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 //! # Compilation of match statements
13 //! I will endeavor to explain the code as best I can. I have only a loose
14 //! understanding of some parts of it.
18 //! The basic state of the code is maintained in an array `m` of `Match`
19 //! objects. Each `Match` describes some list of patterns, all of which must
20 //! match against the current list of values. If those patterns match, then
21 //! the arm listed in the match is the correct arm. A given arm may have
22 //! multiple corresponding match entries, one for each alternative that
23 //! remains. As we proceed these sets of matches are adjusted by the various
24 //! `enter_XXX()` functions, each of which adjusts the set of options given
25 //! some information about the value which has been matched.
27 //! So, initially, there is one value and N matches, each of which have one
28 //! constituent pattern. N here is usually the number of arms but may be
29 //! greater, if some arms have multiple alternatives. For example, here:
31 //! enum Foo { A, B(int), C(uint, uint) }
39 //! The value would be `foo`. There would be four matches, each of which
40 //! contains one pattern (and, in one case, a guard). We could collect the
41 //! various options and then compile the code for the case where `foo` is an
42 //! `A`, a `B`, and a `C`. When we generate the code for `C`, we would (1)
43 //! drop the two matches that do not match a `C` and (2) expand the other two
44 //! into two patterns each. In the first case, the two patterns would be `1u`
45 //! and `2`, and the in the second case the _ pattern would be expanded into
46 //! `_` and `_`. The two values are of course the arguments to `C`.
48 //! Here is a quick guide to the various functions:
50 //! - `compile_submatch()`: The main workhouse. It takes a list of values and
51 //! a list of matches and finds the various possibilities that could occur.
53 //! - `enter_XXX()`: modifies the list of matches based on some information
54 //! about the value that has been matched. For example,
55 //! `enter_rec_or_struct()` adjusts the values given that a record or struct
56 //! has been matched. This is an infallible pattern, so *all* of the matches
57 //! must be either wildcards or record/struct patterns. `enter_opt()`
58 //! handles the fallible cases, and it is correspondingly more complex.
62 //! We store information about the bound variables for each arm as part of the
63 //! per-arm `ArmData` struct. There is a mapping from identifiers to
64 //! `BindingInfo` structs. These structs contain the mode/id/type of the
65 //! binding, but they also contain an LLVM value which points at an alloca
66 //! called `llmatch`. For by value bindings that are Copy, we also create
67 //! an extra alloca that we copy the matched value to so that any changes
68 //! we do to our copy is not reflected in the original and vice-versa.
69 //! We don't do this if it's a move since the original value can't be used
70 //! and thus allowing us to cheat in not creating an extra alloca.
72 //! The `llmatch` binding always stores a pointer into the value being matched
73 //! which points at the data for the binding. If the value being matched has
74 //! type `T`, then, `llmatch` will point at an alloca of type `T*` (and hence
75 //! `llmatch` has type `T**`). So, if you have a pattern like:
79 //! match (a, b) { (ref c, d) => { ... } }
81 //! For `c` and `d`, we would generate allocas of type `C*` and `D*`
82 //! respectively. These are called the `llmatch`. As we match, when we come
83 //! up against an identifier, we store the current pointer into the
84 //! corresponding alloca.
86 //! Once a pattern is completely matched, and assuming that there is no guard
87 //! pattern, we will branch to a block that leads to the body itself. For any
88 //! by-value bindings, this block will first load the ptr from `llmatch` (the
89 //! one of type `D*`) and then load a second time to get the actual value (the
90 //! one of type `D`). For by ref bindings, the value of the local variable is
91 //! simply the first alloca.
93 //! So, for the example above, we would generate a setup kind of like this:
99 //! +--------------------------------------------+
100 //! | llmatch_c = (addr of first half of tuple) |
101 //! | llmatch_d = (addr of second half of tuple) |
102 //! +--------------------------------------------+
104 //! +--------------------------------------+
105 //! | *llbinding_d = **llmatch_d |
106 //! +--------------------------------------+
108 //! If there is a guard, the situation is slightly different, because we must
109 //! execute the guard code. Moreover, we need to do so once for each of the
110 //! alternatives that lead to the arm, because if the guard fails, they may
111 //! have different points from which to continue the search. Therefore, in that
112 //! case, we generate code that looks more like:
118 //! +-------------------------------------------+
119 //! | llmatch_c = (addr of first half of tuple) |
120 //! | llmatch_d = (addr of first half of tuple) |
121 //! +-------------------------------------------+
123 //! +-------------------------------------------------+
124 //! | *llbinding_d = **llmatch_d |
125 //! | check condition |
126 //! | if false { goto next case } |
127 //! | if true { goto body } |
128 //! +-------------------------------------------------+
130 //! The handling for the cleanups is a bit... sensitive. Basically, the body
131 //! is the one that invokes `add_clean()` for each binding. During the guard
132 //! evaluation, we add temporary cleanups and revoke them after the guard is
133 //! evaluated (it could fail, after all). Note that guards and moves are
134 //! just plain incompatible.
136 //! Some relevant helper functions that manage bindings:
137 //! - `create_bindings_map()`
138 //! - `insert_lllocals()`
141 //! ## Notes on vector pattern matching.
143 //! Vector pattern matching is surprisingly tricky. The problem is that
144 //! the structure of the vector isn't fully known, and slice matches
145 //! can be done on subparts of it.
147 //! The way that vector pattern matches are dealt with, then, is as
148 //! follows. First, we make the actual condition associated with a
149 //! vector pattern simply a vector length comparison. So the pattern
150 //! [1, .. x] gets the condition "vec len >= 1", and the pattern
151 //! [.. x] gets the condition "vec len >= 0". The problem here is that
152 //! having the condition "vec len >= 1" hold clearly does not mean that
153 //! only a pattern that has exactly that condition will match. This
154 //! means that it may well be the case that a condition holds, but none
155 //! of the patterns matching that condition match; to deal with this,
156 //! when doing vector length matches, we have match failures proceed to
157 //! the next condition to check.
159 //! There are a couple more subtleties to deal with. While the "actual"
160 //! condition associated with vector length tests is simply a test on
161 //! the vector length, the actual vec_len Opt entry contains more
162 //! information used to restrict which matches are associated with it.
163 //! So that all matches in a submatch are matching against the same
164 //! values from inside the vector, they are split up by how many
165 //! elements they match at the front and at the back of the vector. In
166 //! order to make sure that arms are properly checked in order, even
167 //! with the overmatching conditions, each vec_len Opt entry is
168 //! associated with a range of matches.
169 //! Consider the following:
171 //! match &[1, 2, 3] {
172 //! [1, 1, .. _] => 0,
173 //! [1, 2, 2, .. _] => 1,
174 //! [1, 2, 3, .. _] => 2,
175 //! [1, 2, .. _] => 3,
178 //! The proper arm to match is arm 2, but arms 0 and 3 both have the
179 //! condition "len >= 2". If arm 3 was lumped in with arm 0, then the
180 //! wrong branch would be taken. Instead, vec_len Opts are associated
181 //! with a contiguous range of matches that have the same "shape".
