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Warn when inserting an implicit copy that may be expensive

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This commit is contained in:
Marijn Haverbeke 2011-09-12 13:52:12 +02:00
parent 8dd46d4384
commit bcf60c6600
2 changed files with 53 additions and 16 deletions
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65
src/comp/middle/alias.rs
View file

@ -26,6 +26,7 @@ type restrict =
@{root_var: option::t<node_id>,
node_id: node_id,
ty: ty::t,
span: span,
local_id: uint,
bindings: [node_id],
unsafe_ty: option::t<ty::t>,
@ -169,6 +170,12 @@ fn cant_copy(cx: ctx, r: restrict) -> bool {
if ty::type_allows_implicit_copy(cx.tcx, r.ty) {
r.given_up = true;
cx.copy_map.insert(r.node_id, ());
if copy_is_expensive(cx.tcx, r.ty) {
// FIXME better message
cx.tcx.sess.span_warn(r.span,
"inserting an implicit copy for type " +
util::ppaux::ty_to_str(cx.tcx, r.ty));
}
ret false;
} else { ret true; }
}
@ -201,6 +208,7 @@ fn check_call(cx: ctx, f: @ast::expr, args: [@ast::expr], sc: scope) ->
@{root_var: root_var,
node_id: arg_t.mode == ast::by_mut_ref ? 0 : arg.id,
ty: arg_t.ty,
span: arg.span,
local_id: cx.next_local,
bindings: [arg.id],
unsafe_ty: unsafe_t,
@ -282,19 +290,17 @@ fn check_alt(cx: ctx, input: @ast::expr, arms: [ast::arm], sc: scope,
let new_sc = sc;
if vec::len(dnums) > 0u {
let root_var = path_def_id(cx, root.ex);
new_sc =
@(*sc +
[
// FIXME need to use separate restrict for each binding
@{root_var: root_var,
node_id: 0,
ty: ty::mk_int(cx.tcx),
local_id: cx.next_local,
bindings: dnums,
unsafe_ty: inner_mut(root.ds),
depends_on: deps(sc, root_var),
mutable ok: valid,
mutable given_up: false}]);
// FIXME need to use separate restrict for each binding
new_sc = @(*sc + [@{root_var: root_var,
node_id: 0,
ty: ty::mk_int(cx.tcx),
span: a.pats[0].span,
local_id: cx.next_local,
bindings: dnums,
unsafe_ty: inner_mut(root.ds),
depends_on: deps(sc, root_var),
mutable ok: valid,
mutable given_up: false}]);
}
register_locals(cx, a.pats[0]);
visit::visit_arm(a, new_sc, v);
@ -332,10 +338,10 @@ fn check_for(cx: ctx, local: @ast::local, seq: @ast::expr, blk: ast::blk,
let root_var = path_def_id(cx, root.ex);
let new_sc =
@{root_var: root_var,
// FIXME reenable when trans knows how to copy for vars
node_id: 0, // blk.node.id,
ty: elt_t,
span: local.node.pat.span,
local_id: cx.next_local,
bindings: ast_util::pat_binding_ids(local.node.pat),
unsafe_ty: unsafe,
@ -516,6 +522,37 @@ fn def_is_local(d: ast::def, objfields_count: bool) -> bool {
};
}
// Heuristic, somewhat random way to decide whether to warn when inserting an
// implicit copy.
fn copy_is_expensive(tcx: ty::ctxt, ty: ty::t) -> bool {
fn score_ty(tcx: ty::ctxt, ty: ty::t) -> uint {
ret alt ty::struct(tcx, ty) {
ty::ty_nil. | ty::ty_bot. | ty::ty_bool. | ty::ty_int. |
ty::ty_uint. | ty::ty_float. | ty::ty_machine(_) |
ty::ty_char. | ty::ty_type. | ty::ty_native(_) |
ty::ty_ptr(_) { 1u }
ty::ty_box(_) { 3u }
ty::ty_constr(t, _) | ty::ty_res(_, t, _) { score_ty(tcx, t) }
ty::ty_fn(_, _, _, _, _) | ty::ty_native_fn(_, _, _) |
ty::ty_obj(_) { 4u }
ty::ty_str. | ty::ty_vec(_) { 50u }
ty::ty_uniq(t) { 1u + score_ty(tcx, t) }
ty::ty_tag(_, ts) | ty::ty_tup(ts) {
let sum = 0u;
for t in ts { sum += score_ty(tcx, t); }
sum
}
ty::ty_rec(fs) {
let sum = 0u;
for f in fs { sum += score_ty(tcx, f.mt.ty); }
sum
}
ty::ty_param(_, _) { 5u }
};
}
ret score_ty(tcx, ty) > 8u;
}
// Local Variables:
// mode: rust
// fill-column: 78;

4
src/comp/middle/trans.rs
View file

@ -2604,8 +2604,8 @@ fn build_closure(cx: @block_ctxt, upvars: @[ast::def], copying: bool) ->
closure_tys += [ty];
}
ret build_environment(cx, cx.fcx.lltydescs, closure_tys, closure_vals,
copying);
ret build_environment(cx, copy cx.fcx.lltydescs, closure_tys,
closure_vals, copying);
}
// Return a pointer to the stored typarams in a closure.