1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 pub use self::ClosureKind::*;
14 use back::link::mangle_internal_name_by_path_and_seq;
16 use middle::mem_categorization::Typer;
20 use trans::cleanup::{CleanupMethods, ScopeId};
22 use trans::datum::{Datum, Lvalue, rvalue_scratch_datum};
23 use trans::datum::{Rvalue, ByValue};
26 use trans::monomorphize::{self, MonoId};
27 use trans::type_of::*;
28 use trans::type_::Type;
29 use middle::ty::{self, Ty, UnboxedClosureTyper};
30 use middle::subst::{Substs};
31 use session::config::FullDebugInfo;
32 use util::ppaux::ty_to_string;
37 // ___Good to know (tm)__________________________________________________
39 // The layout of a closure environment in memory is
40 // roughly as follows:
42 // struct rust_opaque_box { // see rust_internal.h
43 // unsigned ref_count; // obsolete (part of @T's header)
44 // fn(void*) *drop_glue; // destructor (for proc)
45 // rust_opaque_box *prev; // obsolete (part of @T's header)
46 // rust_opaque_box *next; // obsolete (part of @T's header)
47 // struct closure_data {
54 // Note that the closure is itself a rust_opaque_box. This is true
55 // even for ~fn and ||, because we wish to keep binary compatibility
56 // between all kinds of closures. The allocation strategy for this
57 // closure depends on the closure type. For a sendfn, the closure
58 // (and the referenced type descriptors) will be allocated in the
59 // exchange heap. For a fn, the closure is allocated in the task heap
60 // and is reference counted. For a block, the closure is allocated on
63 // ## Opaque closures and the embedded type descriptor ##
65 // One interesting part of closures is that they encapsulate the data
66 // that they close over. So when I have a ptr to a closure, I do not
67 // know how many type descriptors it contains nor what upvars are
68 // captured within. That means I do not know precisely how big it is
69 // nor where its fields are located. This is called an "opaque
72 // Typically an opaque closure suffices because we only manipulate it
73 // by ptr. The routine Type::at_box().ptr_to() returns an appropriate
74 // type for such an opaque closure; it allows access to the box fields,
75 // but not the closure_data itself.
77 // But sometimes, such as when cloning or freeing a closure, we need
78 // to know the full information. That is where the type descriptor
79 // that defines the closure comes in handy. We can use its take and
80 // drop glue functions to allocate/free data as needed.
82 // ## Subtleties concerning alignment ##
84 // It is important that we be able to locate the closure data *without
85 // knowing the kind of data that is being bound*. This can be tricky
86 // because the alignment requirements of the bound data affects the
87 // alignment requires of the closure_data struct as a whole. However,
88 // right now this is a non-issue in any case, because the size of the
89 // rust_opaque_box header is always a multiple of 16-bytes, which is
90 // the maximum alignment requirement we ever have to worry about.
92 // The only reason alignment matters is that, in order to learn what data
93 // is bound, we would normally first load the type descriptors: but their
94 // location is ultimately depend on their content! There is, however, a
95 // workaround. We can load the tydesc from the rust_opaque_box, which
96 // describes the closure_data struct and has self-contained derived type
97 // descriptors, and read the alignment from there. It's just annoying to
98 // do. Hopefully should this ever become an issue we'll have monomorphized
99 // and type descriptors will all be a bad dream.
101 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
104 pub struct EnvValue<'tcx> {
105 action: ast::CaptureClause,
106 datum: Datum<'tcx, Lvalue>
109 impl<'tcx> EnvValue<'tcx> {
110 pub fn to_string<'a>(&self, ccx: &CrateContext<'a, 'tcx>) -> String {
111 format!("{:?}({})", self.action, self.datum.to_string(ccx))
115 // Given a closure ty, emits a corresponding tuple ty
116 pub fn mk_closure_tys<'tcx>(tcx: &ty::ctxt<'tcx>,
117 bound_values: &[EnvValue<'tcx>])
119 // determine the types of the values in the env. Note that this
120 // is the actual types that will be stored in the map, not the
121 // logical types as the user sees them, so by-ref upvars must be
122 // converted to ptrs.
