rust/src/comp/middle/trans/closure.rs

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import core::ctypes::c_uint;
import syntax::ast;
import syntax::ast_util;
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import lib::llvm::llvm;
import lib::llvm::{ValueRef, TypeRef};
import common::*;
import build::*;
import base::*;
import type_of::*;
import type_of::type_of; // Issue #1873
import middle::freevars::{get_freevars, freevar_info};
import back::abi;
import syntax::codemap::span;
import syntax::print::pprust::expr_to_str;
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import back::link::{
mangle_internal_name_by_path,
mangle_internal_name_by_path_and_seq};
import util::ppaux::ty_to_str;
import shape::{size_of};
import ast_map::{path, path_mod, path_name};
import driver::session::session;
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// ___Good to know (tm)__________________________________________________
//
// The layout of a closure environment in memory is
// roughly as follows:
//
// struct rust_opaque_box { // see rust_internal.h
// unsigned ref_count; // only used for fn@()
// type_desc *tydesc; // describes closure_data struct
// rust_opaque_box *prev; // (used internally by memory alloc)
// rust_opaque_box *next; // (used internally by memory alloc)
// struct closure_data {
// type_desc *bound_tdescs[]; // bound descriptors
// struct {
// upvar1_t upvar1;
// ...
// upvarN_t upvarN;
// } bound_data;
// }
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// };
//
// Note that the closure is itself a rust_opaque_box. This is true
// even for fn~ and fn&, because we wish to keep binary compatibility
// between all kinds of closures. The allocation strategy for this
// closure depends on the closure type. For a sendfn, the closure
// (and the referenced type descriptors) will be allocated in the
// exchange heap. For a fn, the closure is allocated in the task heap
// and is reference counted. For a block, the closure is allocated on
// the stack.
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//
// ## Opaque closures and the embedded type descriptor ##
//
// One interesting part of closures is that they encapsulate the data
// that they close over. So when I have a ptr to a closure, I do not
// know how many type descriptors it contains nor what upvars are
// captured within. That means I do not know precisely how big it is
// nor where its fields are located. This is called an "opaque
// closure".
//
// Typically an opaque closure suffices because we only manipulate it
// by ptr. The routine common::T_opaque_box_ptr() returns an
// appropriate type for such an opaque closure; it allows access to
// the box fields, but not the closure_data itself.
//
// But sometimes, such as when cloning or freeing a closure, we need
// to know the full information. That is where the type descriptor
// that defines the closure comes in handy. We can use its take and
// drop glue functions to allocate/free data as needed.
//
// ## Subtleties concerning alignment ##
//
// It is important that we be able to locate the closure data *without
// knowing the kind of data that is being bound*. This can be tricky
// because the alignment requirements of the bound data affects the
// alignment requires of the closure_data struct as a whole. However,
// right now this is a non-issue in any case, because the size of the
// rust_opaque_box header is always a mutiple of 16-bytes, which is
// the maximum alignment requirement we ever have to worry about.
//
// The only reason alignment matters is that, in order to learn what data
// is bound, we would normally first load the type descriptors: but their
// location is ultimately depend on their content! There is, however, a
// workaround. We can load the tydesc from the rust_opaque_box, which
// describes the closure_data struct and has self-contained derived type
// descriptors, and read the alignment from there. It's just annoying to
// do. Hopefully should this ever become an issue we'll have monomorphized
// and type descriptors will all be a bad dream.
//
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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enum environment_value {
// Evaluate expr and store result in env (used for bind).
env_expr(@ast::expr, ty::t),
// Copy the value from this llvm ValueRef into the environment.
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env_copy(ValueRef, ty::t, lval_kind),
// Move the value from this llvm ValueRef into the environment.
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env_move(ValueRef, ty::t, lval_kind),
// Access by reference (used for blocks).