182 //! This is sort of ugly and requires a bunch of special handling of
185 pub use self::BranchKind::*;
186 pub use self::OptResult::*;
187 pub use self::TransBindingMode::*;
189 use self::FailureHandler::*;
192 use llvm::{ValueRef, BasicBlockRef};
193 use middle::check_match::StaticInliner;
194 use middle::check_match;
195 use middle::const_eval;
196 use middle::def::{self, DefMap};
197 use middle::expr_use_visitor as euv;
198 use middle::lang_items::StrEqFnLangItem;
199 use middle::mem_categorization as mc;
200 use middle::pat_util::*;
203 use trans::build::{AddCase, And, BitCast, Br, CondBr, GEPi, InBoundsGEP, Load};
204 use trans::build::{Mul, Not, Store, Sub, add_comment};
207 use trans::cleanup::{self, CleanupMethods};
208 use trans::common::*;
211 use trans::expr::{self, Dest};
214 use trans::debuginfo;
215 use middle::ty::{self, Ty};
216 use session::config::FullDebugInfo;
217 use util::common::indenter;
218 use util::nodemap::FnvHashMap;
219 use util::ppaux::{Repr, vec_map_to_string};
222 use std::iter::AdditiveIterator;
225 use syntax::ast::{DUMMY_NODE_ID, Ident};
226 use syntax::codemap::Span;
227 use syntax::fold::Folder;
230 #[derive(Copy, Show)]
231 struct ConstantExpr<'a>(&'a ast::Expr);
233 impl<'a> ConstantExpr<'a> {
234 fn eq(self, other: ConstantExpr<'a>, tcx: &ty::ctxt) -> bool {
235 let ConstantExpr(expr) = self;
236 let ConstantExpr(other_expr) = other;
237 match const_eval::compare_lit_exprs(tcx, expr, other_expr) {
238 Some(val1) => val1 == 0,
239 None => panic!("compare_list_exprs: type mismatch"),
244 // An option identifying a branch (either a literal, an enum variant or a range)
247 ConstantValue(ConstantExpr<'a>),
248 ConstantRange(ConstantExpr<'a>, ConstantExpr<'a>),
249 Variant(ty::Disr, Rc<adt::Repr<'tcx>>, ast::DefId),
250 SliceLengthEqual(uint),
251 SliceLengthGreaterOrEqual(/* prefix length */ uint, /* suffix length */ uint),
254 impl<'a, 'tcx> Opt<'a, 'tcx> {
255 fn eq(&self, other: &Opt<'a, 'tcx>, tcx: &ty::ctxt<'tcx>) -> bool {
256 match (self, other) {
257 (&ConstantValue(a), &ConstantValue(b)) => a.eq(b, tcx),
258 (&ConstantRange(a1, a2), &ConstantRange(b1, b2)) => {
259 a1.eq(b1, tcx) && a2.eq(b2, tcx)
261 (&Variant(a_disr, ref a_repr, a_def), &Variant(b_disr, ref b_repr, b_def)) => {
262 a_disr == b_disr && *a_repr == *b_repr && a_def == b_def
264 (&SliceLengthEqual(a), &SliceLengthEqual(b)) => a == b,
265 (&SliceLengthGreaterOrEqual(a1, a2), &SliceLengthGreaterOrEqual(b1, b2)) => {
272 fn trans<'blk>(&self, mut bcx: Block<'blk, 'tcx>) -> OptResult<'blk, 'tcx> {
273 let _icx = push_ctxt("match::trans_opt");
276 ConstantValue(ConstantExpr(lit_expr)) => {
277 let lit_ty = ty::node_id_to_type(bcx.tcx(), lit_expr.id);
278 let (llval, _) = consts::const_expr(ccx, &*lit_expr);
279 let lit_datum = immediate_rvalue(llval, lit_ty);
280 let lit_datum = unpack_datum!(bcx, lit_datum.to_appropriate_datum(bcx));
281 SingleResult(Result::new(bcx, lit_datum.val))
283 ConstantRange(ConstantExpr(ref l1), ConstantExpr(ref l2)) => {
284 let (l1, _) = consts::const_expr(ccx, &**l1);
285 let (l2, _) = consts::const_expr(ccx, &**l2);
286 RangeResult(Result::new(bcx, l1), Result::new(bcx, l2))
288 Variant(disr_val, ref repr, _) => {
289 adt::trans_case(bcx, &**repr, disr_val)
291 SliceLengthEqual(length) => {
292 SingleResult(Result::new(bcx, C_uint(ccx, length)))
294 SliceLengthGreaterOrEqual(prefix, suffix) => {
295 LowerBound(Result::new(bcx, C_uint(ccx, prefix + suffix)))
301 #[derive(Copy, PartialEq)]
302 pub enum BranchKind {
310 pub enum OptResult<'blk, 'tcx: 'blk> {
311 SingleResult(Result<'blk, 'tcx>),
312 RangeResult(Result<'blk, 'tcx>, Result<'blk, 'tcx>),
313 LowerBound(Result<'blk, 'tcx>)
316 #[derive(Clone, Copy)]
317 pub enum TransBindingMode {
318 TrByCopy(/* llbinding */ ValueRef),
323 /// Information about a pattern binding:
324 /// - `llmatch` is a pointer to a stack slot. The stack slot contains a
325 /// pointer into the value being matched. Hence, llmatch has type `T**`
326 /// where `T` is the value being matched.
327 /// - `trmode` is the trans binding mode
328 /// - `id` is the node id of the binding
329 /// - `ty` is the Rust type of the binding
330 #[derive(Clone, Copy)]
331 pub struct BindingInfo<'tcx> {
332 pub llmatch: ValueRef,
333 pub trmode: TransBindingMode,
339 type BindingsMap<'tcx> = FnvHashMap<Ident, BindingInfo<'tcx>>;
341 struct ArmData<'p, 'blk, 'tcx: 'blk> {
342 bodycx: Block<'blk, 'tcx>,
344 bindings_map: BindingsMap<'tcx>
347 /// Info about Match.
348 /// If all `pats` are matched then arm `data` will be executed.
349 /// As we proceed `bound_ptrs` are filled with pointers to values to be bound,
350 /// these pointers are stored in llmatch variables just before executing `data` arm.
351 struct Match<'a, 'p: 'a, 'blk: 'a, 'tcx: 'blk> {
352 pats: Vec<&'p ast::Pat>,
353 data: &'a ArmData<'p, 'blk, 'tcx>,
354 bound_ptrs: Vec<(Ident, ValueRef)>,
357 impl<'a, 'p, 'blk, 'tcx> Repr<'tcx> for Match<'a, 'p, 'blk, 'tcx> {
358 fn repr(&self, tcx: &ty::ctxt) -> String {
359 if tcx.sess.verbose() {
360 // for many programs, this just take too long to serialize
363 format!("{} pats", self.pats.len())
368 fn has_nested_bindings(m: &[Match], col: uint) -> bool {
370 match br.pats[col].node {
371 ast::PatIdent(_, _, Some(_)) => return true,
378 fn expand_nested_bindings<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
379 m: &[Match<'a, 'p, 'blk, 'tcx>],
382 -> Vec<Match<'a, 'p, 'blk, 'tcx>> {
383 debug!("expand_nested_bindings(bcx={}, m={}, col={}, val={})",
387 bcx.val_to_string(val));
388 let _indenter = indenter();
391 let mut bound_ptrs = br.bound_ptrs.clone();
392 let mut pat = br.pats[col];
394 pat = match pat.node {
395 ast::PatIdent(_, ref path, Some(ref inner)) => {
396 bound_ptrs.push((path.node, val));
403 let mut pats = br.pats.clone();
408 bound_ptrs: bound_ptrs
413 fn enter_match<'a, 'b, 'p, 'blk, 'tcx, F>(bcx: Block<'blk, 'tcx>,
415 m: &[Match<'a, 'p, 'blk, 'tcx>],
419 -> Vec<Match<'a, 'p, 'blk, 'tcx>> where
420 F: FnMut(&[&'p ast::Pat]) -> Option<Vec<&'p ast::Pat>>,
422 debug!("enter_match(bcx={}, m={}, col={}, val={})",
426 bcx.val_to_string(val));
427 let _indenter = indenter();
429 m.iter().filter_map(|br| {
430 e(br.pats[]).map(|pats| {
431 let this = br.pats[col];
432 let mut bound_ptrs = br.bound_ptrs.clone();
434 ast::PatIdent(_, ref path, None) => {
435 if pat_is_binding(dm, &*this) {
436 bound_ptrs.push((path.node, val));
439 ast::PatVec(ref before, Some(ref slice), ref after) => {
440 if let ast::PatIdent(_, ref path, None) = slice.node {
441 let subslice_val = bind_subslice_pat(
443 before.len(), after.len());
444 bound_ptrs.push((path.node, subslice_val));
452 bound_ptrs: bound_ptrs
458 fn enter_default<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
460 m: &[Match<'a, 'p, 'blk, 'tcx>],
463 -> Vec<Match<'a, 'p, 'blk, 'tcx>> {
464 debug!("enter_default(bcx={}, m={}, col={}, val={})",
468 bcx.val_to_string(val));
469 let _indenter = indenter();
471 // Collect all of the matches that can match against anything.
