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, DatumBlock, Expr, 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::Repr;
33 use util::ppaux::ty_to_string;
35 use arena::TypedArena;
39 // ___Good to know (tm)__________________________________________________
41 // The layout of a closure environment in memory is
42 // roughly as follows:
44 // struct rust_opaque_box { // see rust_internal.h
45 // unsigned ref_count; // obsolete (part of @T's header)
46 // fn(void*) *drop_glue; // destructor (for proc)
47 // rust_opaque_box *prev; // obsolete (part of @T's header)
48 // rust_opaque_box *next; // obsolete (part of @T's header)
49 // struct closure_data {
56 // Note that the closure is itself a rust_opaque_box. This is true
57 // even for ~fn and ||, because we wish to keep binary compatibility
58 // between all kinds of closures. The allocation strategy for this
59 // closure depends on the closure type. For a sendfn, the closure
60 // (and the referenced type descriptors) will be allocated in the
61 // exchange heap. For a fn, the closure is allocated in the task heap
62 // and is reference counted. For a block, the closure is allocated on
65 // ## Opaque closures and the embedded type descriptor ##
67 // One interesting part of closures is that they encapsulate the data
68 // that they close over. So when I have a ptr to a closure, I do not
69 // know how many type descriptors it contains nor what upvars are
70 // captured within. That means I do not know precisely how big it is
71 // nor where its fields are located. This is called an "opaque
74 // Typically an opaque closure suffices because we only manipulate it
75 // by ptr. The routine Type::at_box().ptr_to() returns an appropriate
76 // type for such an opaque closure; it allows access to the box fields,
77 // but not the closure_data itself.
79 // But sometimes, such as when cloning or freeing a closure, we need
80 // to know the full information. That is where the type descriptor
81 // that defines the closure comes in handy. We can use its take and
82 // drop glue functions to allocate/free data as needed.
84 // ## Subtleties concerning alignment ##
86 // It is important that we be able to locate the closure data *without
87 // knowing the kind of data that is being bound*. This can be tricky
88 // because the alignment requirements of the bound data affects the
89 // alignment requires of the closure_data struct as a whole. However,
90 // right now this is a non-issue in any case, because the size of the
91 // rust_opaque_box header is always a multiple of 16-bytes, which is
92 // the maximum alignment requirement we ever have to worry about.
94 // The only reason alignment matters is that, in order to learn what data
95 // is bound, we would normally first load the type descriptors: but their
96 // location is ultimately depend on their content! There is, however, a
97 // workaround. We can load the tydesc from the rust_opaque_box, which
98 // describes the closure_data struct and has self-contained derived type
99 // descriptors, and read the alignment from there. It's just annoying to
100 // do. Hopefully should this ever become an issue we'll have monomorphized
101 // and type descriptors will all be a bad dream.
103 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
106 pub struct EnvValue<'tcx> {
107 action: ast::CaptureClause,
108 datum: Datum<'tcx, Lvalue>
111 impl<'tcx> EnvValue<'tcx> {
112 pub fn to_string<'a>(&self, ccx: &CrateContext<'a, 'tcx>) -> String {
113 format!("{}({})", self.action, self.datum.to_string(ccx))
117 // Given a closure ty, emits a corresponding tuple ty
118 pub fn mk_closure_tys<'tcx>(tcx: &ty::ctxt<'tcx>,
119 bound_values: &[EnvValue<'tcx>])
121 // determine the types of the values in the env. Note that this
122 // is the actual types that will be stored in the map, not the
123 // logical types as the user sees them, so by-ref upvars must be
124 // converted to ptrs.
125 let bound_tys = bound_values.iter().map(|bv| {
127 ast::CaptureByValue => bv.datum.ty,
128 ast::CaptureByRef => ty::mk_mut_ptr(tcx, bv.datum.ty)
131 let cdata_ty = ty::mk_tup(tcx, bound_tys);
132 debug!("cdata_ty={}", ty_to_string(tcx, cdata_ty));
136 fn tuplify_box_ty<'tcx>(tcx: &ty::ctxt<'tcx>, t: Ty<'tcx>) -> Ty<'tcx> {
137 let ptr = ty::mk_imm_ptr(tcx, tcx.types.i8);
138 ty::mk_tup(tcx, vec!(tcx.types.uint, ty::mk_nil_ptr(tcx), ptr, ptr, t))
141 pub struct ClosureResult<'blk, 'tcx: 'blk> {
142 llbox: ValueRef, // llvalue of ptr to closure
143 cdata_ty: Ty<'tcx>, // type of the closure data
144 bcx: Block<'blk, 'tcx> // final bcx
147 // Given a block context and a list of tydescs and values to bind
148 // construct a closure out of them. If copying is true, it is a
149 // heap allocated closure that copies the upvars into environment.
