rust/src/comp/middle/trans_closure.rs

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import syntax::ast;
import syntax::ast_util;
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import lib::llvm::llvm;
import llvm::{ValueRef, TypeRef};
import trans_common::*;
import trans_build::*;
import trans::*;
import middle::freevars::{get_freevars, freevar_info};
import option::{some, none};
import back::abi;
import syntax::codemap::span;
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import back::link::{
mangle_internal_name_by_path,
mangle_internal_name_by_path_and_seq};
import trans::{
trans_shared_malloc,
type_of_inner,
size_of,
node_id_type,
INIT,
trans_shared_free,
drop_ty,
new_sub_block_ctxt,
load_if_immediate,
dest
};
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// ___Good to know (tm)__________________________________________________
//
// The layout of a closure environment in memory is
// roughly as follows:
//
// struct closure_box {
// unsigned ref_count; // only used for sharid environments
// struct closure {
// type_desc *tydesc; // descriptor for the env type
// type_desc *bound_tdescs[]; // bound descriptors
// struct {
// upvar1_t upvar1;
// ...
// upvarN_t upvarN;
// } bound_data;
// };
// };
//
// NB: this struct is defined in the code in trans_common::T_closure()
// and mk_closure_ty() below. The former defines the LLVM version and
// the latter the Rust equivalent. It occurs to me that these could
// perhaps be unified, but currently they are not.
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//
// Note that the closure carries a type descriptor that describes
// itself. Trippy. This is needed because the precise types of the
// closed over data are lost in the closure type (`fn(T)->U`), so if
// we need to take/drop, we must know what data is in the upvars and
// so forth.
//
// 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. Note that in
// all cases we allocate space for a ref count just to make our lives
// easier when upcasting to block(T)->U, in the shape code, and so
// forth.
//
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tag environment_value {
// Evaluate expr and store result in env (used for bind).
env_expr(@ast::expr);
// Copy the value from this llvm ValueRef into the environment.
env_copy(ValueRef, ty::t, lval_kind);
// Move the value from this llvm ValueRef into the environment.
env_move(ValueRef, ty::t, lval_kind);
// Access by reference (used for blocks).
env_ref(ValueRef, ty::t, lval_kind);
}
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// Given a closure ty, emits a corresponding tuple ty
fn mk_closure_ty(tcx: ty::ctxt,
ck: ty::closure_kind,
n_bound_tds: uint,
bound_data_ty: ty::t)
-> ty::t {
let tydesc_ty = alt ck {
ty::closure_block. | ty::closure_shared. { ty::mk_type(tcx) }
ty::closure_send. { ty::mk_send_type(tcx) }
};
ret ty::mk_tup(tcx, [
tydesc_ty,
ty::mk_tup(tcx, vec::init_elt(tydesc_ty, n_bound_tds)),
bound_data_ty]);
}
fn shared_opaque_closure_box_ty(tcx: ty::ctxt) -> ty::t {
let opaque_closure_ty = ty::mk_opaque_closure(tcx);
ret ty::mk_imm_box(tcx, opaque_closure_ty);
}
fn send_opaque_closure_box_ty(tcx: ty::ctxt) -> ty::t {
let opaque_closure_ty = ty::mk_opaque_closure(tcx);
let tup_ty = ty::mk_tup(tcx, [ty::mk_int(tcx), opaque_closure_ty]);
ret ty::mk_uniq(tcx, {ty: tup_ty, mut: ast::imm});
}
type closure_result = {
llbox: ValueRef, // llvalue of boxed environment
box_ty: ty::t, // type of boxed environment
bcx: @block_ctxt // final bcx
};
// 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_ctxt, lltydescs: [ValueRef],
bound_values: [environment_value],
ck: ty::closure_kind)
-> closure_result {
fn dummy_environment_box(bcx: @block_ctxt, r: result)
-> (@block_ctxt, ValueRef, ValueRef) {
// Prevent glue from trying to free this.