472 enter_match(bcx, dm, m, col, val, |pats| {
473 if pat_is_binding_or_wild(dm, &*pats[col]) {
474 let mut r = pats[..col].to_vec();
475 r.push_all(pats[col + 1..]);
483 // <pcwalton> nmatsakis: what does enter_opt do?
484 // <pcwalton> in trans/match
485 // <pcwalton> trans/match.rs is like stumbling around in a dark cave
486 // <nmatsakis> pcwalton: the enter family of functions adjust the set of
487 // patterns as needed
488 // <nmatsakis> yeah, at some point I kind of achieved some level of
490 // <nmatsakis> anyhow, they adjust the patterns given that something of that
491 // kind has been found
492 // <nmatsakis> pcwalton: ok, right, so enter_XXX() adjusts the patterns, as I
494 // <nmatsakis> enter_match() kind of embodies the generic code
495 // <nmatsakis> it is provided with a function that tests each pattern to see
496 // if it might possibly apply and so forth
497 // <nmatsakis> so, if you have a pattern like {a: _, b: _, _} and one like _
498 // <nmatsakis> then _ would be expanded to (_, _)
499 // <nmatsakis> one spot for each of the sub-patterns
500 // <nmatsakis> enter_opt() is one of the more complex; it covers the fallible
502 // <nmatsakis> enter_rec_or_struct() or enter_tuple() are simpler, since they
503 // are infallible patterns
504 // <nmatsakis> so all patterns must either be records (resp. tuples) or
507 /// The above is now outdated in that enter_match() now takes a function that
508 /// takes the complete row of patterns rather than just the first one.
509 /// Also, most of the enter_() family functions have been unified with
510 /// the check_match specialization step.
511 fn enter_opt<'a, 'p, 'blk, 'tcx>(
512 bcx: Block<'blk, 'tcx>,
515 m: &[Match<'a, 'p, 'blk, 'tcx>],
520 -> Vec<Match<'a, 'p, 'blk, 'tcx>> {
521 debug!("enter_opt(bcx={}, m={}, opt={}, col={}, val={})",
526 bcx.val_to_string(val));
527 let _indenter = indenter();
529 let ctor = match opt {
530 &ConstantValue(ConstantExpr(expr)) => check_match::ConstantValue(
531 const_eval::eval_const_expr(bcx.tcx(), &*expr)
533 &ConstantRange(ConstantExpr(lo), ConstantExpr(hi)) => check_match::ConstantRange(
534 const_eval::eval_const_expr(bcx.tcx(), &*lo),
535 const_eval::eval_const_expr(bcx.tcx(), &*hi)
537 &SliceLengthEqual(n) =>
538 check_match::Slice(n),
539 &SliceLengthGreaterOrEqual(before, after) =>
540 check_match::SliceWithSubslice(before, after),
541 &Variant(_, _, def_id) =>
542 check_match::Constructor::Variant(def_id)
545 let param_env = ty::empty_parameter_environment(bcx.tcx());
546 let mcx = check_match::MatchCheckCtxt {
548 param_env: param_env,
550 enter_match(bcx, dm, m, col, val, |pats|
551 check_match::specialize(&mcx, pats[], &ctor, col, variant_size)
555 // Returns the options in one column of matches. An option is something that
556 // needs to be conditionally matched at runtime; for example, the discriminant
557 // on a set of enum variants or a literal.
558 fn get_branches<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
559 m: &[Match<'a, 'p, 'blk, 'tcx>], col: uint)
560 -> Vec<Opt<'p, 'tcx>> {
563 let mut found: Vec<Opt> = vec![];
565 let cur = br.pats[col];
566 let opt = match cur.node {
567 ast::PatLit(ref l) => ConstantValue(ConstantExpr(&**l)),
568 ast::PatIdent(..) | ast::PatEnum(..) | ast::PatStruct(..) => {
569 // This is either an enum variant or a variable binding.
570 let opt_def = tcx.def_map.borrow().get(&cur.id).cloned();
572 Some(def::DefVariant(enum_id, var_id, _)) => {
573 let variant = ty::enum_variant_with_id(tcx, enum_id, var_id);
574 Variant(variant.disr_val, adt::represent_node(bcx, cur.id), var_id)
579 ast::PatRange(ref l1, ref l2) => {
580 ConstantRange(ConstantExpr(&**l1), ConstantExpr(&**l2))
582 ast::PatVec(ref before, None, ref after) => {
583 SliceLengthEqual(before.len() + after.len())
585 ast::PatVec(ref before, Some(_), ref after) => {
586 SliceLengthGreaterOrEqual(before.len(), after.len())
591 if !found.iter().any(|x| x.eq(&opt, tcx)) {
598 struct ExtractedBlock<'blk, 'tcx: 'blk> {
600 bcx: Block<'blk, 'tcx>,
603 fn extract_variant_args<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
604 repr: &adt::Repr<'tcx>,
607 -> ExtractedBlock<'blk, 'tcx> {
608 let _icx = push_ctxt("match::extract_variant_args");
609 let args = range(0, adt::num_args(repr, disr_val)).map(|i| {
610 adt::trans_field_ptr(bcx, repr, val, disr_val, i)
613 ExtractedBlock { vals: args, bcx: bcx }
616 /// Helper for converting from the ValueRef that we pass around in the match code, which is always
617 /// an lvalue, into a Datum. Eventually we should just pass around a Datum and be done with it.