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env_ref(ValueRef, ty::t, lval_kind),
}
fn ev_to_str(ccx: crate_ctxt, ev: environment_value) -> str {
alt ev {
env_expr(ex, _) { expr_to_str(ex) }
env_copy(v, t, lk) { #fmt("copy(%s,%s)", val_str(ccx.tn, v),
ty_to_str(ccx.tcx, t)) }
env_move(v, t, lk) { #fmt("move(%s,%s)", val_str(ccx.tn, v),
ty_to_str(ccx.tcx, t)) }
env_ref(v, t, lk) { #fmt("ref(%s,%s)", val_str(ccx.tn, v),
ty_to_str(ccx.tcx, t)) }
}
}
fn mk_tydesc_ty(tcx: ty::ctxt, ck: ty::closure_kind) -> ty::t {
ret alt ck {
ty::ck_block | ty::ck_box { ty::mk_type(tcx) }
ty::ck_uniq { ty::mk_send_type(tcx) }
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};
}
fn mk_tuplified_uniq_cbox_ty(tcx: ty::ctxt, cdata_ty: ty::t) -> ty::t {
let tydesc_ty = mk_tydesc_ty(tcx, ty::ck_uniq);
let cbox_ty = tuplify_cbox_ty(tcx, cdata_ty, tydesc_ty);
ret ty::mk_imm_uniq(tcx, cbox_ty);
}
// Given a closure ty, emits a corresponding tuple ty
fn mk_closure_tys(tcx: ty::ctxt,
ck: ty::closure_kind,
ty_params: [fn_ty_param],
bound_values: [environment_value])
-> (ty::t, [ty::t]) {
let bound_tys = [];
let tydesc_ty = mk_tydesc_ty(tcx, ck);
// Compute the closed over tydescs
let param_ptrs = [];
for tp in ty_params {
param_ptrs += [tydesc_ty];
option::may(tp.dicts) {|dicts|
for dict in dicts { param_ptrs += [tydesc_ty]; }
}
}
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// Compute the closed over data
for bv in bound_values {
bound_tys += [alt bv {
env_copy(_, t, _) { t }
env_move(_, t, _) { t }
env_ref(_, t, _) { t }
env_expr(_, t) { t }
}];
}
let bound_data_ty = ty::mk_tup(tcx, bound_tys);
let cdata_ty = ty::mk_tup(tcx, [ty::mk_tup(tcx, param_ptrs),
bound_data_ty]);
#debug["cdata_ty=%s", ty_to_str(tcx, cdata_ty)];
ret (cdata_ty, bound_tys);
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}
fn allocate_cbox(bcx: block,
ck: ty::closure_kind,
cdata_ty: ty::t)
-> (block, ValueRef, [ValueRef]) {
let ccx = bcx.ccx(), tcx = ccx.tcx;
fn nuke_ref_count(bcx: block, box: ValueRef) {
// Initialize ref count to arbitrary value for debugging:
let ccx = bcx.ccx();
let box = PointerCast(bcx, box, T_opaque_box_ptr(ccx));
let ref_cnt = GEPi(bcx, box, [0, abi::box_field_refcnt]);
let rc = C_int(ccx, 0x12345678);
Store(bcx, rc, ref_cnt);
}
fn store_uniq_tydesc(bcx: block,
cdata_ty: ty::t,
box: ValueRef,
&ti: option::t<@tydesc_info>) -> block {
let ccx = bcx.ccx();
let bound_tydesc = GEPi(bcx, box, [0, abi::box_field_tydesc]);
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let {bcx, val: td} = base::get_tydesc(bcx, cdata_ty, true, ti);
let td = Call(bcx, ccx.upcalls.create_shared_type_desc, [td]);
Store(bcx, td, bound_tydesc);
bcx
}
// Allocate and initialize the box:
let ti = none;
let temp_cleanups = [];
let (bcx, box) = alt ck {
ty::ck_box {
let {bcx, val: box} = trans_malloc_boxed_raw(bcx, cdata_ty, ti);
(bcx, box)
}
ty::ck_uniq {
let uniq_cbox_ty = mk_tuplified_uniq_cbox_ty(tcx, cdata_ty);
let {bcx, val: box} = uniq::alloc_uniq(bcx, uniq_cbox_ty);
nuke_ref_count(bcx, box);
let bcx = store_uniq_tydesc(bcx, cdata_ty, box, ti);
(bcx, box)
}
ty::ck_block {
let cbox_ty = tuplify_box_ty(tcx, cdata_ty);
let {bcx, val: box} = base::alloc_ty(bcx, cbox_ty);
nuke_ref_count(bcx, box);
(bcx, box)
}
};
base::lazily_emit_tydesc_glue(ccx, abi::tydesc_field_take_glue, ti);
base::lazily_emit_tydesc_glue(ccx, abi::tydesc_field_drop_glue, ti);
base::lazily_emit_tydesc_glue(ccx, abi::tydesc_field_free_glue, ti);
ret (bcx, box, temp_cleanups);
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}
type closure_result = {
llbox: ValueRef, // llvalue of ptr to closure
cdata_ty: ty::t, // type of the closure data
bcx: block // final bcx
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};
fn cast_if_we_can(bcx: block, llbox: ValueRef, t: ty::t) -> ValueRef {
let ccx = bcx.ccx();
if check type_has_static_size(ccx, t) {
let llty = type_of(ccx, t);
ret PointerCast(bcx, llbox, llty);
} else {
ret llbox;
}
}
// Given a block context and a list of tydescs and values to bind
// construct a closure out of them. If copying is true, it is a
// heap allocated closure that copies the upvars into environment.