123 let bound_tys = bound_values.iter().map(|bv| {
125 ast::CaptureByValue => bv.datum.ty,
126 ast::CaptureByRef => ty::mk_mut_ptr(tcx, bv.datum.ty)
129 let cdata_ty = ty::mk_tup(tcx, bound_tys);
130 debug!("cdata_ty={}", ty_to_string(tcx, cdata_ty));
134 fn tuplify_box_ty<'tcx>(tcx: &ty::ctxt<'tcx>, t: Ty<'tcx>) -> Ty<'tcx> {
135 let ptr = ty::mk_imm_ptr(tcx, tcx.types.i8);
136 ty::mk_tup(tcx, vec!(tcx.types.uint, ty::mk_nil_ptr(tcx), ptr, ptr, t))
139 pub struct ClosureResult<'blk, 'tcx: 'blk> {
140 llbox: ValueRef, // llvalue of ptr to closure
141 cdata_ty: Ty<'tcx>, // type of the closure data
142 bcx: Block<'blk, 'tcx> // final bcx
145 // Given a block context and a list of tydescs and values to bind
146 // construct a closure out of them. If copying is true, it is a
147 // heap allocated closure that copies the upvars into environment.
148 // Otherwise, it is stack allocated and copies pointers to the upvars.
149 pub fn store_environment<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
150 bound_values: Vec<EnvValue<'tcx>>)
151 -> ClosureResult<'blk, 'tcx> {
152 let _icx = push_ctxt("closure::store_environment");
156 // compute the type of the closure
157 let cdata_ty = mk_closure_tys(tcx, &bound_values[]);
159 // cbox_ty has the form of a tuple: (a, b, c) we want a ptr to a
160 // tuple. This could be a ptr in uniq or a box or on stack,
162 let cbox_ty = tuplify_box_ty(tcx, cdata_ty);
163 let cboxptr_ty = ty::mk_ptr(tcx, ty::mt {ty:cbox_ty, mutbl:ast::MutImmutable});
164 let llboxptr_ty = type_of(ccx, cboxptr_ty);
166 // If there are no bound values, no point in allocating anything.
167 if bound_values.is_empty() {
168 return ClosureResult {llbox: C_null(llboxptr_ty),
173 // allocate closure in the heap
174 let llbox = alloc_ty(bcx, cbox_ty, "__closure");
176 let llbox = PointerCast(bcx, llbox, llboxptr_ty);
177 debug!("tuplify_box_ty = {}", ty_to_string(tcx, cbox_ty));
179 // Copy expr values into boxed bindings.
181 for (i, bv) in bound_values.into_iter().enumerate() {
182 debug!("Copy {} into closure", bv.to_string(ccx));
184 if ccx.sess().asm_comments() {
185 add_comment(bcx, &format!("Copy {} into closure",
186 bv.to_string(ccx))[]);
189 let bound_data = GEPi(bcx, llbox, &[0u, abi::BOX_FIELD_BODY, i]);
192 ast::CaptureByValue => {
193 bcx = bv.datum.store_to(bcx, bound_data);
195 ast::CaptureByRef => {
196 Store(bcx, bv.datum.to_llref(), bound_data);
201 ClosureResult { llbox: llbox, cdata_ty: cdata_ty, bcx: bcx }
204 // Given a context and a list of upvars, build a closure. This just
205 // collects the upvars and packages them up for store_environment.