150 // Otherwise, it is stack allocated and copies pointers to the upvars.
151 pub fn store_environment<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
152 bound_values: Vec<EnvValue<'tcx>>)
153 -> ClosureResult<'blk, 'tcx> {
154 let _icx = push_ctxt("closure::store_environment");
158 // compute the type of the closure
159 let cdata_ty = mk_closure_tys(tcx, bound_values[]);
161 // cbox_ty has the form of a tuple: (a, b, c) we want a ptr to a
162 // tuple. This could be a ptr in uniq or a box or on stack,
164 let cbox_ty = tuplify_box_ty(tcx, cdata_ty);
165 let cboxptr_ty = ty::mk_ptr(tcx, ty::mt {ty:cbox_ty, mutbl:ast::MutImmutable});
166 let llboxptr_ty = type_of(ccx, cboxptr_ty);
168 // If there are no bound values, no point in allocating anything.
169 if bound_values.is_empty() {
170 return ClosureResult {llbox: C_null(llboxptr_ty),
175 // allocate closure in the heap
176 let llbox = alloc_ty(bcx, cbox_ty, "__closure");
178 let llbox = PointerCast(bcx, llbox, llboxptr_ty);
179 debug!("tuplify_box_ty = {}", ty_to_string(tcx, cbox_ty));
181 // Copy expr values into boxed bindings.
183 for (i, bv) in bound_values.into_iter().enumerate() {
184 debug!("Copy {} into closure", bv.to_string(ccx));
186 if ccx.sess().asm_comments() {
187 add_comment(bcx, format!("Copy {} into closure",
188 bv.to_string(ccx))[]);
191 let bound_data = GEPi(bcx, llbox, &[0u, abi::BOX_FIELD_BODY, i]);
194 ast::CaptureByValue => {
195 bcx = bv.datum.store_to(bcx, bound_data);
197 ast::CaptureByRef => {
198 Store(bcx, bv.datum.to_llref(), bound_data);
203 ClosureResult { llbox: llbox, cdata_ty: cdata_ty, bcx: bcx }
206 // Given a context and a list of upvars, build a closure. This just
207 // collects the upvars and packages them up for store_environment.
208 fn build_closure<'blk, 'tcx>(bcx0: Block<'blk, 'tcx>,
209 freevar_mode: ast::CaptureClause,
210 freevars: &Vec<ty::Freevar>)
211 -> ClosureResult<'blk, 'tcx> {
212 let _icx = push_ctxt("closure::build_closure");
214 // If we need to, package up the iterator body to call
217 // Package up the captured upvars
218 let mut env_vals = Vec::new();
219 for freevar in freevars.iter() {
220 let datum = expr::trans_local_var(bcx, freevar.def);
221 env_vals.push(EnvValue {action: freevar_mode, datum: datum});
224 store_environment(bcx, env_vals)
227 // Given an enclosing block context, a new function context, a closure type,
228 // and a list of upvars, generate code to load and populate the environment
229 // with the upvars and type descriptors.
230 fn load_environment<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
232 freevars: &[ty::Freevar],
233 store: ty::TraitStore)
234 -> Block<'blk, 'tcx> {
235 let _icx = push_ctxt("closure::load_environment");
237 // Load a pointer to the closure data, skipping over the box header:
238 let llcdata = at_box_body(bcx, cdata_ty, bcx.fcx.llenv.unwrap());
240 // Store the pointer to closure data in an alloca for debug info because that's what the
241 // llvm.dbg.declare intrinsic expects
242 let env_pointer_alloca = if bcx.sess().opts.debuginfo == FullDebugInfo {
243 let alloc = alloc_ty(bcx, ty::mk_mut_ptr(bcx.tcx(), cdata_ty), "__debuginfo_env_ptr");
244 Store(bcx, llcdata, alloc);
250 // Populate the upvars from the environment
252 for freevar in freevars.iter() {
253 let mut upvarptr = GEPi(bcx, llcdata, &[0u, i]);
254 let captured_by_ref = match store {
255 ty::RegionTraitStore(..) => {
256 upvarptr = Load(bcx, upvarptr);
259 ty::UniqTraitStore => false
261 let def_id = freevar.def.def_id();
263 bcx.fcx.llupvars.borrow_mut().insert(def_id.node, upvarptr);
264 if let Some(env_pointer_alloca) = env_pointer_alloca {
265 debuginfo::create_captured_var_metadata(
280 fn load_unboxed_closure_environment<'blk, 'tcx>(
281 bcx: Block<'blk, 'tcx>,
282 arg_scope_id: ScopeId,
283 freevar_mode: ast::CaptureClause,
284 freevars: &[ty::Freevar])
285 -> Block<'blk, 'tcx> {
286 let _icx = push_ctxt("closure::load_environment");
288 // Special case for small by-value selfs.