// Otherwise, it is stack allocated and copies pointers to the upvars.
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fn store_environment(
bcx: block, lltyparams: [fn_ty_param],
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bound_values: [environment_value],
ck: ty::closure_kind)
-> closure_result {
fn maybe_clone_tydesc(bcx: block,
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ck: ty::closure_kind,
td: ValueRef) -> ValueRef {
ret alt ck {
ty::ck_block | ty::ck_box {
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td
}
ty::ck_uniq {
Call(bcx, bcx.ccx().upcalls.create_shared_type_desc, [td])
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}
};
}
let ccx = bcx.ccx(), tcx = ccx.tcx;
// compute the shape of the closure
let (cdata_ty, bound_tys) =
mk_closure_tys(tcx, ck, lltyparams, bound_values);
// allocate closure in the heap
let (bcx, llbox, temp_cleanups) =
allocate_cbox(bcx, ck, cdata_ty);
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// cbox_ty has the form of a tuple: (a, b, c) we want a ptr to a
// tuple. This could be a ptr in uniq or a box or on stack,
// whatever.
let cbox_ty = tuplify_box_ty(tcx, cdata_ty);
let cboxptr_ty = ty::mk_ptr(tcx, {ty:cbox_ty, mutbl:ast::m_imm});
let llbox = cast_if_we_can(bcx, llbox, cboxptr_ty);
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// If necessary, copy tydescs describing type parameters into the
// appropriate slot in the closure.
let {bcx:bcx, val:ty_params_slot} =
GEP_tup_like(bcx, cbox_ty, llbox,
[0, abi::box_field_body, abi::closure_body_ty_params]);
let off = 0;
for tp in lltyparams {
let cloned_td = maybe_clone_tydesc(bcx, ck, tp.desc);
Store(bcx, cloned_td, GEPi(bcx, ty_params_slot, [0, off]));
off += 1;
option::may(tp.dicts, {|dicts|
for dict in dicts {
let cast = PointerCast(bcx, dict, val_ty(cloned_td));
Store(bcx, cast, GEPi(bcx, ty_params_slot, [0, off]));
off += 1;
}
});
}
// Copy expr values into boxed bindings.
// Silly check
vec::iteri(bound_values) { |i, bv|
if (!ccx.sess.opts.no_asm_comments) {
add_comment(bcx, #fmt("Copy %s into closure",
ev_to_str(ccx, bv)));
}
let bound_data = GEP_tup_like(bcx, cbox_ty, llbox,
[0, abi::box_field_body,
abi::closure_body_bindings, i as int]);
bcx = bound_data.bcx;
let bound_data = bound_data.val;
alt bv {
env_expr(e, _) {
bcx = base::trans_expr_save_in(bcx, e, bound_data);
add_clean_temp_mem(bcx, bound_data, bound_tys[i]);
temp_cleanups += [bound_data];
}
env_copy(val, ty, owned) {
let val1 = load_if_immediate(bcx, val, ty);
bcx = base::copy_val(bcx, INIT, bound_data, val1, ty);
}
env_copy(val, ty, owned_imm) {
bcx = base::copy_val(bcx, INIT, bound_data, val, ty);
}
env_copy(_, _, temporary) {
fail "Cannot capture temporary upvar";
}
env_move(val, ty, kind) {
let src = {bcx:bcx, val:val, kind:kind};
bcx = move_val(bcx, INIT, bound_data, src, ty);
}
env_ref(val, ty, owned) {
Store(bcx, val, bound_data);
}
env_ref(val, ty, owned_imm) {
let addr = do_spill_noroot(bcx, val);
Store(bcx, addr, bound_data);
}
env_ref(_, _, temporary) {
fail "Cannot capture temporary upvar";
}
}
}
for cleanup in temp_cleanups { revoke_clean(bcx, cleanup); }
ret {llbox: llbox, cdata_ty: cdata_ty, bcx: bcx};
}
// Given a context and a list of upvars, build a closure. This just
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// collects the upvars and packages them up for store_environment.