206 fn build_closure<'blk, 'tcx>(bcx0: Block<'blk, 'tcx>,
207 freevar_mode: ast::CaptureClause,
208 freevars: &Vec<ty::Freevar>)
209 -> ClosureResult<'blk, 'tcx> {
210 let _icx = push_ctxt("closure::build_closure");
212 // If we need to, package up the iterator body to call
215 // Package up the captured upvars
216 let mut env_vals = Vec::new();
217 for freevar in freevars.iter() {
218 let datum = expr::trans_local_var(bcx, freevar.def);
219 env_vals.push(EnvValue {action: freevar_mode, datum: datum});
222 store_environment(bcx, env_vals)
225 // Given an enclosing block context, a new function context, a closure type,
226 // and a list of upvars, generate code to load and populate the environment
227 // with the upvars and type descriptors.
228 fn load_environment<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
230 freevars: &[ty::Freevar],
231 store: ty::TraitStore)
232 -> Block<'blk, 'tcx> {
233 let _icx = push_ctxt("closure::load_environment");
235 // Load a pointer to the closure data, skipping over the box header:
236 let llcdata = at_box_body(bcx, cdata_ty, bcx.fcx.llenv.unwrap());
238 // Store the pointer to closure data in an alloca for debug info because that's what the
239 // llvm.dbg.declare intrinsic expects
240 let env_pointer_alloca = if bcx.sess().opts.debuginfo == FullDebugInfo {
241 let alloc = alloc_ty(bcx, ty::mk_mut_ptr(bcx.tcx(), cdata_ty), "__debuginfo_env_ptr");
242 Store(bcx, llcdata, alloc);
248 // Populate the upvars from the environment
250 for freevar in freevars.iter() {
251 let mut upvarptr = GEPi(bcx, llcdata, &[0u, i]);
252 let captured_by_ref = match store {
253 ty::RegionTraitStore(..) => {
254 upvarptr = Load(bcx, upvarptr);
257 ty::UniqTraitStore => false
259 let def_id = freevar.def.def_id();
261 bcx.fcx.llupvars.borrow_mut().insert(def_id.node, upvarptr);
262 if let Some(env_pointer_alloca) = env_pointer_alloca {
263 debuginfo::create_captured_var_metadata(
278 fn load_unboxed_closure_environment<'blk, 'tcx>(
279 bcx: Block<'blk, 'tcx>,
280 arg_scope_id: ScopeId,
281 freevar_mode: ast::CaptureClause,
282 freevars: &[ty::Freevar])
283 -> Block<'blk, 'tcx> {
284 let _icx = push_ctxt("closure::load_environment");
286 // Special case for small by-value selfs.
287 let closure_id = ast_util::local_def(bcx.fcx.id);
288 let self_type = self_type_for_unboxed_closure(bcx.ccx(), closure_id,
289 node_id_type(bcx, closure_id.node));
290 let kind = kind_for_unboxed_closure(bcx.ccx(), closure_id);
291 let llenv = if kind == ty::FnOnceUnboxedClosureKind &&
292 !arg_is_indirect(bcx.ccx(), self_type) {
293 let datum = rvalue_scratch_datum(bcx,
295 "unboxed_closure_env");
296 store_ty(bcx, bcx.fcx.llenv.unwrap(), datum.val, self_type);
299 bcx.fcx.llenv.unwrap()
302 // Store the pointer to closure data in an alloca for debug info because that's what the
303 // llvm.dbg.declare intrinsic expects
304 let env_pointer_alloca = if bcx.sess().opts.debuginfo == FullDebugInfo {
305 let alloc = alloca(bcx, val_ty(llenv), "__debuginfo_env_ptr");
306 Store(bcx, llenv, alloc);
312 for (i, freevar) in freevars.iter().enumerate() {
313 let mut upvar_ptr = GEPi(bcx, llenv, &[0, i]);
314 let captured_by_ref = match freevar_mode {
315 ast::CaptureByRef => {
316 upvar_ptr = Load(bcx, upvar_ptr);
319 ast::CaptureByValue => false
321 let def_id = freevar.def.def_id();
322 bcx.fcx.llupvars.borrow_mut().insert(def_id.node, upvar_ptr);
324 if kind == ty::FnOnceUnboxedClosureKind && freevar_mode == ast::CaptureByValue {
325 bcx.fcx.schedule_drop_mem(arg_scope_id,
327 node_id_type(bcx, def_id.node))
330 if let Some(env_pointer_alloca) = env_pointer_alloca {
331 debuginfo::create_captured_var_metadata(
344 fn fill_fn_pair(bcx: Block, pair: ValueRef, llfn: ValueRef, llenvptr: ValueRef) {
345 Store(bcx, llfn, GEPi(bcx, pair, &[0u, abi::FAT_PTR_ADDR]));
346 let llenvptr = PointerCast(bcx, llenvptr, Type::i8p(bcx.ccx()));
347 Store(bcx, llenvptr, GEPi(bcx, pair, &[0u, abi::FAT_PTR_EXTRA]));
351 pub enum ClosureKind<'tcx> {
353 // See load_environment.
