boxed after closure-conversion (i.e. is assigned to). ==== contractable [property] contractable -> <boolean> If true: variable names ''contractable'' procedure (known and called only once). A variable is contractable if it has a procedure as known value, has only one use and one call-site and if the lambda has no free non-global variables or is an internal lambda. ==== inlinable [property] inlinable -> <boolean> If true: variable names potentially inlinable procedure. ==== collapsable [property] collapsable -> <boolean> If true: variable is ''collapsable'', that is, it refers to a known constant value which is either collapsable itself or is only referenced once. ==== removable [property] removable -> <boolean> If true: variable is not used. ==== replacable [property] replacable -> <variable> Variable can be replaced by another variable. A replacable variable has a variable as known value and if either that variable has a known value itself, or if it is not captured and referenced only once, the target and the source are never assigned and the source is non-global or we are in block-mode. The target-variable is not allowed to be global. The variable that can be substituted for the current one is marked as {{replacing}}. This is done to prohibit beta-contraction of the replacing variable (It wouldn't be there, if it was contracted). Also make a variable {{replacable}}, if it has a known value of the form {{(lambda (<xvar>) (<kvar> <xvar>))}} and is an internally created procedure. ==== replacing [property] replacing -> <boolean> If true: variable can replace another variable (don't remove). ==== standard-binding [property] standard-binding -> <boolean> If true: variable names a standard binding as defined in {{c-platform.scm}}. ==== extended-binding [property] extended-binding -> <boolean> If true: variable names an extended binding as defined in {{c-platform.scm}}. ==== unused [property] unused -> <boolean> If true: variable is a formal parameter that is never used. Another way to look at it is that a variable that has a known value that is a procedure, and if the number of call-sites is equal to the number of references (does not escape), then make all formal parameters {{unused}} which are never referenced or assigned (if no rest parameter exist). Also marks the procedure as {{has-unused-parameters}} (if not in {{callback-names}}). If the procedure is internal (a continuation) do NOT mark unused parameters. ==== rest-parameter [property] rest-parameter -> #f | 'vector | 'list If true: variable holds rest-argument list mode ==== o-r/access-count [property] o-r/access-count -> <n> Contains number of references to this variable where the reference is an arguments of a ''optimizable rest operators'' (a standard operator that accesses the rest-argument and which can be replaced by a more efficient vector-operation). ==== constant [property] constant -> <boolean> If true: variable has fixed value. === Procedure properties ==== contains [property] contains -> (<lambda-id> ...) Procedures contained in this lambda. ==== contained-in [property] contained-in -> <lambda-id> Procedure containing this lambda. ==== has-unused-parameters [property] has-unused-parameters -> <boolean> If true: procedure has unused formal parameters. ==== use-expr [property] use-expr -> (<lambda-id> ...) Marks non-direct use-sites of common subexpression. ==== closure-size [property] closure-size -> <integer> Number of free variables stored in a closure. ==== customizable [property] customizable -> <boolean> If true: all call sites are known, procedure does not escape. ==== simple [property] simple -> <boolean> If true: procedure only calls its continuation and no other procedures. ==== explicit-rest [property] explicit-rest -> <boolean> A procedure that is called with consed rest list and has no unused parameter variables. ==== captured-variables [property] captured-variables -> (<var> ...) List of closed over variables. Description of your changes:

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