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.
13 * # Compilation of match statements
15 * I will endeavor to explain the code as best I can. I have only a loose
16 * understanding of some parts of it.
20 * The basic state of the code is maintained in an array `m` of `Match`
21 * objects. Each `Match` describes some list of patterns, all of which must
22 * match against the current list of values. If those patterns match, then
23 * the arm listed in the match is the correct arm. A given arm may have
24 * multiple corresponding match entries, one for each alternative that
25 * remains. As we proceed these sets of matches are adjusted by the various
26 * `enter_XXX()` functions, each of which adjusts the set of options given
27 * some information about the value which has been matched.
29 * So, initially, there is one value and N matches, each of which have one
30 * constituent pattern. N here is usually the number of arms but may be
31 * greater, if some arms have multiple alternatives. For example, here:
33 * enum Foo { A, B(int), C(uint, uint) }
41 * The value would be `foo`. There would be four matches, each of which
42 * contains one pattern (and, in one case, a guard). We could collect the
43 * various options and then compile the code for the case where `foo` is an
44 * `A`, a `B`, and a `C`. When we generate the code for `C`, we would (1)
45 * drop the two matches that do not match a `C` and (2) expand the other two
46 * into two patterns each. In the first case, the two patterns would be `1u`
47 * and `2`, and the in the second case the _ pattern would be expanded into
48 * `_` and `_`. The two values are of course the arguments to `C`.
50 * Here is a quick guide to the various functions:
52 * - `compile_submatch()`: The main workhouse. It takes a list of values and
53 * a list of matches and finds the various possibilities that could occur.
55 * - `enter_XXX()`: modifies the list of matches based on some information
56 * about the value that has been matched. For example,
57 * `enter_rec_or_struct()` adjusts the values given that a record or struct
58 * has been matched. This is an infallible pattern, so *all* of the matches
59 * must be either wildcards or record/struct patterns. `enter_opt()`
60 * handles the fallible cases, and it is correspondingly more complex.
64 * We store information about the bound variables for each arm as part of the
65 * per-arm `ArmData` struct. There is a mapping from identifiers to
66 * `BindingInfo` structs. These structs contain the mode/id/type of the
67 * binding, but they also contain up to two LLVM values, called `llmatch` and
68 * `llbinding` respectively (the `llbinding`, as will be described shortly, is
69 * optional and only present for by-value bindings---therefore it is bundled
70 * up as part of the `TransBindingMode` type). Both point at allocas.
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 * In addition, for each by-value binding (copy or move), we will create a
87 * second alloca (`llbinding`) that will hold the final value. In this
88 * example, that means that `d` would have this second alloca of type `D` (and
89 * hence `llbinding` has type `D*`).
91 * Once a pattern is completely matched, and assuming that there is no guard
92 * pattern, we will branch to a block that leads to the body itself. For any
93 * by-value bindings, this block will first load the ptr from `llmatch` (the
94 * one of type `D*`) and copy/move the value into `llbinding` (the one of type
95 * `D`). The second alloca then becomes the value of the local variable. For
96 * by ref bindings, the value of the local variable is simply the first
99 * So, for the example above, we would generate a setup kind of like this:
105 * +-------------------------------------------+
106 * | llmatch_c = (addr of first half of tuple) |
107 * | llmatch_d = (addr of first half of tuple) |
108 * +-------------------------------------------+
110 * +--------------------------------------+
111 * | *llbinding_d = **llmatch_dlbinding_d |
112 * +--------------------------------------+
114 * If there is a guard, the situation is slightly different, because we must
115 * execute the guard code. Moreover, we need to do so once for each of the
116 * alternatives that lead to the arm, because if the guard fails, they may
117 * have different points from which to continue the search. Therefore, in that
118 * case, we generate code that looks more like:
124 * +-------------------------------------------+
125 * | llmatch_c = (addr of first half of tuple) |
126 * | llmatch_d = (addr of first half of tuple) |
127 * +-------------------------------------------+
129 * +-------------------------------------------------+
130 * | *llbinding_d = **llmatch_dlbinding_d |
131 * | check condition |
132 * | if false { free *llbinding_d, goto next case } |
133 * | if true { goto body } |
134 * +-------------------------------------------------+
136 * The handling for the cleanups is a bit... sensitive. Basically, the body
137 * is the one that invokes `add_clean()` for each binding. During the guard
138 * evaluation, we add temporary cleanups and revoke them after the guard is
139 * evaluated (it could fail, after all). Presuming the guard fails, we drop
140 * the various values we copied explicitly. Note that guards and moves are
141 * just plain incompatible.