354 BoxedClosure(Ty<'tcx>, ty::TraitStore),
355 // See load_unboxed_closure_environment.
356 UnboxedClosure(ast::CaptureClause)
359 pub struct ClosureEnv<'a, 'tcx> {
360 freevars: &'a [ty::Freevar],
361 pub kind: ClosureKind<'tcx>
364 impl<'a, 'tcx> ClosureEnv<'a, 'tcx> {
365 pub fn new(freevars: &'a [ty::Freevar], kind: ClosureKind<'tcx>)
366 -> ClosureEnv<'a, 'tcx> {
373 pub fn load<'blk>(self, bcx: Block<'blk, 'tcx>, arg_scope: ScopeId)
374 -> Block<'blk, 'tcx> {
375 // Don't bother to create the block if there's nothing to load
376 if self.freevars.is_empty() {
382 BoxedClosure(cdata_ty, store) => {
383 load_environment(bcx, cdata_ty, self.freevars, store)
385 UnboxedClosure(freevar_mode) => {
386 load_unboxed_closure_environment(bcx, arg_scope, freevar_mode, self.freevars)
392 /// Translates the body of a closure expression.
397 /// - `id`: The id of the closure expression.
398 /// - `cap_clause`: information about captured variables, if any.
399 /// - `dest`: where to write the closure value, which must be a
400 /// (fn ptr, env) pair
401 pub fn trans_expr_fn<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
402 store: ty::TraitStore,
407 -> Block<'blk, 'tcx> {
408 let _icx = push_ctxt("closure::trans_expr_fn");
410 let dest_addr = match dest {
411 expr::SaveIn(p) => p,
413 return bcx; // closure construction is non-side-effecting
419 let fty = node_id_type(bcx, id);
420 let s = tcx.map.with_path(id, |path| {
421 mangle_internal_name_by_path_and_seq(path, "closure")
423 let llfn = decl_internal_rust_fn(ccx, fty, &s[]);
425 // set an inline hint for all closures
426 set_inline_hint(llfn);
428 let freevar_mode = tcx.capture_mode(id);
429 let freevars: Vec<ty::Freevar> =
430 ty::with_freevars(tcx, id, |fv| fv.iter().map(|&fv| fv).collect());
436 } = build_closure(bcx, freevar_mode, &freevars);
442 bcx.fcx.param_substs,
445 ty::erase_late_bound_regions(ccx.tcx(), &ty::ty_fn_ret(fty)),
447 ClosureEnv::new(&freevars[],
448 BoxedClosure(cdata_ty, store)));
449 fill_fn_pair(bcx, dest_addr, llfn, llbox);
453 /// Returns the LLVM function declaration for an unboxed closure, creating it
454 /// if necessary. If the ID does not correspond to a closure ID, returns None.
455 pub fn get_or_create_declaration_if_unboxed_closure<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
456 closure_id: ast::DefId,
457 substs: &Substs<'tcx>)
458 -> Option<Datum<'tcx, Rvalue>> {
459 if !ccx.tcx().unboxed_closures.borrow().contains_key(&closure_id) {
460 // Not an unboxed closure.