289 let closure_id = ast_util::local_def(bcx.fcx.id);
290 let self_type = self_type_for_unboxed_closure(bcx.ccx(), closure_id,
291 node_id_type(bcx, closure_id.node));
292 let kind = kind_for_unboxed_closure(bcx.ccx(), closure_id);
293 let llenv = if kind == ty::FnOnceUnboxedClosureKind &&
294 !arg_is_indirect(bcx.ccx(), self_type) {
295 let datum = rvalue_scratch_datum(bcx,
297 "unboxed_closure_env");
298 store_ty(bcx, bcx.fcx.llenv.unwrap(), datum.val, self_type);
301 bcx.fcx.llenv.unwrap()
304 // Store the pointer to closure data in an alloca for debug info because that's what the
305 // llvm.dbg.declare intrinsic expects
306 let env_pointer_alloca = if bcx.sess().opts.debuginfo == FullDebugInfo {
307 let alloc = alloca(bcx, val_ty(llenv), "__debuginfo_env_ptr");
308 Store(bcx, llenv, alloc);
314 for (i, freevar) in freevars.iter().enumerate() {
315 let mut upvar_ptr = GEPi(bcx, llenv, &[0, i]);
316 let captured_by_ref = match freevar_mode {
317 ast::CaptureByRef => {
318 upvar_ptr = Load(bcx, upvar_ptr);
321 ast::CaptureByValue => false
323 let def_id = freevar.def.def_id();
324 bcx.fcx.llupvars.borrow_mut().insert(def_id.node, upvar_ptr);
326 if kind == ty::FnOnceUnboxedClosureKind && freevar_mode == ast::CaptureByValue {
327 bcx.fcx.schedule_drop_mem(arg_scope_id,
329 node_id_type(bcx, def_id.node))
332 if let Some(env_pointer_alloca) = env_pointer_alloca {
333 debuginfo::create_captured_var_metadata(
346 fn fill_fn_pair(bcx: Block, pair: ValueRef, llfn: ValueRef, llenvptr: ValueRef) {
347 Store(bcx, llfn, GEPi(bcx, pair, &[0u, abi::FAT_PTR_ADDR]));
348 let llenvptr = PointerCast(bcx, llenvptr, Type::i8p(bcx.ccx()));
349 Store(bcx, llenvptr, GEPi(bcx, pair, &[0u, abi::FAT_PTR_EXTRA]));
353 pub enum ClosureKind<'tcx> {
355 // See load_environment.
356 BoxedClosure(Ty<'tcx>, ty::TraitStore),
357 // See load_unboxed_closure_environment.
358 UnboxedClosure(ast::CaptureClause)
361 pub struct ClosureEnv<'a, 'tcx> {
362 freevars: &'a [ty::Freevar],
363 pub kind: ClosureKind<'tcx>
366 impl<'a, 'tcx> ClosureEnv<'a, 'tcx> {
367 pub fn new(freevars: &'a [ty::Freevar], kind: ClosureKind<'tcx>)
368 -> ClosureEnv<'a, 'tcx> {
375 pub fn load<'blk>(self, bcx: Block<'blk, 'tcx>, arg_scope: ScopeId)
376 -> Block<'blk, 'tcx> {
377 // Don't bother to create the block if there's nothing to load
378 if self.freevars.is_empty() {
384 BoxedClosure(cdata_ty, store) => {
385 load_environment(bcx, cdata_ty, self.freevars, store)
387 UnboxedClosure(freevar_mode) => {
388 load_unboxed_closure_environment(bcx, arg_scope, freevar_mode, self.freevars)
394 /// Translates the body of a closure expression.