618 fn match_datum<'tcx>(val: ValueRef, left_ty: Ty<'tcx>) -> Datum<'tcx, Lvalue> {
619 Datum::new(val, left_ty, Lvalue)
622 fn bind_subslice_pat(bcx: Block,
626 offset_right: uint) -> ValueRef {
627 let _icx = push_ctxt("match::bind_subslice_pat");
628 let vec_ty = node_id_type(bcx, pat_id);
629 let vt = tvec::vec_types(bcx, ty::sequence_element_type(bcx.tcx(), ty::type_content(vec_ty)));
630 let vec_datum = match_datum(val, vec_ty);
631 let (base, len) = vec_datum.get_vec_base_and_len(bcx);
633 let slice_byte_offset = Mul(bcx, vt.llunit_size, C_uint(bcx.ccx(), offset_left));
634 let slice_begin = tvec::pointer_add_byte(bcx, base, slice_byte_offset);
635 let slice_len_offset = C_uint(bcx.ccx(), offset_left + offset_right);
636 let slice_len = Sub(bcx, len, slice_len_offset);
637 let slice_ty = ty::mk_slice(bcx.tcx(),
638 bcx.tcx().mk_region(ty::ReStatic),
639 ty::mt {ty: vt.unit_ty, mutbl: ast::MutImmutable});
640 let scratch = rvalue_scratch_datum(bcx, slice_ty, "");
641 Store(bcx, slice_begin,
642 GEPi(bcx, scratch.val, &[0u, abi::FAT_PTR_ADDR]));
643 Store(bcx, slice_len, GEPi(bcx, scratch.val, &[0u, abi::FAT_PTR_EXTRA]));
647 fn extract_vec_elems<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
652 -> ExtractedBlock<'blk, 'tcx> {
653 let _icx = push_ctxt("match::extract_vec_elems");
654 let vec_datum = match_datum(val, left_ty);
655 let (base, len) = vec_datum.get_vec_base_and_len(bcx);
656 let mut elems = vec![];
657 elems.extend(range(0, before).map(|i| GEPi(bcx, base, &[i])));
658 elems.extend(range(0, after).rev().map(|i| {
659 InBoundsGEP(bcx, base, &[
660 Sub(bcx, len, C_uint(bcx.ccx(), i + 1))
663 ExtractedBlock { vals: elems, bcx: bcx }
666 // Macro for deciding whether any of the remaining matches fit a given kind of
667 // pattern. Note that, because the macro is well-typed, either ALL of the
668 // matches should fit that sort of pattern or NONE (however, some of the
669 // matches may be wildcards like _ or identifiers).
670 macro_rules! any_pat {
671 ($m:expr, $col:expr, $pattern:pat) => (
672 ($m).iter().any(|br| {
673 match br.pats[$col].node {
681 fn any_uniq_pat(m: &[Match], col: uint) -> bool {
682 any_pat!(m, col, ast::PatBox(_))
685 fn any_region_pat(m: &[Match], col: uint) -> bool {
686 any_pat!(m, col, ast::PatRegion(_))
689 fn any_irrefutable_adt_pat(tcx: &ty::ctxt, m: &[Match], col: uint) -> bool {
691 let pat = br.pats[col];
693 ast::PatTup(_) => true,
694 ast::PatStruct(..) => {
695 match tcx.def_map.borrow().get(&pat.id) {
696 Some(&def::DefVariant(..)) => false,
700 ast::PatEnum(..) | ast::PatIdent(_, _, None) => {
701 match tcx.def_map.borrow().get(&pat.id) {
702 Some(&def::DefStruct(..)) => true,
711 /// What to do when the pattern match fails.
712 enum FailureHandler {
714 JumpToBasicBlock(BasicBlockRef),
718 impl FailureHandler {
719 fn is_fallible(&self) -> bool {
726 fn is_infallible(&self) -> bool {
730 fn handle_fail(&self, bcx: Block) {
733 panic!("attempted to panic in a non-panicking panic handler!"),
734 JumpToBasicBlock(basic_block) =>
735 Br(bcx, basic_block),
737 build::Unreachable(bcx)
742 fn pick_column_to_specialize(def_map: &DefMap, m: &[Match]) -> Option<uint> {
743 fn pat_score(def_map: &DefMap, pat: &ast::Pat) -> uint {
745 ast::PatIdent(_, _, Some(ref inner)) => pat_score(def_map, &**inner),
746 _ if pat_is_refutable(def_map, pat) => 1u,
751 let column_score = |&: m: &[Match], col: uint| -> uint {
752 let total_score = m.iter()
753 .map(|row| row.pats[col])
754 .map(|pat| pat_score(def_map, pat))
757 // Irrefutable columns always go first, they'd only be duplicated in the branches.
758 if total_score == 0 {
765 let column_contains_any_nonwild_patterns = |&: &col: &uint| -> bool {
766 m.iter().any(|row| match row.pats[col].node {
767 ast::PatWild(_) => false,
772 range(0, m[0].pats.len())
773 .filter(column_contains_any_nonwild_patterns)
774 .map(|col| (col, column_score(m, col)))
775 .max_by(|&(_, score)| score)
779 // Compiles a comparison between two things.
780 fn compare_values<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
784 -> Result<'blk, 'tcx> {
785 fn compare_str<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
789 -> Result<'blk, 'tcx> {
790 let did = langcall(cx,
792 format!("comparison of `{}`",
793 cx.ty_to_string(rhs_t))[],
795 callee::trans_lang_call(cx, did, &[lhs, rhs], None)
798 let _icx = push_ctxt("compare_values");
799 if ty::type_is_scalar(rhs_t) {
800 let rs = compare_scalar_types(cx, lhs, rhs, rhs_t, ast::BiEq);
801 return Result::new(rs.bcx, rs.val);
805 ty::ty_rptr(_, mt) => match mt.ty.sty {
806 ty::ty_str => compare_str(cx, lhs, rhs, rhs_t),
807 ty::ty_vec(ty, _) => match ty.sty {
808 ty::ty_uint(ast::TyU8) => {
809 // NOTE: cast &[u8] to &str and abuse the str_eq lang item,
810 // which calls memcmp().
811 let t = ty::mk_str_slice(cx.tcx(),
812 cx.tcx().mk_region(ty::ReStatic),
814 let lhs = BitCast(cx, lhs, type_of::type_of(cx.ccx(), t).ptr_to());
815 let rhs = BitCast(cx, rhs, type_of::type_of(cx.ccx(), t).ptr_to());
816 compare_str(cx, lhs, rhs, rhs_t)
818 _ => cx.sess().bug("only byte strings supported in compare_values"),
820 _ => cx.sess().bug("only string and byte strings supported in compare_values"),
822 _ => cx.sess().bug("only scalars, byte strings, and strings supported in compare_values"),
826 /// For each binding in `data.bindings_map`, adds an appropriate entry into the `fcx.lllocals` map
827 fn insert_lllocals<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
828 bindings_map: &BindingsMap<'tcx>,
829 cs: Option<cleanup::ScopeId>)
830 -> Block<'blk, 'tcx> {
831 for (&ident, &binding_info) in bindings_map.iter() {
832 let llval = match binding_info.trmode {
833 // By value mut binding for a copy type: load from the ptr
834 // into the matched value and copy to our alloca
835 TrByCopy(llbinding) => {
836 let llval = Load(bcx, binding_info.llmatch);
837 let datum = Datum::new(llval, binding_info.ty, Lvalue);
838 call_lifetime_start(bcx, llbinding);
839 bcx = datum.store_to(bcx, llbinding);
840 if let Some(cs) = cs {
841 bcx.fcx.schedule_lifetime_end(cs, llbinding);
847 // By value move bindings: load from the ptr into the matched value