fn build_closure(bcx0: block,
cap_vars: [capture::capture_var],
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ck: ty::closure_kind)
-> closure_result {
// If we need to, package up the iterator body to call
let env_vals = [];
let bcx = bcx0;
let tcx = bcx.tcx();
// Package up the captured upvars
vec::iter(cap_vars) { |cap_var|
let lv = trans_local_var(bcx, cap_var.def);
let nid = ast_util::def_id_of_def(cap_var.def).node;
let ty = node_id_type(bcx, nid);
alt cap_var.mode {
capture::cap_ref {
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assert ck == ty::ck_block;
ty = ty::mk_mut_ptr(tcx, ty);
env_vals += [env_ref(lv.val, ty, lv.kind)];
}
capture::cap_copy {
env_vals += [env_copy(lv.val, ty, lv.kind)];
}
capture::cap_move {
env_vals += [env_move(lv.val, ty, lv.kind)];
}
capture::cap_drop {
assert lv.kind == owned;
bcx = drop_ty(bcx, lv.val, ty);
bcx = zero_alloca(bcx, lv.val, ty);
}
}
}
ret store_environment(bcx, copy bcx.fcx.lltyparams, env_vals, ck);
}
// Given an enclosing block context, a new function context, a closure type,
// and a list of upvars, generate code to load and populate the environment
// with the upvars and type descriptors.
fn load_environment(enclosing_cx: block,
fcx: fn_ctxt,
cdata_ty: ty::t,
cap_vars: [capture::capture_var],
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ck: ty::closure_kind) {
let bcx = raw_block(fcx, fcx.llloadenv);
// Load a pointer to the closure data, skipping over the box header:
let llcdata = base::opaque_box_body(bcx, cdata_ty, fcx.llenv);
// Populate the type parameters from the environment. We need to
// do this first because the tydescs are needed to index into
// the bindings if they are dynamically sized.
let {bcx, val: lltydescs} = GEP_tup_like(bcx, cdata_ty, llcdata,
[0, abi::closure_body_ty_params]);
let off = 0;
for tp in copy enclosing_cx.fcx.lltyparams {
let tydesc = Load(bcx, GEPi(bcx, lltydescs, [0, off]));
off += 1;
let dicts = option::map(tp.dicts, {|dicts|
let rslt = [];
for dict in dicts {
let dict = Load(bcx, GEPi(bcx, lltydescs, [0, off]));
rslt += [PointerCast(bcx, dict, T_ptr(T_dict()))];
off += 1;
}
rslt
});
fcx.lltyparams += [{desc: tydesc, dicts: dicts}];
}
// Populate the upvars from the environment.
let i = 0u;
vec::iter(cap_vars) { |cap_var|
alt cap_var.mode {
capture::cap_drop { /* ignore */ }
_ {
let upvarptr =
GEP_tup_like(bcx, cdata_ty, llcdata,
[0, abi::closure_body_bindings, i as int]);
bcx = upvarptr.bcx;
let llupvarptr = upvarptr.val;
alt ck {
ty::ck_block { llupvarptr = Load(bcx, llupvarptr); }
ty::ck_uniq | ty::ck_box { }
}
let def_id = ast_util::def_id_of_def(cap_var.def);
fcx.llupvars.insert(def_id.node, llupvarptr);
i += 1u;
}
}
}
}
fn trans_expr_fn(bcx: block,
proto: ast::proto,
decl: ast::fn_decl,
body: ast::blk,
sp: span,
id: ast::node_id,
cap_clause: ast::capture_clause,
dest: dest) -> block {
if dest == ignore { ret bcx; }
let ccx = bcx.ccx(), bcx = bcx;
let fty = node_id_type(bcx, id);
let llfnty = type_of_fn_from_ty(ccx, fty, []);
let sub_path = bcx.fcx.path + [path_name("anon")];
let s = mangle_internal_name_by_path(ccx, sub_path);
let llfn = decl_internal_cdecl_fn(ccx.llmod, s, llfnty);
register_fn(ccx, sp, sub_path, "anon fn", [], id);
let trans_closure_env = fn@(ck: ty::closure_kind) -> ValueRef {
let cap_vars = capture::compute_capture_vars(
ccx.tcx, id, proto, cap_clause);
let {llbox, cdata_ty, bcx} = build_closure(bcx, cap_vars, ck);
trans_closure(ccx, sub_path, decl, body, llfn, no_self, [],
bcx.fcx.param_substs, id, {|fcx|
load_environment(bcx, fcx, cdata_ty, cap_vars, ck);
});
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llbox
};
let closure = alt proto {
ast::proto_any | ast::proto_block { trans_closure_env(ty::ck_block) }
ast::proto_box { trans_closure_env(ty::ck_box) }
ast::proto_uniq { trans_closure_env(ty::ck_uniq) }
ast::proto_bare {
trans_closure(ccx, sub_path, decl, body, llfn, no_self, [], none,
id, {|_fcx|});
C_null(T_opaque_box_ptr(ccx))