399 /// - `id`: The id of the closure expression.
400 /// - `cap_clause`: information about captured variables, if any.
401 /// - `dest`: where to write the closure value, which must be a
402 /// (fn ptr, env) pair
403 pub fn trans_expr_fn<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
404 store: ty::TraitStore,
409 -> Block<'blk, 'tcx> {
410 let _icx = push_ctxt("closure::trans_expr_fn");
412 let dest_addr = match dest {
413 expr::SaveIn(p) => p,
415 return bcx; // closure construction is non-side-effecting
421 let fty = node_id_type(bcx, id);
422 let s = tcx.map.with_path(id, |path| {
423 mangle_internal_name_by_path_and_seq(path, "closure")
425 let llfn = decl_internal_rust_fn(ccx, fty, s[]);
427 // set an inline hint for all closures
428 set_inline_hint(llfn);
430 let freevar_mode = tcx.capture_mode(id);
431 let freevars: Vec<ty::Freevar> =
432 ty::with_freevars(tcx, id, |fv| fv.iter().map(|&fv| fv).collect());
438 } = build_closure(bcx, freevar_mode, &freevars);
444 bcx.fcx.param_substs,
449 ClosureEnv::new(freevars[],
450 BoxedClosure(cdata_ty, store)));
451 fill_fn_pair(bcx, dest_addr, llfn, llbox);
455 /// Returns the LLVM function declaration for an unboxed closure, creating it
456 /// if necessary. If the ID does not correspond to a closure ID, returns None.
457 pub fn get_or_create_declaration_if_unboxed_closure<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
458 closure_id: ast::DefId,
459 substs: &Substs<'tcx>)
460 -> Option<Datum<'tcx, Rvalue>> {
461 if !ccx.tcx().unboxed_closures.borrow().contains_key(&closure_id) {
462 // Not an unboxed closure.
466 let function_type = ty::node_id_to_type(ccx.tcx(), closure_id.node);
467 let function_type = monomorphize::apply_param_substs(ccx.tcx(), substs, &function_type);
469 // Normalize type so differences in regions and typedefs don't cause
470 // duplicate declarations
471 let function_type = ty::normalize_ty(ccx.tcx(), function_type);
472 let params = match function_type.sty {
473 ty::ty_unboxed_closure(_, _, ref substs) => substs.types.clone(),
476 let mono_id = MonoId {
481 match ccx.unboxed_closure_vals().borrow().get(&mono_id) {
483 debug!("get_or_create_declaration_if_unboxed_closure(): found \
485 return Some(Datum::new(llfn, function_type, Rvalue::new(ByValue)))
490 let symbol = ccx.tcx().map.with_path(closure_id.node, |path| {
491 mangle_internal_name_by_path_and_seq(path, "unboxed_closure")
494 let llfn = decl_internal_rust_fn(ccx, function_type, symbol[]);
496 // set an inline hint for all closures
497 set_inline_hint(llfn);
499 debug!("get_or_create_declaration_if_unboxed_closure(): inserting new \
500 closure {} (type {})",
502 ccx.tn().type_to_string(val_ty(llfn)));
503 ccx.unboxed_closure_vals().borrow_mut().insert(mono_id, llfn);
505 Some(Datum::new(llfn, function_type, Rvalue::new(ByValue)))
508 pub fn trans_unboxed_closure<'blk, 'tcx>(
509 mut bcx: Block<'blk, 'tcx>,
516 let _icx = push_ctxt("closure::trans_unboxed_closure");
518 debug!("trans_unboxed_closure()");
520 let closure_id = ast_util::local_def(id);
521 let llfn = get_or_create_declaration_if_unboxed_closure(
524 bcx.fcx.param_substs).unwrap();
526 // Get the type of this closure. Use the current `param_substs` as
527 // the closure substitutions. This makes sense because the closure
528 // takes the same set of type arguments as the enclosing fn, and
529 // this function (`trans_unboxed_closure`) is invoked at the point
530 // of the closure expression.