143 * Some relevant helper functions that manage bindings:
144 * - `create_bindings_map()`
145 * - `store_non_ref_bindings()`
146 * - `insert_lllocals()`
149 * ## Notes on vector pattern matching.
151 * Vector pattern matching is surprisingly tricky. The problem is that
152 * the structure of the vector isn't fully known, and slice matches
153 * can be done on subparts of it.
155 * The way that vector pattern matches are dealt with, then, is as
156 * follows. First, we make the actual condition associated with a
157 * vector pattern simply a vector length comparison. So the pattern
158 * [1, .. x] gets the condition "vec len >= 1", and the pattern
159 * [.. x] gets the condition "vec len >= 0". The problem here is that
160 * having the condition "vec len >= 1" hold clearly does not mean that
161 * only a pattern that has exactly that condition will match. This
162 * means that it may well be the case that a condition holds, but none
163 * of the patterns matching that condition match; to deal with this,
164 * when doing vector length matches, we have match failures proceed to
165 * the next condition to check.
167 * There are a couple more subtleties to deal with. While the "actual"
168 * condition associated with vector length tests is simply a test on
169 * the vector length, the actual vec_len Opt entry contains more
170 * information used to restrict which matches are associated with it.
171 * So that all matches in a submatch are matching against the same
172 * values from inside the vector, they are split up by how many
173 * elements they match at the front and at the back of the vector. In
174 * order to make sure that arms are properly checked in order, even
175 * with the overmatching conditions, each vec_len Opt entry is
176 * associated with a range of matches.
177 * Consider the following:
181 * [1, 2, 2, .. _] => 1,
182 * [1, 2, 3, .. _] => 2,
186 * The proper arm to match is arm 2, but arms 0 and 3 both have the
187 * condition "len >= 2". If arm 3 was lumped in with arm 0, then the
188 * wrong branch would be taken. Instead, vec_len Opts are associated
189 * with a contiguous range of matches that have the same "shape".
190 * This is sort of ugly and requires a bunch of special handling of
195 #[allow(non_camel_case_types)];
198 use lib::llvm::{llvm, ValueRef, BasicBlockRef};
199 use middle::const_eval;
200 use middle::borrowck::root_map_key;
201 use middle::lang_items::{UniqStrEqFnLangItem, StrEqFnLangItem};
202 use middle::pat_util::*;
203 use middle::resolve::DefMap;
204 use middle::trans::adt;
205 use middle::trans::base::*;
206 use middle::trans::build::*;
207 use middle::trans::callee;
208 use middle::trans::cleanup;
209 use middle::trans::cleanup::CleanupMethods;
210 use middle::trans::common::*;
211 use middle::trans::consts;
212 use middle::trans::controlflow;
213 use middle::trans::datum;
214 use middle::trans::datum::*;
215 use middle::trans::expr::Dest;
216 use middle::trans::expr;
217 use middle::trans::glue;
218 use middle::trans::tvec;
219 use middle::trans::type_of;
220 use middle::trans::debuginfo;
222 use util::common::indenter;
223 use util::ppaux::{Repr, vec_map_to_str};
226 use collections::HashMap;
229 use syntax::ast::Ident;
230 use syntax::ast_util::path_to_ident;
231 use syntax::ast_util;
232 use syntax::codemap::{Span, DUMMY_SP};
233 use syntax::parse::token::InternedString;
235 // An option identifying a literal: either a unit-like struct or an
238 UnitLikeStructLit(ast::NodeId), // the node ID of the pattern
240 ConstLit(ast::DefId), // the def ID of the constant
246 vec_len_ge(/* length of prefix */uint)
249 // An option identifying a branch (either a literal, an enum variant or a
253 var(ty::Disr, @adt::Repr),
254 range(@ast::Expr, @ast::Expr),
255 vec_len(/* length */ uint, VecLenOpt, /*range of matches*/(uint, uint))