let ccx = bcx_ccx(bcx);
let ref_cnt = GEPi(bcx, r.val, [0, abi::box_rc_field_refcnt]);
Store(r.bcx, C_int(ccx, 2), ref_cnt);
let closure = GEPi(r.bcx, r.val, [0, abi::box_rc_field_body]);
(r.bcx, closure, r.val)
}
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fn maybe_clone_tydesc(bcx: @block_ctxt,
ck: ty::closure_kind,
td: ValueRef) -> ValueRef {
ret alt ck {
ty::closure_block. | ty::closure_shared. {
td
}
ty::closure_send. {
Call(bcx, bcx_ccx(bcx).upcalls.create_shared_type_desc, [td])
}
};
}
//let ccx = bcx_ccx(bcx);
let tcx = bcx_tcx(bcx);
// First, synthesize a tuple type containing the types of all the
// bound expressions.
// bindings_ty = [bound_ty1, bound_ty2, ...]
let bound_tys = [];
for bv in bound_values {
bound_tys += [alt bv {
env_copy(_, t, _) { t }
env_move(_, t, _) { t }
env_ref(_, t, _) { t }
env_expr(e) { ty::expr_ty(tcx, e) }
}];
}
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let bound_data_ty = ty::mk_tup(tcx, bound_tys);
let closure_ty =
mk_closure_ty(tcx, ck, vec::len(lltydescs), bound_data_ty);
let temp_cleanups = [];
// Allocate a box that can hold something closure-sized.
//
// For now, no matter what kind of closure we have, we always allocate
// space for a ref cnt in the closure. If the closure is a block or
// unique closure, this ref count isn't really used: we initialize it to 2
// so that it will never drop to zero. This is a hack and could go away
// but then we'd have to modify the code to do the right thing when
// casting from a shared closure to a block.
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let (bcx, closure, box) = alt ck {
ty::closure_shared. {
let r = trans::trans_malloc_boxed(bcx, closure_ty);
add_clean_free(bcx, r.box, false);
temp_cleanups += [r.box];
(r.bcx, r.body, r.box)
}
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ty::closure_send. {
// Dummy up a box in the exchange heap.
let tup_ty = ty::mk_tup(tcx, [ty::mk_int(tcx), closure_ty]);
let box_ty = ty::mk_uniq(tcx, {ty: tup_ty, mut: ast::imm});
check trans_uniq::type_is_unique_box(bcx, box_ty);
let r = trans_uniq::alloc_uniq(bcx, box_ty);
add_clean_free(bcx, r.val, true);
temp_cleanups += [r.val];
dummy_environment_box(bcx, r)
}
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ty::closure_block. {
// Dummy up a box on the stack,
let ty = ty::mk_tup(tcx, [ty::mk_int(tcx), closure_ty]);
let r = trans::alloc_ty(bcx, ty);
dummy_environment_box(bcx, r)
}
};
// Store bindings tydesc.
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alt ck {
ty::closure_shared. | ty::closure_send. {
let bound_tydesc = GEPi(bcx, closure, [0, abi::closure_elt_tydesc]);
let ti = none;
// NDM I believe this is the correct value,
// but using it exposes bugs and limitations
// in the shape code. Therefore, I am using
// tps_normal, which is what we used before.
//
// let tps = tps_fn(vec::len(lltydescs));
let tps = tps_normal;
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let {result:closure_td, _} =
trans::get_tydesc(bcx, closure_ty, true, tps, ti);
trans::lazily_emit_tydesc_glue(bcx, abi::tydesc_field_drop_glue, ti);
trans::lazily_emit_tydesc_glue(bcx, abi::tydesc_field_free_glue, ti);
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bcx = closure_td.bcx;
let td = maybe_clone_tydesc(bcx, ck, closure_td.val);
Store(bcx, td, bound_tydesc);
}
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ty::closure_block. { /* skip this for blocks, not really relevant */ }
}
check type_is_tup_like(bcx, closure_ty);
let box_ty = ty::mk_imm_box(bcx_tcx(bcx), closure_ty);
// If necessary, copy tydescs describing type parameters into the
// appropriate slot in the closure.