531 let typer = NormalizingUnboxedClosureTyper::new(bcx.tcx());
532 let function_type = typer.unboxed_closure_type(closure_id, bcx.fcx.param_substs);
533 let function_type = ty::mk_closure(bcx.tcx(), function_type);
535 let freevars: Vec<ty::Freevar> =
536 ty::with_freevars(bcx.tcx(), id, |fv| fv.iter().map(|&fv| fv).collect());
537 let freevar_mode = bcx.tcx().capture_mode(id);
539 trans_closure(bcx.ccx(),
543 bcx.fcx.param_substs,
546 ty::ty_fn_ret(function_type),
547 ty::ty_fn_abi(function_type),
548 ClosureEnv::new(freevars[],
549 UnboxedClosure(freevar_mode)));
551 // Don't hoist this to the top of the function. It's perfectly legitimate
552 // to have a zero-size unboxed closure (in which case dest will be
553 // `Ignore`) and we must still generate the closure body.
554 let dest_addr = match dest {
555 expr::SaveIn(p) => p,
557 debug!("trans_unboxed_closure() ignoring result");
562 let repr = adt::represent_type(bcx.ccx(), node_id_type(bcx, id));
564 // Create the closure.
565 for (i, freevar) in freevars.iter().enumerate() {
566 let datum = expr::trans_local_var(bcx, freevar.def);
567 let upvar_slot_dest = adt::trans_field_ptr(bcx,
573 ast::CaptureByValue => {
574 bcx = datum.store_to(bcx, upvar_slot_dest);
576 ast::CaptureByRef => {
577 Store(bcx, datum.to_llref(), upvar_slot_dest);
581 adt::trans_set_discr(bcx, &*repr, dest_addr, 0);
586 pub fn get_wrapper_for_bare_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
587 closure_ty: Ty<'tcx>,
590 is_local: bool) -> ValueRef {
592 match ccx.closure_bare_wrapper_cache().borrow().get(&fn_ptr) {
593 Some(&llval) => return llval,
599 debug!("get_wrapper_for_bare_fn(closure_ty={})", closure_ty.repr(tcx));
601 let f = match closure_ty.sty {
602 ty::ty_closure(ref f) => f,
604 ccx.sess().bug(format!("get_wrapper_for_bare_fn: \
605 expected a closure ty, got {}",
606 closure_ty.repr(tcx))[]);
610 let name = ty::with_path(tcx, def_id, |path| {
611 mangle_internal_name_by_path_and_seq(path, "as_closure")
613 let llfn = if is_local {
614 decl_internal_rust_fn(ccx, closure_ty, name[])
616 decl_rust_fn(ccx, closure_ty, name[])
619 ccx.closure_bare_wrapper_cache().borrow_mut().insert(fn_ptr, llfn);
621 // This is only used by statics inlined from a different crate.
623 // Don't regenerate the wrapper, just reuse the original one.
627 let _icx = push_ctxt("closure::get_wrapper_for_bare_fn");
629 let arena = TypedArena::new();
630 let empty_param_substs = Substs::trans_empty();
631 let fcx = new_fn_ctxt(ccx, llfn, ast::DUMMY_NODE_ID, true, f.sig.0.output,
632 &empty_param_substs, None, &arena);
633 let bcx = init_function(&fcx, true, f.sig.0.output);
635 let args = create_datums_for_fn_args(&fcx,
636 ty::ty_fn_args(closure_ty)
638 let mut llargs = Vec::new();
639 match fcx.llretslotptr.get() {
641 assert!(!fcx.needs_ret_allocas);
642 llargs.push(llretptr);
646 llargs.extend(args.iter().map(|arg| arg.val));
648 let retval = Call(bcx, fn_ptr, llargs.as_slice(), None);
649 match f.sig.0.output {
650 ty::FnConverging(output_type) => {
651 if return_type_is_void(ccx, output_type) || fcx.llretslotptr.get().is_some() {
662 // HACK(eddyb) finish_fn cannot be used here, we returned directly.
663 debuginfo::clear_source_location(&fcx);
669 pub fn make_closure_from_bare_fn<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
670 closure_ty: Ty<'tcx>,
673 -> DatumBlock<'blk, 'tcx, Expr> {
674 let scratch = rvalue_scratch_datum(bcx, closure_ty, "__adjust");
675 let wrapper = get_wrapper_for_bare_fn(bcx.ccx(), closure_ty, def_id, fn_ptr, true);
676 fill_fn_pair(bcx, scratch.val, wrapper, C_null(Type::i8p(bcx.ccx())));
678 DatumBlock::new(bcx, scratch.to_expr_datum())