258 fn opt_eq(tcx: ty::ctxt, a: &Opt, b: &Opt) -> bool {
260 (&lit(a), &lit(b)) => {
262 (UnitLikeStructLit(a), UnitLikeStructLit(b)) => a == b,
266 ExprLit(existing_a_expr) => a_expr = existing_a_expr,
267 ConstLit(a_const) => {
268 let e = const_eval::lookup_const_by_id(tcx, a_const);
271 UnitLikeStructLit(_) => {
272 fail!("UnitLikeStructLit should have been handled \
279 ExprLit(existing_b_expr) => b_expr = existing_b_expr,
280 ConstLit(b_const) => {
281 let e = const_eval::lookup_const_by_id(tcx, b_const);
284 UnitLikeStructLit(_) => {
285 fail!("UnitLikeStructLit should have been handled \
290 match const_eval::compare_lit_exprs(tcx, a_expr, b_expr) {
291 Some(val1) => val1 == 0,
292 None => fail!("compare_list_exprs: type mismatch"),
297 (&range(a1, a2), &range(b1, b2)) => {
298 let m1 = const_eval::compare_lit_exprs(tcx, a1, b1);
299 let m2 = const_eval::compare_lit_exprs(tcx, a2, b2);
301 (Some(val1), Some(val2)) => (val1 == 0 && val2 == 0),
302 _ => fail!("compare_list_exprs: type mismatch"),
305 (&var(a, _), &var(b, _)) => a == b,
306 (&vec_len(a1, a2, _), &vec_len(b1, b2, _)) =>
307 a1 == b1 && a2 == b2,
312 pub enum opt_result<'a> {
313 single_result(Result<'a>),
314 lower_bound(Result<'a>),
315 range_result(Result<'a>, Result<'a>),
318 fn trans_opt<'a>(bcx: &'a Block<'a>, o: &Opt) -> opt_result<'a> {
319 let _icx = push_ctxt("match::trans_opt");
323 lit(ExprLit(lit_expr)) => {
324 let lit_datum = unpack_datum!(bcx, expr::trans(bcx, lit_expr));
325 let lit_datum = lit_datum.assert_rvalue(bcx); // literals are rvalues
326 let lit_datum = unpack_datum!(bcx, lit_datum.to_appropriate_datum(bcx));
327 return single_result(rslt(bcx, lit_datum.val));
329 lit(UnitLikeStructLit(pat_id)) => {
330 let struct_ty = ty::node_id_to_type(bcx.tcx(), pat_id);
331 let datum = datum::rvalue_scratch_datum(bcx, struct_ty, "");
332 return single_result(rslt(bcx, datum.val));
334 lit(ConstLit(lit_id)) => {
335 let (llval, _) = consts::get_const_val(bcx.ccx(), lit_id);
336 return single_result(rslt(bcx, llval));
338 var(disr_val, repr) => {
339 return adt::trans_case(bcx, repr, disr_val);
342 let (l1, _) = consts::const_expr(ccx, l1, true);
343 let (l2, _) = consts::const_expr(ccx, l2, true);
344 return range_result(rslt(bcx, l1), rslt(bcx, l2));
346 vec_len(n, vec_len_eq, _) => {
347 return single_result(rslt(bcx, C_int(ccx, n as int)));
349 vec_len(n, vec_len_ge(_), _) => {
350 return lower_bound(rslt(bcx, C_int(ccx, n as int)));
355 fn variant_opt(bcx: &Block, pat_id: ast::NodeId) -> Opt {
357 let def_map = ccx.tcx.def_map.borrow();
358 match def_map.get().get_copy(&pat_id) {
359 ast::DefVariant(enum_id, var_id, _) => {
360 let variants = ty::enum_variants(ccx.tcx, enum_id);
361 for v in (*variants).iter() {
363 return var(v.disr_val,
364 adt::represent_node(bcx, pat_id))
370 ast::DefStruct(_) => {
371 return lit(UnitLikeStructLit(pat_id));
374 ccx.sess.bug("non-variant or struct in variant_opt()");
380 enum TransBindingMode {
381 TrByValue(/*llbinding:*/ ValueRef),
386 * Information about a pattern binding:
387 * - `llmatch` is a pointer to a stack slot. The stack slot contains a
388 * pointer into the value being matched. Hence, llmatch has type `T**`
389 * where `T` is the value being matched.
390 * - `trmode` is the trans binding mode
391 * - `id` is the node id of the binding
392 * - `ty` is the Rust type of the binding */
396 trmode: TransBindingMode,
402 type BindingsMap = HashMap<Ident, BindingInfo>;
404 struct ArmData<'a,'b> {
405 bodycx: &'b Block<'b>,
407 bindings_map: @BindingsMap
410 // FIXME #11820: method resolution is unreliable with &
411 impl<'a,'b> Clone for ArmData<'a, 'b> {
412 fn clone(&self) -> ArmData<'a, 'b> { *self }
417 * If all `pats` are matched then arm `data` will be executed.