let {bcx:bcx, val:ty_params_slot} =
GEP_tup_like_1(bcx, closure_ty, closure,
[0, abi::closure_elt_ty_params]);
vec::iteri(lltydescs) { |i, td|
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let ty_param_slot = GEPi(bcx, ty_params_slot, [0, i as int]);
let cloned_td = maybe_clone_tydesc(bcx, ck, td);
Store(bcx, cloned_td, ty_param_slot);
}
// Copy expr values into boxed bindings.
// Silly check
vec::iteri(bound_values) { |i, bv|
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let bound = trans::GEP_tup_like_1(bcx, box_ty, box,
[0, abi::box_rc_field_body,
abi::closure_elt_bindings,
i as int]);
bcx = bound.bcx;
alt bv {
env_expr(e) {
bcx = trans::trans_expr_save_in(bcx, e, bound.val);
add_clean_temp_mem(bcx, bound.val, bound_tys[i]);
temp_cleanups += [bound.val];
}
env_copy(val, ty, owned.) {
let val1 = load_if_immediate(bcx, val, ty);
bcx = trans::copy_val(bcx, INIT, bound.val, val1, ty);
}
env_copy(val, ty, owned_imm.) {
bcx = trans::copy_val(bcx, INIT, bound.val, 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.val, src, ty);
}
env_ref(val, ty, owned.) {
Store(bcx, val, bound.val);
}
env_ref(val, ty, owned_imm.) {
let addr = do_spill_noroot(bcx, val);
Store(bcx, addr, bound.val);
}
env_ref(_, _, temporary.) {
fail "Cannot capture temporary upvar";
}
}
}
for cleanup in temp_cleanups { revoke_clean(bcx, cleanup); }
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ret {llbox: box, box_ty: box_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_ctxt,
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(bcx);
// 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;
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let ty = ty::node_id_to_monotype(tcx, nid);
alt cap_var.mode {
capture::cap_ref. {
assert ck == ty::closure_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. {
bcx = drop_ty(bcx, lv.val, ty);
}
}
}
ret store_environment(bcx, copy bcx.fcx.lltydescs, 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.
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fn load_environment(enclosing_cx: @block_ctxt,
fcx: @fn_ctxt,
boxed_closure_ty: ty::t,
cap_vars: [capture::capture_var],
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ck: ty::closure_kind) {
let bcx = new_raw_block_ctxt(fcx, fcx.llloadenv);
let ccx = bcx_ccx(bcx);
let sp = bcx.sp;
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check (type_has_static_size(ccx, boxed_closure_ty));
let llty = type_of(ccx, sp, boxed_closure_ty);
let llclosure = PointerCast(bcx, fcx.llenv, llty);
// 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 tydesc_count = vec::len(enclosing_cx.fcx.lltydescs);
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let lltydescs = GEPi(bcx, llclosure,
[0, abi::box_rc_field_body,
abi::closure_elt_ty_params]);
uint::range(0u, tydesc_count) { |i|
let lltydescptr = GEPi(bcx, lltydescs, [0, i as int]);
fcx.lltydescs += [Load(bcx, lltydescptr)];
}
// Populate the upvars from the environment.