848 TrByMove => Load(bcx, binding_info.llmatch),
850 // By ref binding: use the ptr into the matched value
851 TrByRef => binding_info.llmatch
854 let datum = Datum::new(llval, binding_info.ty, Lvalue);
855 if let Some(cs) = cs {
856 bcx.fcx.schedule_drop_and_zero_mem(cs, llval, binding_info.ty);
857 bcx.fcx.schedule_lifetime_end(cs, binding_info.llmatch);
860 debug!("binding {} to {}",
862 bcx.val_to_string(llval));
863 bcx.fcx.lllocals.borrow_mut().insert(binding_info.id, datum);
865 if bcx.sess().opts.debuginfo == FullDebugInfo {
866 debuginfo::create_match_binding_metadata(bcx,
874 fn compile_guard<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
875 guard_expr: &ast::Expr,
876 data: &ArmData<'p, 'blk, 'tcx>,
877 m: &[Match<'a, 'p, 'blk, 'tcx>],
879 chk: &FailureHandler,
880 has_genuine_default: bool)
881 -> Block<'blk, 'tcx> {
882 debug!("compile_guard(bcx={}, guard_expr={}, m={}, vals={})",
884 bcx.expr_to_string(guard_expr),
886 vec_map_to_string(vals, |v| bcx.val_to_string(*v)));
887 let _indenter = indenter();
889 let mut bcx = insert_lllocals(bcx, &data.bindings_map, None);
891 let val = unpack_datum!(bcx, expr::trans(bcx, guard_expr));
892 let val = val.to_llbool(bcx);
894 for (_, &binding_info) in data.bindings_map.iter() {
895 if let TrByCopy(llbinding) = binding_info.trmode {
896 call_lifetime_end(bcx, llbinding);
900 with_cond(bcx, Not(bcx, val), |bcx| {
901 // Guard does not match: remove all bindings from the lllocals table
902 for (_, &binding_info) in data.bindings_map.iter() {
903 call_lifetime_end(bcx, binding_info.llmatch);
904 bcx.fcx.lllocals.borrow_mut().remove(&binding_info.id);
907 // If the default arm is the only one left, move on to the next
908 // condition explicitly rather than (possibly) falling back to
910 &JumpToBasicBlock(_) if m.len() == 1 && has_genuine_default => {
911 chk.handle_fail(bcx);
914 compile_submatch(bcx, m, vals, chk, has_genuine_default);
921 fn compile_submatch<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
922 m: &[Match<'a, 'p, 'blk, 'tcx>],
924 chk: &FailureHandler,
925 has_genuine_default: bool) {
926 debug!("compile_submatch(bcx={}, m={}, vals={})",
929 vec_map_to_string(vals, |v| bcx.val_to_string(*v)));
930 let _indenter = indenter();
931 let _icx = push_ctxt("match::compile_submatch");
934 if chk.is_fallible() {
935 chk.handle_fail(bcx);
941 let def_map = &tcx.def_map;
942 match pick_column_to_specialize(def_map, m) {
945 if has_nested_bindings(m, col) {
946 let expanded = expand_nested_bindings(bcx, m, col, val);
947 compile_submatch_continue(bcx,
955 compile_submatch_continue(bcx, m, vals, chk, col, val, has_genuine_default)
959 let data = &m[0].data;
960 for &(ref ident, ref value_ptr) in m[0].bound_ptrs.iter() {
961 let llmatch = data.bindings_map[*ident].llmatch;
962 call_lifetime_start(bcx, llmatch);
963 Store(bcx, *value_ptr, llmatch);
965 match data.arm.guard {
966 Some(ref guard_expr) => {
967 bcx = compile_guard(bcx,
973 has_genuine_default);
977 Br(bcx, data.bodycx.llbb);
982 fn compile_submatch_continue<'a, 'p, 'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
983 m: &[Match<'a, 'p, 'blk, 'tcx>],
985 chk: &FailureHandler,
988 has_genuine_default: bool) {
991 let dm = &tcx.def_map;
993 let mut vals_left = vals[0u..col].to_vec();
994 vals_left.push_all(vals[col + 1u..]);
995 let ccx = bcx.fcx.ccx;
997 // Find a real id (we're adding placeholder wildcard patterns, but
998 // each column is guaranteed to have at least one real pattern)
999 let pat_id = m.iter().map(|br| br.pats[col].id)
1000 .find(|&id| id != DUMMY_NODE_ID)
1001 .unwrap_or(DUMMY_NODE_ID);
1003 let left_ty = if pat_id == DUMMY_NODE_ID {
1006 node_id_type(bcx, pat_id)
1009 let mcx = check_match::MatchCheckCtxt {
1011 param_env: ty::empty_parameter_environment(bcx.tcx()),
1013 let adt_vals = if any_irrefutable_adt_pat(bcx.tcx(), m, col) {
1014 let repr = adt::represent_type(bcx.ccx(), left_ty);
1015 let arg_count = adt::num_args(&*repr, 0);
1016 let field_vals: Vec<ValueRef> = std::iter::range(0, arg_count).map(|ix|
1017 adt::trans_field_ptr(bcx, &*repr, val, 0, ix)
1020 } else if any_uniq_pat(m, col) || any_region_pat(m, col) {
1021 Some(vec!(Load(bcx, val)))
1024 ty::ty_vec(_, Some(n)) => {
1025 let args = extract_vec_elems(bcx, left_ty, n, 0, val);
1033 Some(field_vals) => {
1034 let pats = enter_match(bcx, dm, m, col, val, |pats|
1035 check_match::specialize(&mcx, pats,
1036 &check_match::Single, col,
1039 let mut vals = field_vals;
1040 vals.push_all(vals_left[]);
1041 compile_submatch(bcx, pats[], vals[], chk, has_genuine_default);
1047 // Decide what kind of branch we need
1048 let opts = get_branches(bcx, m, col);
1049 debug!("options={}", opts);
1050 let mut kind = NoBranch;
1051 let mut test_val = val;
1052 debug!("test_val={}", bcx.val_to_string(test_val));
1053 if opts.len() > 0u {
1055 ConstantValue(_) | ConstantRange(_, _) => {
1056 test_val = load_if_immediate(bcx, val, left_ty);
1057 kind = if ty::type_is_integral(left_ty) {
1063 Variant(_, ref repr, _) => {
1064 let (the_kind, val_opt) = adt::trans_switch(bcx, &**repr, val);
1066 for &tval in val_opt.iter() { test_val = tval; }
1068 SliceLengthEqual(_) | SliceLengthGreaterOrEqual(_, _) => {
1069 let (_, len) = tvec::get_base_and_len(bcx, val, left_ty);
1075 for o in opts.iter() {
1077 ConstantRange(_, _) => { kind = Compare; break },
1078 SliceLengthGreaterOrEqual(_, _) => { kind = CompareSliceLength; break },
1082 let else_cx = match kind {
1083 NoBranch | Single => bcx,
1084 _ => bcx.fcx.new_temp_block("match_else")
1086 let sw = if kind == Switch {
1087 build::Switch(bcx, test_val, else_cx.llbb, opts.len())
1089 C_int(ccx, 0i) // Placeholder for when not using a switch
1092 let defaults = enter_default(else_cx, dm, m, col, val);
1093 let exhaustive = chk.is_infallible() && defaults.len() == 0u;
1094 let len = opts.len();
1096 // Compile subtrees for each option
1097 for (i, opt) in opts.iter().enumerate() {
1098 // In some cases of range and vector pattern matching, we need to
1099 // override the failure case so that instead of failing, it proceeds
1100 // to try more matching. branch_chk, then, is the proper failure case
1101 // for the current conditional branch.