418 * As we proceed `bound_ptrs` are filled with pointers to values to be bound,
419 * these pointers are stored in llmatch variables just before executing `data` arm.
422 struct Match<'a,'b> {
424 data: ArmData<'a,'b>,
425 bound_ptrs: ~[(Ident, ValueRef)]
428 impl<'a,'b> Repr for Match<'a,'b> {
429 fn repr(&self, tcx: ty::ctxt) -> ~str {
430 if tcx.sess.verbose() {
431 // for many programs, this just take too long to serialize
434 format!("{} pats", self.pats.len())
439 fn has_nested_bindings(m: &[Match], col: uint) -> bool {
441 match br.pats[col].node {
442 ast::PatIdent(_, _, Some(_)) => return true,
449 fn expand_nested_bindings<'r,'b>(
455 debug!("expand_nested_bindings(bcx={}, m={}, col={}, val={})",
459 bcx.val_to_str(val));
460 let _indenter = indenter();
463 match br.pats[col].node {
464 ast::PatIdent(_, ref path, Some(inner)) => {
465 let pats = vec::append(
466 br.pats.slice(0u, col).to_owned(),
467 vec::append(~[inner],
468 br.pats.slice(col + 1u,
471 let mut res = Match {
473 data: br.data.clone(),
474 bound_ptrs: br.bound_ptrs.clone()
476 res.bound_ptrs.push((path_to_ident(path), val));
484 fn assert_is_binding_or_wild(bcx: &Block, p: @ast::Pat) {
485 if !pat_is_binding_or_wild(bcx.tcx().def_map, p) {
488 format!("expected an identifier pattern but found p: {}",
493 type enter_pat<'a> = 'a |@ast::Pat| -> Option<~[@ast::Pat]>;
495 fn enter_match<'r,'b>(
503 debug!("enter_match(bcx={}, m={}, col={}, val={})",
507 bcx.val_to_str(val));
508 let _indenter = indenter();
510 let mut result = ~[];
512 match e(br.pats[col]) {
516 vec::append(sub, br.pats.slice(0u, col)),
517 br.pats.slice(col + 1u, br.pats.len()));
519 let this = br.pats[col];
520 let mut bound_ptrs = br.bound_ptrs.clone();
522 ast::PatIdent(_, ref path, None) => {
523 if pat_is_binding(dm, this) {
524 bound_ptrs.push((path_to_ident(path), val));
532 data: br.data.clone(),
533 bound_ptrs: bound_ptrs
540 debug!("result={}", result.repr(bcx.tcx()));
545 fn enter_default<'r,'b>(
551 chk: &FailureHandler)
553 debug!("enter_default(bcx={}, m={}, col={}, val={})",
557 bcx.val_to_str(val));
558 let _indenter = indenter();
560 // Collect all of the matches that can match against anything.
561 let matches = enter_match(bcx, dm, m, col, val, |p| {
563 ast::PatWild | ast::PatWildMulti | ast::PatTup(_) => Some(~[]),
564 ast::PatIdent(_, _, None) if pat_is_binding(dm, p) => Some(~[]),
569 // Ok, now, this is pretty subtle. A "default" match is a match
570 // that needs to be considered if none of the actual checks on the
571 // value being considered succeed. The subtlety lies in that sometimes
572 // identifier/wildcard matches are *not* default matches. Consider:
573 // "match x { _ if something => foo, true => bar, false => baz }".
574 // There is a wildcard match, but it is *not* a default case. The boolean
575 // case on the value being considered is exhaustive. If the case is
576 // exhaustive, then there are no defaults.
578 // We detect whether the case is exhaustive in the following
579 // somewhat kludgy way: if the last wildcard/binding match has a
580 // guard, then by non-redundancy, we know that there aren't any
581 // non guarded matches, and thus by exhaustiveness, we know that
582 // we don't need any default cases. If the check *isn't* nonexhaustive
583 // (because chk is Some), then we need the defaults anyways.
584 let is_exhaustive = match matches.last() {
585 Some(m) if m.data.arm.guard.is_some() && chk.is_infallible() => true,
589 if is_exhaustive { ~[] } else { matches }
592 // <pcwalton> nmatsakis: what does enter_opt do?