}
};
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fill_fn_pair(bcx, get_dest_addr(dest), llfn, closure);
ret bcx;
}
fn trans_bind(cx: block, f: @ast::expr, args: [option<@ast::expr>],
id: ast::node_id, dest: dest) -> block {
let f_res = trans_callee(cx, f);
ret trans_bind_1(cx, expr_ty(cx, f), f_res, args,
node_id_type(cx, id), dest);
}
fn trans_bind_1(cx: block, outgoing_fty: ty::t,
f_res: lval_maybe_callee,
args: [option<@ast::expr>], pair_ty: ty::t,
dest: dest) -> block {
let ccx = cx.ccx();
let bound: [@ast::expr] = [];
for argopt: option<@ast::expr> in args {
alt argopt { none { } some(e) { bound += [e]; } }
}
let bcx = f_res.bcx;
if dest == ignore {
for ex in bound { bcx = trans_expr(bcx, ex, ignore); }
ret bcx;
}
// Figure out which tydescs we need to pass, if any.
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let (outgoing_fty_real, lltydescs, param_bounds) = alt f_res.generic {
generic_full(ginfo) {
let tds = [], orig = 0u;
vec::iter2(ginfo.tydescs, *ginfo.param_bounds) {|td, bounds|
tds += [td];
for bound in *bounds {
alt bound {
ty::bound_iface(_) {
let dict = impl::get_dict(
bcx, option::get(ginfo.origins)[orig]);
tds += [PointerCast(bcx, dict.val, val_ty(td))];
orig += 1u;
bcx = dict.bcx;
}
_ {}
}
}
}
lazily_emit_all_generic_info_tydesc_glues(ccx, ginfo);
(ginfo.item_type, tds, ginfo.param_bounds)
}
_ { (outgoing_fty, [], @[]) }
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};
if bound.len() == 0u && lltydescs.len() == 0u &&
(f_res.env == null_env || f_res.env == is_closure) {
// Trivial 'binding': just return the closure
let lv = lval_maybe_callee_to_lval(f_res, pair_ty);
ret memmove_ty(lv.bcx, get_dest_addr(dest), lv.val, pair_ty);
}
// Arrange for the bound function to live in the first binding spot
// if the function is not statically known.
let (env_vals, target_info) = alt f_res.env {
null_env { ([], target_static(f_res.val)) }
is_closure {
// Cast the function we are binding to be the type that the
// closure will expect it to have. The type the closure knows
// about has the type parameters substituted with the real types.
let llclosurety = T_ptr(type_of(ccx, outgoing_fty));
let src_loc = PointerCast(bcx, f_res.val, llclosurety);
([env_copy(src_loc, pair_ty, owned)], target_closure)
}
self_env(slf, slf_t) {
([env_copy(slf, slf_t, owned)], target_self(f_res.val))
}
dict_env(_, _) {
ccx.sess.unimpl("binding of dynamic method calls");
}
};
// Actually construct the closure
let {llbox, cdata_ty, bcx} = store_environment(
bcx, vec::map(lltydescs, {|d| {desc: d, dicts: none}}),
env_vals + vec::map(bound, {|x| env_expr(x, expr_ty(bcx, x))}),
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ty::ck_box);
// Make thunk
let llthunk = trans_bind_thunk(
cx.fcx.ccx, cx.fcx.path, pair_ty, outgoing_fty_real, args,
cdata_ty, *param_bounds, target_info);
// Fill the function pair
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fill_fn_pair(bcx, get_dest_addr(dest), llthunk.val, llbox);
ret bcx;
}
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fn make_fn_glue(
cx: block,
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v: ValueRef,
t: ty::t,
glue_fn: fn@(block, v: ValueRef, t: ty::t) -> block)
-> block {
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let bcx = cx;
let tcx = cx.tcx();
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let fn_env = fn@(ck: ty::closure_kind) -> block {
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let box_cell_v = GEPi(cx, v, [0, abi::fn_field_box]);
let box_ptr_v = Load(cx, box_cell_v);
with_cond(cx, IsNotNull(cx, box_ptr_v)) {|bcx|
let closure_ty = ty::mk_opaque_closure_ptr(tcx, ck);
glue_fn(bcx, box_cell_v, closure_ty)
}
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};
ret alt ty::get(t).struct {
ty::ty_fn({proto: ast::proto_bare, _}) |
ty::ty_fn({proto: ast::proto_block, _}) |
ty::ty_fn({proto: ast::proto_any, _}) { bcx }
ty::ty_fn({proto: ast::proto_uniq, _}) { fn_env(ty::ck_uniq) }