1102 let mut branch_chk = None;
1103 let mut opt_cx = else_cx;
1104 if !exhaustive || i + 1 < len {
1105 opt_cx = bcx.fcx.new_temp_block("match_case");
1107 Single => Br(bcx, opt_cx.llbb),
1109 match opt.trans(bcx) {
1110 SingleResult(r) => {
1111 AddCase(sw, r.val, opt_cx.llbb);
1116 "in compile_submatch, expected \
1117 opt.trans() to return a SingleResult")
1121 Compare | CompareSliceLength => {
1122 let t = if kind == Compare {
1125 tcx.types.uint // vector length
1127 let Result { bcx: after_cx, val: matches } = {
1128 match opt.trans(bcx) {
1129 SingleResult(Result { bcx, val }) => {
1130 compare_values(bcx, test_val, val, t)
1132 RangeResult(Result { val: vbegin, .. },
1133 Result { bcx, val: vend }) => {
1134 let Result { bcx, val: llge } =
1135 compare_scalar_types(
1137 vbegin, t, ast::BiGe);
1138 let Result { bcx, val: llle } =
1139 compare_scalar_types(
1140 bcx, test_val, vend,
1142 Result::new(bcx, And(bcx, llge, llle))
1144 LowerBound(Result { bcx, val }) => {
1145 compare_scalar_types(bcx, test_val, val, t, ast::BiGe)
1149 bcx = fcx.new_temp_block("compare_next");
1151 // If none of the sub-cases match, and the current condition
1152 // is guarded or has multiple patterns, move on to the next
1153 // condition, if there is any, rather than falling back to
1155 let guarded = m[i].data.arm.guard.is_some();
1156 let multi_pats = m[i].pats.len() > 1;
1157 if i + 1 < len && (guarded || multi_pats || kind == CompareSliceLength) {
1158 branch_chk = Some(JumpToBasicBlock(bcx.llbb));
1160 CondBr(after_cx, matches, opt_cx.llbb, bcx.llbb);
1164 } else if kind == Compare || kind == CompareSliceLength {
1165 Br(bcx, else_cx.llbb);
1169 let mut unpacked = Vec::new();
1171 Variant(disr_val, ref repr, _) => {
1172 let ExtractedBlock {vals: argvals, bcx: new_bcx} =
1173 extract_variant_args(opt_cx, &**repr, disr_val, val);
1174 size = argvals.len();
1178 SliceLengthEqual(len) => {
1179 let args = extract_vec_elems(opt_cx, left_ty, len, 0, val);
1180 size = args.vals.len();
1181 unpacked = args.vals.clone();
1184 SliceLengthGreaterOrEqual(before, after) => {
1185 let args = extract_vec_elems(opt_cx, left_ty, before, after, val);
1186 size = args.vals.len();
1187 unpacked = args.vals.clone();
1190 ConstantValue(_) | ConstantRange(_, _) => ()
1192 let opt_ms = enter_opt(opt_cx, pat_id, dm, m, opt, col, size, val);
1193 let mut opt_vals = unpacked;
1194 opt_vals.push_all(vals_left[]);
1195 compile_submatch(opt_cx,
1198 branch_chk.as_ref().unwrap_or(chk),
1199 has_genuine_default);
1202 // Compile the fall-through case, if any
1203 if !exhaustive && kind != Single {
1204 if kind == Compare || kind == CompareSliceLength {
1205 Br(bcx, else_cx.llbb);
1208 // If there is only one default arm left, move on to the next
1209 // condition explicitly rather than (eventually) falling back to
1210 // the last default arm.
1211 &JumpToBasicBlock(_) if defaults.len() == 1 && has_genuine_default => {
1212 chk.handle_fail(else_cx);
1215 compile_submatch(else_cx,
1219 has_genuine_default);
1225 pub fn trans_match<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
1226 match_expr: &ast::Expr,
1227 discr_expr: &ast::Expr,
1230 -> Block<'blk, 'tcx> {
1231 let _icx = push_ctxt("match::trans_match");
1232 trans_match_inner(bcx, match_expr.id, discr_expr, arms, dest)
1235 /// Checks whether the binding in `discr` is assigned to anywhere in the expression `body`
1236 fn is_discr_reassigned(bcx: Block, discr: &ast::Expr, body: &ast::Expr) -> bool {
1237 let (vid, field) = match discr.node {
1238 ast::ExprPath(..) => match bcx.def(discr.id) {
1239 def::DefLocal(vid) | def::DefUpvar(vid, _, _) => (vid, None),
1242 ast::ExprField(ref base, field) => {
1243 let vid = match bcx.tcx().def_map.borrow().get(&base.id) {
1244 Some(&def::DefLocal(vid)) | Some(&def::DefUpvar(vid, _, _)) => vid,
1247 (vid, Some(mc::NamedField(field.node.name)))
1249 ast::ExprTupField(ref base, field) => {
1250 let vid = match bcx.tcx().def_map.borrow().get(&base.id) {
1251 Some(&def::DefLocal(vid)) | Some(&def::DefUpvar(vid, _, _)) => vid,
1254 (vid, Some(mc::PositionalField(field.node)))
1259 let mut rc = ReassignmentChecker {
1265 let mut visitor = euv::ExprUseVisitor::new(&mut rc, bcx);
1266 visitor.walk_expr(body);
1271 struct ReassignmentChecker {
1273 field: Option<mc::FieldName>,
1277 // Determine if the expression we're matching on is reassigned to within
1278 // the body of the match's arm.
1279 // We only care for the `mutate` callback since this check only matters
1280 // for cases where the matched value is moved.
1281 impl<'tcx> euv::Delegate<'tcx> for ReassignmentChecker {
1282 fn consume(&mut self, _: ast::NodeId, _: Span, _: mc::cmt, _: euv::ConsumeMode) {}
1283 fn matched_pat(&mut self, _: &ast::Pat, _: mc::cmt, _: euv::MatchMode) {}
1284 fn consume_pat(&mut self, _: &ast::Pat, _: mc::cmt, _: euv::ConsumeMode) {}
1285 fn borrow(&mut self, _: ast::NodeId, _: Span, _: mc::cmt, _: ty::Region,
1286 _: ty::BorrowKind, _: euv::LoanCause) {}
1287 fn decl_without_init(&mut self, _: ast::NodeId, _: Span) {}
1289 fn mutate(&mut self, _: ast::NodeId, _: Span, cmt: mc::cmt, _: euv::MutateMode) {
1291 mc::cat_upvar(mc::Upvar { id: ty::UpvarId { var_id: vid, .. }, .. }) |
1292 mc::cat_local(vid) => self.reassigned = self.node == vid,
1293 mc::cat_interior(ref base_cmt, mc::InteriorField(field)) => {
1294 match base_cmt.cat {
1295 mc::cat_upvar(mc::Upvar { id: ty::UpvarId { var_id: vid, .. }, .. }) |
1296 mc::cat_local(vid) => {
1297 self.reassigned = self.node == vid && Some(field) == self.field
1307 fn create_bindings_map<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, pat: &ast::Pat,
1308 discr: &ast::Expr, body: &ast::Expr)
1309 -> BindingsMap<'tcx> {
1310 // Create the bindings map, which is a mapping from each binding name
1311 // to an alloca() that will be the value for that local variable.
1312 // Note that we use the names because each binding will have many ids
1313 // from the various alternatives.