464 let function_type = ty::node_id_to_type(ccx.tcx(), closure_id.node);
465 let function_type = monomorphize::apply_param_substs(ccx.tcx(), substs, &function_type);
467 // Normalize type so differences in regions and typedefs don't cause
468 // duplicate declarations
469 let function_type = erase_regions(ccx.tcx(), &function_type);
470 let params = match function_type.sty {
471 ty::ty_unboxed_closure(_, _, ref substs) => substs.types.clone(),
474 let mono_id = MonoId {
479 match ccx.unboxed_closure_vals().borrow().get(&mono_id) {
481 debug!("get_or_create_declaration_if_unboxed_closure(): found \
483 return Some(Datum::new(llfn, function_type, Rvalue::new(ByValue)))
488 let symbol = ccx.tcx().map.with_path(closure_id.node, |path| {
489 mangle_internal_name_by_path_and_seq(path, "unboxed_closure")
492 let llfn = decl_internal_rust_fn(ccx, function_type, &symbol[]);
494 // set an inline hint for all closures
495 set_inline_hint(llfn);
497 debug!("get_or_create_declaration_if_unboxed_closure(): inserting new \
498 closure {:?} (type {})",
500 ccx.tn().type_to_string(val_ty(llfn)));
501 ccx.unboxed_closure_vals().borrow_mut().insert(mono_id, llfn);
503 Some(Datum::new(llfn, function_type, Rvalue::new(ByValue)))
506 pub fn trans_unboxed_closure<'blk, 'tcx>(
507 mut bcx: Block<'blk, 'tcx>,
514 let _icx = push_ctxt("closure::trans_unboxed_closure");
516 debug!("trans_unboxed_closure()");
518 let closure_id = ast_util::local_def(id);
519 let llfn = get_or_create_declaration_if_unboxed_closure(
522 bcx.fcx.param_substs).unwrap();
524 // Get the type of this closure. Use the current `param_substs` as
525 // the closure substitutions. This makes sense because the closure
526 // takes the same set of type arguments as the enclosing fn, and
527 // this function (`trans_unboxed_closure`) is invoked at the point
528 // of the closure expression.
529 let typer = NormalizingUnboxedClosureTyper::new(bcx.tcx());
530 let function_type = typer.unboxed_closure_type(closure_id, bcx.fcx.param_substs);
532 let freevars: Vec<ty::Freevar> =
533 ty::with_freevars(bcx.tcx(), id, |fv| fv.iter().map(|&fv| fv).collect());
534 let freevar_mode = bcx.tcx().capture_mode(id);
536 let sig = ty::erase_late_bound_regions(bcx.tcx(), &function_type.sig);
538 trans_closure(bcx.ccx(),
542 bcx.fcx.param_substs,
547 ClosureEnv::new(&freevars[],
548 UnboxedClosure(freevar_mode)));
550 // Don't hoist this to the top of the function. It's perfectly legitimate
551 // to have a zero-size unboxed closure (in which case dest will be
552 // `Ignore`) and we must still generate the closure body.
553 let dest_addr = match dest {
554 expr::SaveIn(p) => p,
556 debug!("trans_unboxed_closure() ignoring result");
561 let repr = adt::represent_type(bcx.ccx(), node_id_type(bcx, id));
563 // Create the closure.
564 for (i, freevar) in freevars.iter().enumerate() {
565 let datum = expr::trans_local_var(bcx, freevar.def);
566 let upvar_slot_dest = adt::trans_field_ptr(bcx,
572 ast::CaptureByValue => {
573 bcx = datum.store_to(bcx, upvar_slot_dest);
575 ast::CaptureByRef => {
576 Store(bcx, datum.to_llref(), upvar_slot_dest);
580 adt::trans_set_discr(bcx, &*repr, dest_addr, 0);