593 // <pcwalton> in trans/match
594 // <pcwalton> trans/match.rs is like stumbling around in a dark cave
595 // <nmatsakis> pcwalton: the enter family of functions adjust the set of
596 // patterns as needed
597 // <nmatsakis> yeah, at some point I kind of achieved some level of
599 // <nmatsakis> anyhow, they adjust the patterns given that something of that
600 // kind has been found
601 // <nmatsakis> pcwalton: ok, right, so enter_XXX() adjusts the patterns, as I
603 // <nmatsakis> enter_match() kind of embodies the generic code
604 // <nmatsakis> it is provided with a function that tests each pattern to see
605 // if it might possibly apply and so forth
606 // <nmatsakis> so, if you have a pattern like {a: _, b: _, _} and one like _
607 // <nmatsakis> then _ would be expanded to (_, _)
608 // <nmatsakis> one spot for each of the sub-patterns
609 // <nmatsakis> enter_opt() is one of the more complex; it covers the fallible
611 // <nmatsakis> enter_rec_or_struct() or enter_tuple() are simpler, since they
612 // are infallible patterns
613 // <nmatsakis> so all patterns must either be records (resp. tuples) or
624 debug!("enter_opt(bcx={}, m={}, opt={:?}, col={}, val={})",
629 bcx.val_to_str(val));
630 let _indenter = indenter();
633 let dummy = @ast::Pat {id: 0, node: ast::PatWild, span: DUMMY_SP};
635 enter_match(bcx, tcx.def_map, m, col, val, |p| {
636 let answer = match p.node {
638 ast::PatIdent(_, _, None) if pat_is_const(tcx.def_map, p) => {
640 let def_map = tcx.def_map.borrow();
641 def_map.get().get_copy(&p.id)
643 let const_def_id = ast_util::def_id_of_def(const_def);
644 if opt_eq(tcx, &lit(ConstLit(const_def_id)), opt) {
650 ast::PatEnum(_, ref subpats) => {
651 if opt_eq(tcx, &variant_opt(bcx, p.id), opt) {
652 // FIXME: Must we clone?
654 None => Some(vec::from_elem(variant_size, dummy)),
655 _ => (*subpats).clone(),
661 ast::PatIdent(_, _, None)
662 if pat_is_variant_or_struct(tcx.def_map, p) => {
663 if opt_eq(tcx, &variant_opt(bcx, p.id), opt) {
670 if opt_eq(tcx, &lit(ExprLit(l)), opt) {Some(~[])} else {None}
672 ast::PatRange(l1, l2) => {
673 if opt_eq(tcx, &range(l1, l2), opt) {Some(~[])} else {None}
675 ast::PatStruct(_, ref field_pats, _) => {
676 if opt_eq(tcx, &variant_opt(bcx, p.id), opt) {
677 // Look up the struct variant ID.
680 let def_map = tcx.def_map.borrow();
681 def_map.get().get_copy(&p.id)
684 ast::DefVariant(_, found_struct_id, _) => {
685 struct_id = found_struct_id;
688 tcx.sess.span_bug(p.span, "expected enum variant def");
692 // Reorder the patterns into the same order they were
693 // specified in the struct definition. Also fill in
694 // unspecified fields with dummy.
695 let mut reordered_patterns = ~[];
696 let r = ty::lookup_struct_fields(tcx, struct_id);
697 for field in r.iter() {
698 match field_pats.iter().find(|p| p.ident.name
700 None => reordered_patterns.push(dummy),
701 Some(fp) => reordered_patterns.push(fp.pat)
704 Some(reordered_patterns)
709 ast::PatVec(ref before, slice, ref after) => {
710 let (lo, hi) = match *opt {
711 vec_len(_, _, (lo, hi)) => (lo, hi),
712 _ => tcx.sess.span_bug(p.span,
713 "vec pattern but not vec opt")
717 Some(slice) if i >= lo && i <= hi => {
718 let n = before.len() + after.len();
719 let this_opt = vec_len(n, vec_len_ge(before.len()),
721 if opt_eq(tcx, &this_opt, opt) {
722 Some(vec::append_one((*before).clone(), slice) +
728 None if i >= lo && i <= hi => {
729 let n = before.len();
730 if opt_eq(tcx, &vec_len(n, vec_len_eq, (lo,hi)), opt) {
731 Some((*before).clone())
740 assert_is_binding_or_wild(bcx, p);
741 // In most cases, a binding/wildcard match be
742 // considered to match against any Opt. However, when
743 // doing vector pattern matching, submatches are
744 // considered even if the eventual match might be from
745 // a different submatch. Thus, when a submatch fails
746 // when doing a vector match, we proceed to the next
747 // submatch. Thus, including a default match would
748 // cause the default match to fire spuriously.