1314 let ccx = bcx.ccx();
1315 let tcx = bcx.tcx();
1316 let reassigned = is_discr_reassigned(bcx, discr, body);
1317 let mut bindings_map = FnvHashMap::new();
1318 pat_bindings(&tcx.def_map, &*pat, |bm, p_id, span, path1| {
1319 let ident = path1.node;
1320 let variable_ty = node_id_type(bcx, p_id);
1321 let llvariable_ty = type_of::type_of(ccx, variable_ty);
1322 let tcx = bcx.tcx();
1323 let param_env = ty::empty_parameter_environment(tcx);
1329 if !ty::type_moves_by_default(¶m_env, span, variable_ty) || reassigned =>
1331 llmatch = alloca_no_lifetime(bcx,
1332 llvariable_ty.ptr_to(),
1334 trmode = TrByCopy(alloca_no_lifetime(bcx,
1336 bcx.ident(ident)[]));
1338 ast::BindByValue(_) => {
1339 // in this case, the final type of the variable will be T,
1340 // but during matching we need to store a *T as explained
1342 llmatch = alloca_no_lifetime(bcx,
1343 llvariable_ty.ptr_to(),
1344 bcx.ident(ident)[]);
1347 ast::BindByRef(_) => {
1348 llmatch = alloca_no_lifetime(bcx,
1350 bcx.ident(ident)[]);
1354 bindings_map.insert(ident, BindingInfo {
1362 return bindings_map;
1365 fn trans_match_inner<'blk, 'tcx>(scope_cx: Block<'blk, 'tcx>,
1366 match_id: ast::NodeId,
1367 discr_expr: &ast::Expr,
1369 dest: Dest) -> Block<'blk, 'tcx> {
1370 let _icx = push_ctxt("match::trans_match_inner");
1371 let fcx = scope_cx.fcx;
1372 let mut bcx = scope_cx;
1373 let tcx = bcx.tcx();
1375 let discr_datum = unpack_datum!(bcx, expr::trans_to_lvalue(bcx, discr_expr,
1377 if bcx.unreachable.get() {
1381 let t = node_id_type(bcx, discr_expr.id);
1382 let chk = if ty::type_is_empty(tcx, t) {
1388 let arm_datas: Vec<ArmData> = arms.iter().map(|arm| ArmData {
1389 bodycx: fcx.new_id_block("case_body", arm.body.id),
1391 bindings_map: create_bindings_map(bcx, &*arm.pats[0], discr_expr, &*arm.body)
1394 let mut static_inliner = StaticInliner::new(scope_cx.tcx());
1395 let arm_pats: Vec<Vec<P<ast::Pat>>> = arm_datas.iter().map(|arm_data| {
1396 arm_data.arm.pats.iter().map(|p| static_inliner.fold_pat((*p).clone())).collect()
1398 let mut matches = Vec::new();
1399 for (arm_data, pats) in arm_datas.iter().zip(arm_pats.iter()) {
1400 matches.extend(pats.iter().map(|p| Match {
1403 bound_ptrs: Vec::new(),
1407 // `compile_submatch` works one column of arm patterns a time and
1408 // then peels that column off. So as we progress, it may become
1409 // impossible to tell whether we have a genuine default arm, i.e.
1410 // `_ => foo` or not. Sometimes it is important to know that in order
1411 // to decide whether moving on to the next condition or falling back
1412 // to the default arm.
1413 let has_default = arms.last().map_or(false, |arm| {
1415 && arm.pats.last().unwrap().node == ast::PatWild(ast::PatWildSingle)
1418 compile_submatch(bcx, matches[], &[discr_datum.val], &chk, has_default);
1420 let mut arm_cxs = Vec::new();
1421 for arm_data in arm_datas.iter() {
1422 let mut bcx = arm_data.bodycx;
1424 // insert bindings into the lllocals map and add cleanups
1425 let cs = fcx.push_custom_cleanup_scope();
1426 bcx = insert_lllocals(bcx, &arm_data.bindings_map, Some(cleanup::CustomScope(cs)));
1427 bcx = expr::trans_into(bcx, &*arm_data.arm.body, dest);
1428 bcx = fcx.pop_and_trans_custom_cleanup_scope(bcx, cs);
1432 bcx = scope_cx.fcx.join_blocks(match_id, arm_cxs[]);
1436 /// Generates code for a local variable declaration like `let <pat>;` or `let <pat> =
1437 /// <opt_init_expr>`.
1438 pub fn store_local<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
1440 -> Block<'blk, 'tcx> {
1441 let _icx = push_ctxt("match::store_local");
1443 let tcx = bcx.tcx();
1444 let pat = &*local.pat;
1446 fn create_dummy_locals<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
1448 -> Block<'blk, 'tcx> {
1449 // create dummy memory for the variables if we have no
1450 // value to store into them immediately
1451 let tcx = bcx.tcx();
1452 pat_bindings(&tcx.def_map, pat, |_, p_id, _, path1| {
1453 let scope = cleanup::var_scope(tcx, p_id);
1454 bcx = mk_binding_alloca(
1455 bcx, p_id, &path1.node, scope, (),
1456 |(), bcx, llval, ty| { zero_mem(bcx, llval, ty); bcx });
1462 Some(ref init_expr) => {
1463 // Optimize the "let x = expr" case. This just writes
1464 // the result of evaluating `expr` directly into the alloca
1465 // for `x`. Often the general path results in similar or the
1466 // same code post-optimization, but not always. In particular,
1467 // in unsafe code, you can have expressions like
1469 // let x = intrinsics::uninit();
1471 // In such cases, the more general path is unsafe, because
1472 // it assumes it is matching against a valid value.
1473 match simple_identifier(&*pat) {
1475 let var_scope = cleanup::var_scope(tcx, local.id);
1476 return mk_binding_alloca(
1477 bcx, pat.id, ident, var_scope, (),
1478 |(), bcx, v, _| expr::trans_into(bcx, &**init_expr,
1487 unpack_datum!(bcx, expr::trans_to_lvalue(bcx, &**init_expr, "let"));
1488 if bcx.sess().asm_comments() {
1489 add_comment(bcx, "creating zeroable ref llval");
1491 let var_scope = cleanup::var_scope(tcx, local.id);
1492 bind_irrefutable_pat(bcx, pat, init_datum.val, var_scope)
1495 create_dummy_locals(bcx, pat)
1500 /// Generates code for argument patterns like `fn foo(<pat>: T)`.
1501 /// Creates entries in the `lllocals` map for each of the bindings
1506 /// - `pat` is the argument pattern
1507 /// - `llval` is a pointer to the argument value (in other words,
1508 /// if the argument type is `T`, then `llval` is a `T*`). In some
1509 /// cases, this code may zero out the memory `llval` points at.
1510 pub fn store_arg<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
1512 arg: Datum<'tcx, Rvalue>,
1513 arg_scope: cleanup::ScopeId)
1514 -> Block<'blk, 'tcx> {
1515 let _icx = push_ctxt("match::store_arg");
1517 match simple_identifier(&*pat) {
1519 // Generate nicer LLVM for the common case of fn a pattern
1521 let arg_ty = node_id_type(bcx, pat.id);
1522 if type_of::arg_is_indirect(bcx.ccx(), arg_ty)
1523 && bcx.sess().opts.debuginfo != FullDebugInfo {
1524 // Don't copy an indirect argument to an alloca, the caller
1525 // already put it in a temporary alloca and gave it up, unless
1526 // we emit extra-debug-info, which requires local allocas :(.
1527 let arg_val = arg.add_clean(bcx.fcx, arg_scope);
1528 bcx.fcx.lllocals.borrow_mut()
1529 .insert(pat.id, Datum::new(arg_val, arg_ty, Lvalue));
1533 bcx, pat.id, ident, arg_scope, arg,
1534 |arg, bcx, llval, _| arg.store_to(bcx, llval))
1539 // General path. Copy out the values that are used in the
1541 let arg = unpack_datum!(
1542 bcx, arg.to_lvalue_datum_in_scope(bcx, "__arg", arg_scope));
1543 bind_irrefutable_pat(bcx, pat, arg.val, arg_scope)
1548 /// Generates code for the pattern binding in a `for` loop like
1549 /// `for <pat> in <expr> { ... }`.
