141 lines
4.6 KiB
Rust
141 lines
4.6 KiB
Rust
// A pass that annotates for each loops and functions with the free
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// variables that they contain.
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import std::map;
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import std::map::*;
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import std::option;
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import std::int;
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import std::istr;
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import std::option::*;
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import syntax::ast;
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import syntax::ast_util;
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import syntax::visit;
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import driver::session;
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import middle::resolve;
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import syntax::codemap::span;
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export annotate_freevars;
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export freevar_map;
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export get_freevars;
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export has_freevars;
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// A vector of defs representing the free variables referred to in a function.
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// (The def_upvar will already have been stripped).
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type freevar_info = @[ast::def];
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type freevar_map = hashmap<ast::node_id, freevar_info>;
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// Searches through part of the AST for all references to locals or
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// upvars in this frame and returns the list of definition IDs thus found.
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// Since we want to be able to collect upvars in some arbitrary piece
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// of the AST, we take a walker function that we invoke with a visitor
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// in order to start the search.
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fn collect_freevars(def_map: &resolve::def_map,
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walker: &fn(&visit::vt<int>)) -> freevar_info {
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let seen = new_int_hash();
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let refs = @mutable [];
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fn ignore_item(_i: &@ast::item, _depth: &int, _v: &visit::vt<int>) {}
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let walk_expr = lambda(expr: &@ast::expr, depth: &int,
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v: &visit::vt<int>) {
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alt expr.node {
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ast::expr_fn(f) {
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if f.proto == ast::proto_block ||
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f.proto == ast::proto_closure {
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visit::visit_expr(expr, depth + 1, v);
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}
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}
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ast::expr_for_each(dcl, x, b) {
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v.visit_local(dcl, depth, v);
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v.visit_expr(x, depth, v);
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v.visit_block(b, depth + 1, v);
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}
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ast::expr_path(path) {
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let def = def_map.get(expr.id), i = 0;
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while i < depth {
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alt {def} {
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ast::def_upvar(_, inner, _) {
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def = *inner;
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}
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_ { break; }
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}
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i += 1;
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}
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if i == depth { // Made it to end of loop
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let dnum = ast_util::def_id_of_def(def).node;
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if !seen.contains_key(dnum) {
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*refs += [def];
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seen.insert(dnum, ());
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}
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}
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}
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_ { visit::visit_expr(expr, depth, v); }
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}
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};
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walker(visit::mk_vt(@{visit_item: ignore_item,
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visit_expr: walk_expr
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with *visit::default_visitor()}));
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ret @*refs;
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}
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// Build a map from every function and for-each body to a set of the
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// freevars contained in it. The implementation is not particularly
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// efficient as it fully recomputes the free variables at every
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// node of interest rather than building up the free variables in
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// one pass. This could be improved upon if it turns out to matter.
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fn annotate_freevars(def_map: &resolve::def_map,
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crate: &@ast::crate) -> freevar_map {
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let freevars = new_int_hash();
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let walk_fn = lambda (f: &ast::_fn, tps: &[ast::ty_param], sp: &span,
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i: &ast::fn_ident, nid: ast::node_id) {
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let start_walk = lambda (v: &visit::vt<int>) {
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v.visit_fn(f, tps, sp, i, nid, 1, v);
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};
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let vars = collect_freevars(def_map, start_walk);
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freevars.insert(nid, vars);
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};
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let walk_expr = lambda (expr: &@ast::expr) {
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alt expr.node {
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ast::expr_for_each(local, _, body) {
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let start_walk = lambda (v: &visit::vt<int>) {
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v.visit_block(body, 1, v);
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};
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let vars = collect_freevars(def_map, start_walk);
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freevars.insert(body.node.id, vars);
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}
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_ { }
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}
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};
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let visitor =
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visit::mk_simple_visitor(@{visit_fn: walk_fn, visit_expr: walk_expr
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with *visit::default_simple_visitor()});
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visit::visit_crate(*crate, (), visitor);
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ret freevars;
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}
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fn get_freevars(tcx: &ty::ctxt, fid: ast::node_id) -> freevar_info {
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alt tcx.freevars.find(fid) {
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none. {
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fail ~"get_freevars: " + int::str(fid)
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+ ~" has no freevars";
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}
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some(d) { ret d; }
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}
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}
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fn has_freevars(tcx: &ty::ctxt, fid: ast::node_id) -> bool {
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ret std::vec::len(*get_freevars(tcx, fid)) != 0u;
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}
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// Local Variables:
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// mode: rust
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// fill-column: 78;
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// indent-tabs-mode: nil
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// c-basic-offset: 4
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// buffer-file-coding-system: utf-8-unix
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// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
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// End:
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