751 _ => Some(vec::from_elem(variant_size, dummy))
760 fn enter_rec_or_struct<'r,'b>(
765 fields: &[ast::Ident],
768 debug!("enter_rec_or_struct(bcx={}, m={}, col={}, val={})",
772 bcx.val_to_str(val));
773 let _indenter = indenter();
775 let dummy = @ast::Pat {id: 0, node: ast::PatWild, span: DUMMY_SP};
776 enter_match(bcx, dm, m, col, val, |p| {
778 ast::PatStruct(_, ref fpats, _) => {
780 for fname in fields.iter() {
781 match fpats.iter().find(|p| p.ident.name == fname.name) {
782 None => pats.push(dummy),
783 Some(pat) => pats.push(pat.pat)
789 assert_is_binding_or_wild(bcx, p);
790 Some(vec::from_elem(fields.len(), dummy))
804 debug!("enter_tup(bcx={}, m={}, col={}, val={})",
808 bcx.val_to_str(val));
809 let _indenter = indenter();
811 let dummy = @ast::Pat {id: 0, node: ast::PatWild, span: DUMMY_SP};
812 enter_match(bcx, dm, m, col, val, |p| {
814 ast::PatTup(ref elts) => Some((*elts).clone()),
816 assert_is_binding_or_wild(bcx, p);
817 Some(vec::from_elem(n_elts, dummy))
823 fn enter_tuple_struct<'r,'b>(
831 debug!("enter_tuple_struct(bcx={}, m={}, col={}, val={})",
835 bcx.val_to_str(val));
836 let _indenter = indenter();
838 let dummy = @ast::Pat {id: 0, node: ast::PatWild, span: DUMMY_SP};
839 enter_match(bcx, dm, m, col, val, |p| {
841 ast::PatEnum(_, Some(ref elts)) => Some((*elts).clone()),
843 assert_is_binding_or_wild(bcx, p);
844 Some(vec::from_elem(n_elts, dummy))
850 fn enter_uniq<'r,'b>(
857 debug!("enter_uniq(bcx={}, m={}, col={}, val={})",
861 bcx.val_to_str(val));
862 let _indenter = indenter();
864 let dummy = @ast::Pat {id: 0, node: ast::PatWild, span: DUMMY_SP};
865 enter_match(bcx, dm, m, col, val, |p| {
867 ast::PatUniq(sub) => {
871 assert_is_binding_or_wild(bcx, p);
886 debug!("enter_region(bcx={}, m={}, col={}, val={})",
890 bcx.val_to_str(val));
891 let _indenter = indenter();
893 let dummy = @ast::Pat { id: 0, node: ast::PatWild, span: DUMMY_SP };
894 enter_match(bcx, dm, m, col, val, |p| {
896 ast::PatRegion(sub) => {
900 assert_is_binding_or_wild(bcx, p);
907 // Returns the options in one column of matches. An option is something that
908 // needs to be conditionally matched at runtime; for example, the discriminant
909 // on a set of enum variants or a literal.
910 fn get_options(bcx: &Block, m: &[Match], col: uint) -> ~[Opt] {
912 fn add_to_set(tcx: ty::ctxt, set: &mut ~[Opt], val: Opt) {
913 if set.iter().any(|l| opt_eq(tcx, l, &val)) {return;}
916 // Vector comparisions are special in that since the actual
917 // conditions over-match, we need to be careful about them. This
918 // means that in order to properly handle things in order, we need
919 // to not always merge conditions.
920 fn add_veclen_to_set(set: &mut ~[Opt], i: uint,
921 len: uint, vlo: VecLenOpt) {
923 // If the last condition in the list matches the one we want
924 // to add, then extend its range. Otherwise, make a new
925 // vec_len with a range just covering the new entry.