ty::ty_fn({proto: ast::proto_box, _}) { fn_env(ty::ck_box) }
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_ { fail "make_fn_glue invoked on non-function type" }
};
}
fn make_opaque_cbox_take_glue(
bcx: block,
ck: ty::closure_kind,
cboxptr: ValueRef) // ptr to ptr to the opaque closure
-> block {
// Easy cases:
alt ck {
ty::ck_block { ret bcx; }
ty::ck_box { ret incr_refcnt_of_boxed(bcx, Load(bcx, cboxptr)); }
ty::ck_uniq { /* hard case: */ }
}
// Hard case, a deep copy:
let ccx = bcx.ccx(), tcx = ccx.tcx;
let llopaquecboxty = T_opaque_box_ptr(ccx);
let cbox_in = Load(bcx, cboxptr);
with_cond(bcx, IsNotNull(bcx, cbox_in)) {|bcx|
// Load the size from the type descr found in the cbox
let cbox_in = PointerCast(bcx, cbox_in, llopaquecboxty);
let tydescptr = GEPi(bcx, cbox_in, [0, abi::box_field_tydesc]);
let tydesc = Load(bcx, tydescptr);
let tydesc = PointerCast(bcx, tydesc, T_ptr(ccx.tydesc_type));
let sz = Load(bcx, GEPi(bcx, tydesc, [0, abi::tydesc_field_size]));
// Adjust sz to account for the rust_opaque_box header fields
let sz = Add(bcx, sz, shape::llsize_of(ccx, T_box_header(ccx)));
// Allocate memory, update original ptr, and copy existing data
let malloc = ccx.upcalls.shared_malloc;
let cbox_out = Call(bcx, malloc, [sz]);
let cbox_out = PointerCast(bcx, cbox_out, llopaquecboxty);
let {bcx, val: _} = call_memmove(bcx, cbox_out, cbox_in, sz);
Store(bcx, cbox_out, cboxptr);
// Take the (deeply cloned) type descriptor
let tydesc_out = GEPi(bcx, cbox_out, [0, abi::box_field_tydesc]);
let bcx = take_ty(bcx, tydesc_out, mk_tydesc_ty(tcx, ty::ck_uniq));
// Take the data in the tuple
let ti = none;
let cdata_out = GEPi(bcx, cbox_out, [0, abi::box_field_body]);
call_tydesc_glue_full(bcx, cdata_out, tydesc,
abi::tydesc_field_take_glue, ti);
bcx
}
}
fn make_opaque_cbox_drop_glue(
bcx: block,
ck: ty::closure_kind,
cboxptr: ValueRef) // ptr to the opaque closure
-> block {
alt ck {
ty::ck_block { bcx }
ty::ck_box {
decr_refcnt_maybe_free(bcx, Load(bcx, cboxptr),
ty::mk_opaque_closure_ptr(bcx.tcx(), ck))
}
ty::ck_uniq {
free_ty(bcx, Load(bcx, cboxptr),
ty::mk_opaque_closure_ptr(bcx.tcx(), ck))
}
}
}
fn make_opaque_cbox_free_glue(
bcx: block,
ck: ty::closure_kind,
cbox: ValueRef) // ptr to the opaque closure
-> block {
alt ck {
ty::ck_block { ret bcx; }
ty::ck_box | ty::ck_uniq { /* hard cases: */ }
}
let ccx = bcx.ccx(), tcx = ccx.tcx;
with_cond(bcx, IsNotNull(bcx, cbox)) {|bcx|
// Load the type descr found in the cbox
let lltydescty = T_ptr(ccx.tydesc_type);
let cbox = PointerCast(bcx, cbox, T_opaque_cbox_ptr(ccx));
let tydescptr = GEPi(bcx, cbox, [0, abi::box_field_tydesc]);
let tydesc = Load(bcx, tydescptr);
let tydesc = PointerCast(bcx, tydesc, lltydescty);
// Drop the tuple data then free the descriptor
let ti = none;
let cdata = GEPi(bcx, cbox, [0, abi::box_field_body]);
call_tydesc_glue_full(bcx, cdata, tydesc,
abi::tydesc_field_drop_glue, ti);
// Free the ty descr (if necc) and the box itself
alt ck {
ty::ck_block { fail "Impossible"; }
ty::ck_box {
trans_free(bcx, cbox)
}
ty::ck_uniq {
let bcx = free_ty(bcx, tydesc, mk_tydesc_ty(tcx, ck));
trans_shared_free(bcx, cbox)
}
}
}
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}
enum target_info {
target_closure,
target_static(ValueRef),
target_self(ValueRef),
}
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// pth is cx.path
fn trans_bind_thunk(ccx: crate_ctxt,
path: path,
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incoming_fty: ty::t,
outgoing_fty: ty::t,
args: [option<@ast::expr>],
cdata_ty: ty::t,
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param_bounds: [ty::param_bounds],
target_info: target_info)
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-> {val: ValueRef, ty: TypeRef} {
let tcx = ccx.tcx;
#debug["trans_bind_thunk[incoming_fty=%s,outgoing_fty=%s,\
cdata_ty=%s,param_bounds=%?]",
ty_to_str(tcx, incoming_fty),
ty_to_str(tcx, outgoing_fty),
ty_to_str(tcx, cdata_ty),
