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some words explaining struct inst a little

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Stephen Dolan
2012-12-10 22:35:33 +00:00
parent 34ff993059
commit dcc93042d3
1 changed files with 22 additions and 8 deletions
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30
compile.c
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@@ -6,6 +6,18 @@
#include "bytecode.h"
#include "locfile.h"
/*
The intermediate representation for jq filters is as a sequence of
struct inst, which form a doubly-linked list via the next and prev
pointers.
A "block" represents a sequence of "struct inst", which may be
empty.
Blocks are generated by the parser bottom-up, so may have free
variables (refer to things not defined). See inst.bound_by and
inst.symbol.
*/
struct inst {
struct inst* next;
struct inst* prev;
@@ -22,18 +34,20 @@ struct inst {
location source;
// Binding
// An instruction requiring binding (for parameters/variables)
// An instruction requiring binding (for parameters/variables/functions)
// is in one of three states:
// bound_by = NULL - Unbound free variable
// bound_by = self - This instruction binds a variable
// bound_by = other - Uses variable bound by other instruction
// The immediate field is generally not meaningful until instructions
// are bound, and even then only for instructions which bind.
// inst->bound_by = NULL - Unbound free variable
// inst->bound_by = inst - This instruction binds a variable
// inst->bound_by = other - Uses variable bound by other instruction
// Unbound instructions (references to other things that may or may not
// exist) are created by "gen_foo_unbound", and bindings are created by
// block_bind(definition, body), which binds all instructions in
// body which are unboudn and refer to "definition" by name.
struct inst* bound_by;
char* symbol;
block subfn;
block arglist;
block subfn; // used by CLOSURE_CREATE (body of function)
block arglist; // used by CLOSURE_CREATE (formals) and CALL_JQ (arguments)
// This instruction is compiled as part of which function?
// (only used during block_compile)