let path = [0, abi::box_rc_field_body, abi::closure_elt_bindings];
let i = 0u;
vec::iter(cap_vars) { |cap_var|
alt cap_var.mode {
capture::cap_drop. { /* ignore */ }
_ {
check type_is_tup_like(bcx, boxed_closure_ty);
let upvarptr = GEP_tup_like(
bcx, boxed_closure_ty, llclosure, path + [i as int]);
bcx = upvarptr.bcx;
let llupvarptr = upvarptr.val;
alt ck {
ty::closure_block. { llupvarptr = Load(bcx, llupvarptr); }
ty::closure_send. | ty::closure_shared. { }
}
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_ctxt,
decl: ast::fn_decl,
body: ast::blk,
sp: span,
id: ast::node_id,
cap_clause: ast::capture_clause,
dest: dest) -> @block_ctxt {
if dest == ignore { ret bcx; }
let ccx = bcx_ccx(bcx), bcx = bcx;
let fty = node_id_type(ccx, id);
check returns_non_ty_var(ccx, fty);
let llfnty = type_of_fn_from_ty(ccx, sp, fty, 0u);
let sub_cx = extend_path(bcx.fcx.lcx, ccx.names.next("anon"));
let s = mangle_internal_name_by_path(ccx, sub_cx.path);
let llfn = decl_internal_cdecl_fn(ccx.llmod, s, llfnty);
register_fn(ccx, sp, sub_cx.path, "anon fn", [], id);
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let trans_closure_env = lambda(ck: ty::closure_kind) -> ValueRef {
let cap_vars = capture::compute_capture_vars(
ccx.tcx, id, decl.proto, cap_clause);
let {llbox, box_ty, bcx} = build_closure(bcx, cap_vars, ck);
trans_closure(sub_cx, sp, decl, body, llfn, no_self, [], id, {|fcx|
load_environment(bcx, fcx, box_ty, cap_vars, ck);
});
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llbox
};
let closure = alt decl.proto {
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ast::proto_block. { trans_closure_env(ty::closure_block) }
ast::proto_shared(_) { trans_closure_env(ty::closure_shared) }
ast::proto_send. { trans_closure_env(ty::closure_send) }
ast::proto_bare. {
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let closure = C_null(T_opaque_boxed_closure_ptr(ccx));
trans_closure(sub_cx, sp, decl, body, llfn, no_self, [],
id, {|_fcx|});
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closure
}
};
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fill_fn_pair(bcx, get_dest_addr(dest), llfn, closure);
ret bcx;
}
fn trans_bind(cx: @block_ctxt, f: @ast::expr, args: [option::t<@ast::expr>],
id: ast::node_id, dest: dest) -> @block_ctxt {
let f_res = trans_callee(cx, f);
ret trans_bind_1(cx, ty::expr_ty(bcx_tcx(cx), f), f_res, args,
ty::node_id_to_type(bcx_tcx(cx), id), dest);
}
fn trans_bind_1(cx: @block_ctxt, outgoing_fty: ty::t,
f_res: lval_maybe_callee,
args: [option::t<@ast::expr>], pair_ty: ty::t,
dest: dest) -> @block_ctxt {
let bound: [@ast::expr] = [];
for argopt: option::t<@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.
let outgoing_fty_real; // the type with typarams still in it
let lltydescs: [ValueRef];
alt f_res.generic {
none. { outgoing_fty_real = outgoing_fty; lltydescs = []; }
some(ginfo) {
lazily_emit_all_generic_info_tydesc_glues(cx, ginfo);
outgoing_fty_real = ginfo.item_type;
lltydescs = ginfo.tydescs;
}
}
let ty_param_count = vec::len(lltydescs);
if vec::len(bound) == 0u && ty_param_count == 0u {
// Trivial 'binding': just return the closure
let lv = lval_maybe_callee_to_lval(f_res, pair_ty);
bcx = lv.bcx;
ret memmove_ty(bcx, get_dest_addr(dest), lv.val, pair_ty);
}
let closure = alt f_res.env {
null_env. { none }
_ { let (_, cl) = maybe_add_env(cx, f_res); some(cl) }
};
// FIXME: should follow from a precondition on trans_bind_1
let ccx = bcx_ccx(cx);
check (type_has_static_size(ccx, outgoing_fty));
// Arrange for the bound function to live in the first binding spot
// if the function is not statically known.