926 Some(&vec_len(len2, vlo2, (start, end)))
927 if len == len2 && vlo == vlo2 =>
928 set[set.len() - 1] = vec_len(len, vlo, (start, end+1)),
929 _ => set.push(vec_len(len, vlo, (i, i)))
934 for (i, br) in m.iter().enumerate() {
935 let cur = br.pats[col];
938 add_to_set(ccx.tcx, &mut found, lit(ExprLit(l)));
940 ast::PatIdent(..) => {
941 // This is one of: an enum variant, a unit-like struct, or a
944 let def_map = ccx.tcx.def_map.borrow();
945 def_map.get().find_copy(&cur.id)
948 Some(ast::DefVariant(..)) => {
949 add_to_set(ccx.tcx, &mut found,
950 variant_opt(bcx, cur.id));
952 Some(ast::DefStruct(..)) => {
953 add_to_set(ccx.tcx, &mut found,
954 lit(UnitLikeStructLit(cur.id)));
956 Some(ast::DefStatic(const_did, false)) => {
957 add_to_set(ccx.tcx, &mut found,
958 lit(ConstLit(const_did)));
963 ast::PatEnum(..) | ast::PatStruct(..) => {
964 // This could be one of: a tuple-like enum variant, a
965 // struct-like enum variant, or a struct.
967 let def_map = ccx.tcx.def_map.borrow();
968 def_map.get().find_copy(&cur.id)
971 Some(ast::DefFn(..)) |
972 Some(ast::DefVariant(..)) => {
973 add_to_set(ccx.tcx, &mut found,
974 variant_opt(bcx, cur.id));
976 Some(ast::DefStatic(const_did, false)) => {
977 add_to_set(ccx.tcx, &mut found,
978 lit(ConstLit(const_did)));
983 ast::PatRange(l1, l2) => {
984 add_to_set(ccx.tcx, &mut found, range(l1, l2));
986 ast::PatVec(ref before, slice, ref after) => {
987 let (len, vec_opt) = match slice {
988 None => (before.len(), vec_len_eq),
989 Some(_) => (before.len() + after.len(),
990 vec_len_ge(before.len()))
992 add_veclen_to_set(&mut found, i, len, vec_opt);
1000 struct ExtractedBlock<'a> {
1005 fn extract_variant_args<'a>(
1010 -> ExtractedBlock<'a> {
1011 let _icx = push_ctxt("match::extract_variant_args");
1012 let args = vec::from_fn(adt::num_args(repr, disr_val), |i| {
1013 adt::trans_field_ptr(bcx, repr, val, disr_val, i)
1016 ExtractedBlock { vals: args, bcx: bcx }
1019 fn match_datum(bcx: &Block,
1021 pat_id: ast::NodeId)
1024 * Helper for converting from the ValueRef that we pass around in
1025 * the match code, which is always an lvalue, into a Datum. Eventually
1026 * we should just pass around a Datum and be done with it.
1029 let ty = node_id_type(bcx, pat_id);
1030 Datum(val, ty, Lvalue)
1034 fn extract_vec_elems<'a>(
1036 pat_id: ast::NodeId,
1038 slice: Option<uint>,
1041 -> ExtractedBlock<'a> {
1042 let _icx = push_ctxt("match::extract_vec_elems");
1043 let vec_datum = match_datum(bcx, val, pat_id);
1044 let (base, len) = vec_datum.get_vec_base_and_len(bcx);
1045 let vt = tvec::vec_types(bcx, node_id_type(bcx, pat_id));
1047 let mut elems = vec::from_fn(elem_count, |i| {
1049 None => GEPi(bcx, base, [i]),
1050 Some(n) if i < n => GEPi(bcx, base, [i]),
1051 Some(n) if i > n => {
1052 InBoundsGEP(bcx, base, [
1054 C_int(bcx.ccx(), (elem_count - i) as int))])
1056 _ => unsafe { llvm::LLVMGetUndef(vt.llunit_ty.to_ref()) }
1059 if slice.is_some() {
1060 let n = slice.unwrap();
1061 let slice_byte_offset = Mul(bcx, vt.llunit_size, C_uint(bcx.ccx(), n));
1062 let slice_begin = tvec::pointer_add_byte(bcx, base, slice_byte_offset);
1063 let slice_len_offset = C_uint(bcx.ccx(), elem_count - 1u);
1064 let slice_len = Sub(bcx, len, slice_len_offset);
1065 let slice_ty = ty::mk_vec(bcx.tcx(),
1066 ty::mt {ty: vt.unit_ty, mutbl: ast::MutImmutable},
1067 ty::vstore_slice(ty::ReStatic)
1069 let scratch = rvalue_scratch_datum(bcx, slice_ty, "");
1070 Store(bcx, slice_begin,
1071 GEPi(bcx, scratch.val, [0u, abi::slice_elt_base]));
1072 Store(bcx, slice_len, GEPi(bcx, scratch.val, [0u, abi::slice_elt_len]));
1073 elems[n] = scratch.val;
1076 ExtractedBlock { vals: elems, bcx: bcx }
1079 /// Checks every pattern in `m` at `col` column.