param_bounds];
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// Here we're not necessarily constructing a thunk in the sense of
// "function with no arguments". The result of compiling 'bind f(foo,
// bar, baz)' would be a thunk that, when called, applies f to those
// arguments and returns the result. But we're stretching the meaning of
// the word "thunk" here to also mean the result of compiling, say, 'bind
// f(foo, _, baz)', or any other bind expression that binds f and leaves
// some (or all) of the arguments unbound.
// Here, 'incoming_fty' is the type of the entire bind expression, while
// 'outgoing_fty' is the type of the function that is having some of its
// arguments bound. If f is a function that takes three arguments of type
// int and returns int, and we're translating, say, 'bind f(3, _, 5)',
// then outgoing_fty is the type of f, which is (int, int, int) -> int,
// and incoming_fty is the type of 'bind f(3, _, 5)', which is int -> int.
// Once translated, the entire bind expression will be the call f(foo,
// bar, baz) wrapped in a (so-called) thunk that takes 'bar' as its
// argument and that has bindings of 'foo' to 3 and 'baz' to 5 and a
// pointer to 'f' all saved in its environment. So, our job is to
// construct and return that thunk.
// Give the thunk a name, type, and value.
let s = mangle_internal_name_by_path_and_seq(ccx, path, "thunk");
let llthunk_ty = get_pair_fn_ty(type_of(ccx, incoming_fty));
let llthunk = decl_internal_cdecl_fn(ccx.llmod, s, llthunk_ty);
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// Create a new function context and block context for the thunk, and hold
// onto a pointer to the first block in the function for later use.
let fcx = new_fn_ctxt(ccx, path, llthunk, none);
let bcx = top_scope_block(fcx, none);
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let lltop = bcx.llbb;
// Since we might need to construct derived tydescs that depend on
// our bound tydescs, we need to load tydescs out of the environment
// before derived tydescs are constructed. To do this, we load them
// in the load_env block.
let l_bcx = raw_block(fcx, fcx.llloadenv);
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// The 'llenv' that will arrive in the thunk we're creating is an
// environment that will contain the values of its arguments and a
// pointer to the original function. This environment is always
// stored like an opaque box (see big comment at the header of the
// file), so we load the body body, which contains the type descr
// and cached data.
let llcdata = base::opaque_box_body(l_bcx, cdata_ty, fcx.llenv);
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// "target", in this context, means the function that's having some of its
// arguments bound and that will be called inside the thunk we're
// creating. (In our running example, target is the function f.) Pick
// out the pointer to the target function from the environment. The
// target function lives in the first binding spot.
let (lltargetfn, lltargetenv, starting_idx) = alt target_info {
target_static(fptr) {
(fptr, llvm::LLVMGetUndef(T_opaque_cbox_ptr(ccx)), 0)
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}
target_closure {
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let {bcx: cx, val: pair} =
GEP_tup_like(bcx, cdata_ty, llcdata,
[0, abi::closure_body_bindings, 0]);
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let lltargetenv =
Load(cx, GEPi(cx, pair, [0, abi::fn_field_box]));
let lltargetfn = Load
(cx, GEPi(cx, pair, [0, abi::fn_field_code]));
bcx = cx;
(lltargetfn, lltargetenv, 1)
}
target_self(fptr) {
let rs = GEP_tup_like(bcx, cdata_ty, llcdata,
[0, abi::closure_body_bindings, 0]);
bcx = rs.bcx;
(fptr, PointerCast(bcx, rs.val, T_opaque_cbox_ptr(ccx)), 1)
}
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};
// And then, pick out the target function's own environment. That's what
// we'll use as the environment the thunk gets.