let (env_vals, target_res) = alt closure {
some(cl) {
// 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 sp = cx.sp;
let llclosurety = T_ptr(type_of(ccx, sp, outgoing_fty));
let src_loc = PointerCast(bcx, cl, llclosurety);
([env_copy(src_loc, pair_ty, owned)], none)
}
none. { ([], some(f_res.val)) }
};
// Actually construct the closure
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let {llbox, box_ty, bcx} = store_environment(
bcx, lltydescs,
env_vals + vec::map(bound, {|x| env_expr(x)}),
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ty::closure_shared);
// Make thunk
let llthunk =
trans_bind_thunk(cx.fcx.lcx, cx.sp, pair_ty, outgoing_fty_real, args,
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box_ty, ty_param_count, target_res);
// 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_ctxt,
v: ValueRef,
t: ty::t,
glue_fn: fn(@block_ctxt, v: ValueRef, t: ty::t) -> @block_ctxt)
-> @block_ctxt {
let bcx = cx;
let tcx = bcx_tcx(cx);
let fn_env = lambda(blk: block(@block_ctxt, ValueRef) -> @block_ctxt)
-> @block_ctxt {
let box_cell_v = GEPi(cx, v, [0, abi::fn_field_box]);
let box_ptr_v = Load(cx, box_cell_v);
let inner_cx = new_sub_block_ctxt(cx, "iter box");
let next_cx = new_sub_block_ctxt(cx, "next");
let null_test = IsNull(cx, box_ptr_v);
CondBr(cx, null_test, next_cx.llbb, inner_cx.llbb);
inner_cx = blk(inner_cx, box_cell_v);
Br(inner_cx, next_cx.llbb);
ret next_cx;
};
ret alt ty::struct(tcx, t) {
ty::ty_native_fn(_, _) | ty::ty_fn({proto: ast::proto_bare., _}) {
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bcx
}
ty::ty_fn({proto: ast::proto_block., _}) {
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bcx
}
ty::ty_fn({proto: ast::proto_send., _}) {
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fn_env({ |bcx, box_cell_v|
let box_ty = trans_closure::send_opaque_closure_box_ty(tcx);
glue_fn(bcx, box_cell_v, box_ty)
})
}
ty::ty_fn({proto: ast::proto_shared(_), _}) {
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fn_env({ |bcx, box_cell_v|
let box_ty = trans_closure::shared_opaque_closure_box_ty(tcx);
glue_fn(bcx, box_cell_v, box_ty)
})
}
_ { fail "make_fn_glue invoked on non-function type" }
};
}
fn call_opaque_closure_glue(bcx: @block_ctxt,
v: ValueRef, // ptr to an opaque closure
field: int) -> @block_ctxt {
let ccx = bcx_ccx(bcx);
let v = PointerCast(bcx, v, T_ptr(T_opaque_closure(ccx)));
let tydescptr = GEPi(bcx, v, [0, abi::closure_elt_tydesc]);
let tydesc = Load(bcx, tydescptr);
let ti = none;
call_tydesc_glue_full(bcx, v, tydesc, field, ti);
ret bcx;
}
// pth is cx.path
fn trans_bind_thunk(cx: @local_ctxt,
sp: span,
incoming_fty: ty::t,
outgoing_fty: ty::t,
args: [option::t<@ast::expr>],
boxed_closure_ty: ty::t,
ty_param_count: uint,
target_fn: option::t<ValueRef>)
-> {val: ValueRef, ty: TypeRef} {
// If we supported constraints on record fields, we could make the
// constraints for this function:
/*
: returns_non_ty_var(ccx, outgoing_fty),
type_has_static_size(ccx, incoming_fty) ->
*/
// but since we don't, we have to do the checks at the beginning.