1550 pub fn store_for_loop_binding<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
1553 body_scope: cleanup::ScopeId)
1554 -> Block<'blk, 'tcx> {
1555 let _icx = push_ctxt("match::store_for_loop_binding");
1557 if simple_identifier(&*pat).is_some() &&
1558 bcx.sess().opts.debuginfo != FullDebugInfo {
1559 // Generate nicer LLVM for the common case of a `for` loop pattern
1560 // like `for x in blahblah { ... }`.
1561 let binding_type = node_id_type(bcx, pat.id);
1562 bcx.fcx.lllocals.borrow_mut().insert(pat.id,
1569 // General path. Copy out the values that are used in the pattern.
1570 bind_irrefutable_pat(bcx, pat, llvalue, body_scope)
1573 fn mk_binding_alloca<'blk, 'tcx, A, F>(bcx: Block<'blk, 'tcx>,
1576 cleanup_scope: cleanup::ScopeId,
1579 -> Block<'blk, 'tcx> where
1580 F: FnOnce(A, Block<'blk, 'tcx>, ValueRef, Ty<'tcx>) -> Block<'blk, 'tcx>,
1582 let var_ty = node_id_type(bcx, p_id);
1584 // Allocate memory on stack for the binding.
1585 let llval = alloc_ty(bcx, var_ty, bcx.ident(*ident)[]);
1587 // Subtle: be sure that we *populate* the memory *before*
1588 // we schedule the cleanup.
1589 let bcx = populate(arg, bcx, llval, var_ty);
1590 bcx.fcx.schedule_lifetime_end(cleanup_scope, llval);
1591 bcx.fcx.schedule_drop_mem(cleanup_scope, llval, var_ty);
1593 // Now that memory is initialized and has cleanup scheduled,
1594 // create the datum and insert into the local variable map.
1595 let datum = Datum::new(llval, var_ty, Lvalue);
1596 bcx.fcx.lllocals.borrow_mut().insert(p_id, datum);
1600 /// A simple version of the pattern matching code that only handles
1601 /// irrefutable patterns. This is used in let/argument patterns,
1602 /// not in match statements. Unifying this code with the code above
1603 /// sounds nice, but in practice it produces very inefficient code,
1604 /// since the match code is so much more general. In most cases,
1605 /// LLVM is able to optimize the code, but it causes longer compile
1606 /// times and makes the generated code nigh impossible to read.
1609 /// - bcx: starting basic block context
1610 /// - pat: the irrefutable pattern being matched.
1611 /// - val: the value being matched -- must be an lvalue (by ref, with cleanup)
1612 fn bind_irrefutable_pat<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
1615 cleanup_scope: cleanup::ScopeId)
1616 -> Block<'blk, 'tcx> {
1617 debug!("bind_irrefutable_pat(bcx={}, pat={})",
1619 pat.repr(bcx.tcx()));
1621 if bcx.sess().asm_comments() {
1622 add_comment(bcx, format!("bind_irrefutable_pat(pat={})",
1623 pat.repr(bcx.tcx()))[]);
1626 let _indenter = indenter();
1628 let _icx = push_ctxt("match::bind_irrefutable_pat");
1630 let tcx = bcx.tcx();
1631 let ccx = bcx.ccx();
1633 ast::PatIdent(pat_binding_mode, ref path1, ref inner) => {
1634 if pat_is_binding(&tcx.def_map, &*pat) {
1635 // Allocate the stack slot where the value of this
1636 // binding will live and place it into the appropriate
1638 bcx = mk_binding_alloca(
1639 bcx, pat.id, &path1.node, cleanup_scope, (),
1640 |(), bcx, llval, ty| {
1641 match pat_binding_mode {
1642 ast::BindByValue(_) => {
1643 // By value binding: move the value that `val`
1644 // points at into the binding's stack slot.
1645 let d = Datum::new(val, ty, Lvalue);
1646 d.store_to(bcx, llval)
1649 ast::BindByRef(_) => {
1650 // By ref binding: the value of the variable
1651 // is the pointer `val` itself.
1652 Store(bcx, val, llval);
1659 for inner_pat in inner.iter() {
1660 bcx = bind_irrefutable_pat(bcx, &**inner_pat, val, cleanup_scope);
1663 ast::PatEnum(_, ref sub_pats) => {
1664 let opt_def = bcx.tcx().def_map.borrow().get(&pat.id).cloned();
1666 Some(def::DefVariant(enum_id, var_id, _)) => {
1667 let repr = adt::represent_node(bcx, pat.id);
1668 let vinfo = ty::enum_variant_with_id(ccx.tcx(),
1671 let args = extract_variant_args(bcx,
1675 for sub_pat in sub_pats.iter() {
1676 for (i, &argval) in args.vals.iter().enumerate() {
1677 bcx = bind_irrefutable_pat(bcx, &*sub_pat[i],
1678 argval, cleanup_scope);
1682 Some(def::DefStruct(..)) => {
1685 // This is a unit-like struct. Nothing to do here.
1687 Some(ref elems) => {
1688 // This is the tuple struct case.
1689 let repr = adt::represent_node(bcx, pat.id);
1690 for (i, elem) in elems.iter().enumerate() {
1691 let fldptr = adt::trans_field_ptr(bcx, &*repr,
1693 bcx = bind_irrefutable_pat(bcx, &**elem,
1694 fldptr, cleanup_scope);
1700 // Nothing to do here.
1704 ast::PatStruct(_, ref fields, _) => {
1705 let tcx = bcx.tcx();
1706 let pat_ty = node_id_type(bcx, pat.id);
1707 let pat_repr = adt::represent_type(bcx.ccx(), pat_ty);
1708 expr::with_field_tys(tcx, pat_ty, Some(pat.id), |discr, field_tys| {
1709 for f in fields.iter() {
1710 let ix = ty::field_idx_strict(tcx, f.node.ident.name, field_tys);
1711 let fldptr = adt::trans_field_ptr(bcx, &*pat_repr, val,
1713 bcx = bind_irrefutable_pat(bcx, &*f.node.pat, fldptr, cleanup_scope);
1717 ast::PatTup(ref elems) => {
1718 let repr = adt::represent_node(bcx, pat.id);
1719 for (i, elem) in elems.iter().enumerate() {
1720 let fldptr = adt::trans_field_ptr(bcx, &*repr, val, 0, i);
1721 bcx = bind_irrefutable_pat(bcx, &**elem, fldptr, cleanup_scope);
1724 ast::PatBox(ref inner) => {
1725 let llbox = Load(bcx, val);
1726 bcx = bind_irrefutable_pat(bcx, &**inner, llbox, cleanup_scope);
1728 ast::PatRegion(ref inner) => {
1729 let loaded_val = Load(bcx, val);
1730 bcx = bind_irrefutable_pat(bcx, &**inner, loaded_val, cleanup_scope);
1732 ast::PatVec(ref before, ref slice, ref after) => {
1733 let pat_ty = node_id_type(bcx, pat.id);
1734 let mut extracted = extract_vec_elems(bcx, pat_ty, before.len(), after.len(), val);
1737 extracted.vals.insert(
1739 bind_subslice_pat(bcx, pat.id, val, before.len(), after.len())
1746 .chain(slice.iter())
1747 .chain(after.iter())
1748 .zip(extracted.vals.into_iter())
1749 .fold(bcx, |bcx, (inner, elem)|
1750 bind_irrefutable_pat(bcx, &**inner, elem, cleanup_scope)
1753 ast::PatMac(..) => {
1754 bcx.sess().span_bug(pat.span, "unexpanded macro");
1756 ast::PatWild(_) | ast::PatLit(_) | ast::PatRange(_, _) => ()