// Get f's return type, which will also be the return type of the entire
// bind expression.
let outgoing_ret_ty = ty::ty_fn_ret(outgoing_fty);
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// Get the types of the arguments to f.
let outgoing_args = ty::ty_fn_args(outgoing_fty);
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// The 'llretptr' that will arrive in the thunk we're creating also needs
// to be the correct type. Cast it to f's return type, if necessary.
let llretptr = fcx.llretptr;
if ty::type_has_params(outgoing_ret_ty) {
let llretty = type_of(ccx, outgoing_ret_ty);
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llretptr = PointerCast(bcx, llretptr, T_ptr(llretty));
}
// Set up the three implicit arguments to the thunk.
let llargs: [ValueRef] = [llretptr, lltargetenv];
// Copy in the type parameters.
let {bcx: l_bcx, val: param_record} =
GEP_tup_like(l_bcx, cdata_ty, llcdata,
[0, abi::closure_body_ty_params]);
let off = 0;
for param in param_bounds {
let dsc = Load(l_bcx, GEPi(l_bcx, param_record, [0, off])),
dicts = none;
llargs += [dsc];
off += 1;
for bound in *param {
alt bound {
ty::bound_iface(_) {
let dict = Load(l_bcx, GEPi(l_bcx, param_record, [0, off]));
dict = PointerCast(l_bcx, dict, T_ptr(T_dict()));
llargs += [dict];
off += 1;
dicts = some(alt dicts {
none { [dict] }
some(ds) { ds + [dict] }
});
}
_ {}
}
}
fcx.lltyparams += [{desc: dsc, dicts: dicts}];
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}
let a: uint = first_tp_arg; // retptr, env come first
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let b: int = starting_idx;
let outgoing_arg_index: uint = 0u;
let llout_arg_tys: [TypeRef] =
type_of_explicit_args(ccx, outgoing_args);
for arg: option<@ast::expr> in args {
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let out_arg = outgoing_args[outgoing_arg_index];
let llout_arg_ty = llout_arg_tys[outgoing_arg_index];
alt arg {
// Arg provided at binding time; thunk copies it from
// closure.
some(e) {
let bound_arg =
GEP_tup_like(bcx, cdata_ty, llcdata,
[0, abi::closure_body_bindings, b]);
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bcx = bound_arg.bcx;
let val = bound_arg.val;
alt ty::resolved_mode(tcx, out_arg.mode) {
ast::by_val {
val = Load(bcx, val);
}
ast::by_copy {
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let {bcx: cx, val: alloc} = alloc_ty(bcx, out_arg.ty);
bcx = memmove_ty(cx, alloc, val, out_arg.ty);
bcx = take_ty(bcx, alloc, out_arg.ty);
val = alloc;
}
ast::by_ref | ast::by_mutbl_ref | ast::by_move { }
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}
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// If the type is parameterized, then we need to cast the
// type we actually have to the parameterized out type.
if ty::type_has_params(out_arg.ty) {
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val = PointerCast(bcx, val, llout_arg_ty);
}
llargs += [val];
b += 1;
}
// Arg will be provided when the thunk is invoked.
none {
let arg: ValueRef = llvm::LLVMGetParam(llthunk, a as c_uint);
if ty::type_has_params(out_arg.ty) {
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arg = PointerCast(bcx, arg, llout_arg_ty);
}
llargs += [arg];
a += 1u;
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}
}
outgoing_arg_index += 1u;
}
// Cast the outgoing function to the appropriate type.
// This is necessary because the type of the function that we have
// in the closure does not know how many type descriptors the function
// needs to take.
let lltargetty =
type_of_fn_from_ty(ccx, outgoing_fty, param_bounds);
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lltargetfn = PointerCast(bcx, lltargetfn, T_ptr(lltargetty));
Call(bcx, lltargetfn, llargs);
build_return(bcx);
finish_fn(fcx, lltop);
ret {val: llthunk, ty: llthunk_ty};
}