let ccx = cx.ccx;
check type_has_static_size(ccx, incoming_fty);
// 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: str = mangle_internal_name_by_path_and_seq(ccx, cx.path, "thunk");
let llthunk_ty: TypeRef = get_pair_fn_ty(type_of(ccx, sp, incoming_fty));
let llthunk: ValueRef = decl_internal_cdecl_fn(ccx.llmod, s, llthunk_ty);
// 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(cx, sp, llthunk);
let bcx = new_top_block_ctxt(fcx);
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 load_env_bcx = new_raw_block_ctxt(fcx, fcx.llloadenv);
// 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. So, let's create one of those:
// The llenv pointer needs to be the correct size. That size is
// 'boxed_closure_ty', which was determined by trans_bind.
check (type_has_static_size(ccx, boxed_closure_ty));
let llclosure_ptr_ty = type_of(ccx, sp, boxed_closure_ty);
let llclosure = PointerCast(load_env_bcx, fcx.llenv, llclosure_ptr_ty);
// "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_fn {
some(fptr) {
(fptr, llvm::LLVMGetUndef(T_opaque_boxed_closure_ptr(ccx)), 0)
}
none. {
// Silly check
check type_is_tup_like(bcx, boxed_closure_ty);
let {bcx: cx, val: pair} =
GEP_tup_like(bcx, boxed_closure_ty, llclosure,
[0, abi::box_rc_field_body,
abi::closure_elt_bindings, 0]);
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)
}
};
// 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(cx.ccx.tcx, outgoing_fty);
// Get the types of the arguments to f.
let outgoing_args = ty::ty_fn_args(cx.ccx.tcx, outgoing_fty);
// 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;
let ccx = cx.ccx;
if ty::type_contains_params(ccx.tcx, outgoing_ret_ty) {
check non_ty_var(ccx, outgoing_ret_ty);
let llretty = type_of_inner(ccx, sp, outgoing_ret_ty);
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 i: uint = 0u;
while i < ty_param_count {
// Silly check
check type_is_tup_like(load_env_bcx, boxed_closure_ty);
let lltyparam_ptr =
GEP_tup_like(load_env_bcx, boxed_closure_ty, llclosure,
[0, abi::box_rc_field_body,
abi::closure_elt_ty_params, i as int]);
load_env_bcx = lltyparam_ptr.bcx;
let td = Load(load_env_bcx, lltyparam_ptr.val);
llargs += [td];
fcx.lltydescs += [td];
i += 1u;
}
let a: uint = 2u; // retptr, env come first
let b: int = starting_idx;
let outgoing_arg_index: uint = 0u;
let llout_arg_tys: [TypeRef] =
type_of_explicit_args(cx.ccx, sp, outgoing_args);
for arg: option::t<@ast::expr> in args {
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) {
// Silly check
check type_is_tup_like(bcx, boxed_closure_ty);
let bound_arg =
GEP_tup_like(bcx, boxed_closure_ty, llclosure,
[0, abi::box_rc_field_body,
abi::closure_elt_bindings, b]);
bcx = bound_arg.bcx;
let val = bound_arg.val;
if out_arg.mode == ast::by_val { val = Load(bcx, val); }
if out_arg.mode == ast::by_copy {
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;
}
// If the type is parameterized, then we need to cast the
// type we actually have to the parameterized out type.
if ty::type_contains_params(cx.ccx.tcx, out_arg.ty) {
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);
if ty::type_contains_params(cx.ccx.tcx, out_arg.ty) {
arg = PointerCast(bcx, arg, llout_arg_ty);
}
llargs += [arg];
a += 1u;
}
}
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 ccx = bcx_ccx(bcx);
check returns_non_ty_var(ccx, outgoing_fty);
let lltargetty =
type_of_fn_from_ty(ccx, sp, outgoing_fty, ty_param_count);
lltargetfn = PointerCast(bcx, lltargetfn, T_ptr(lltargetty));
Call(bcx, lltargetfn, llargs);
build_return(bcx);
finish_fn(fcx, lltop);
ret {val: llthunk, ty: llthunk_ty};
}