1080 /// If there are a struct pattern among them function
1081 /// returns list of all fields that are matched in these patterns.
1082 /// Function returns None if there is no struct pattern.
1083 /// Function doesn't collect fields from struct-like enum variants.
1084 /// Function can return empty list if there is only wildcard struct pattern.
1085 fn collect_record_or_struct_fields<'a>(
1089 -> Option<~[ast::Ident]> {
1090 let mut fields: ~[ast::Ident] = ~[];
1091 let mut found = false;
1092 for br in m.iter() {
1093 match br.pats[col].node {
1094 ast::PatStruct(_, ref fs, _) => {
1095 match ty::get(node_id_type(bcx, br.pats[col].id)).sty {
1096 ty::ty_struct(..) => {
1097 extend(&mut fields, *fs);
1107 return Some(fields);
1112 fn extend(idents: &mut ~[ast::Ident], field_pats: &[ast::FieldPat]) {
1113 for field_pat in field_pats.iter() {
1114 let field_ident = field_pat.ident;
1115 if !idents.iter().any(|x| x.name == field_ident.name) {
1116 idents.push(field_ident);
1122 fn pats_require_rooting(bcx: &Block, m: &[Match], col: uint) -> bool {
1124 let pat_id = br.pats[col].id;
1125 let key = root_map_key {id: pat_id, derefs: 0u };
1126 let root_map = bcx.ccx().maps.root_map.borrow();
1127 root_map.get().contains_key(&key)
1131 // Macro for deciding whether any of the remaining matches fit a given kind of
1132 // pattern. Note that, because the macro is well-typed, either ALL of the
1133 // matches should fit that sort of pattern or NONE (however, some of the
1134 // matches may be wildcards like _ or identifiers).
1135 macro_rules! any_pat (
1136 ($m:expr, $pattern:pat) => (
1137 ($m).iter().any(|br| {
1138 match br.pats[col].node {
1146 fn any_uniq_pat(m: &[Match], col: uint) -> bool {
1147 any_pat!(m, ast::PatUniq(_))
1150 fn any_region_pat(m: &[Match], col: uint) -> bool {
1151 any_pat!(m, ast::PatRegion(_))
1154 fn any_tup_pat(m: &[Match], col: uint) -> bool {
1155 any_pat!(m, ast::PatTup(_))
1158 fn any_tuple_struct_pat(bcx: &Block, m: &[Match], col: uint) -> bool {
1160 let pat = br.pats[col];
1162 ast::PatEnum(_, Some(_)) => {
1163 let def_map = bcx.tcx().def_map.borrow();
1164 match def_map.get().find(&pat.id) {
1165 Some(&ast::DefFn(..)) |
1166 Some(&ast::DefStruct(..)) => true,
1175 struct DynamicFailureHandler<'a> {
1178 msg: InternedString,
1179 finished: @Cell<Option<BasicBlockRef>>,
1182 impl<'a> DynamicFailureHandler<'a> {
1183 fn handle_fail(&self) -> BasicBlockRef {
1184 match self.finished.get() {
1185 Some(bb) => return bb,
1189 let fcx = self.bcx.fcx;
1190 let fail_cx = fcx.new_block(false, "case_fallthrough", None);
1191 controlflow::trans_fail(fail_cx, Some(self.sp), self.msg.clone());
1192 self.finished.set(Some(fail_cx.llbb));
1197 /// What to do when the pattern match fails.
1198 enum FailureHandler<'a> {
1200 JumpToBasicBlock(BasicBlockRef),
1201 DynamicFailureHandlerClass(~DynamicFailureHandler<'a>),
1204 impl<'a> FailureHandler<'a> {
1205 fn is_infallible(&self) -> bool {
1212 fn is_fallible(&self) -> bool {
1213 !self.is_infallible()
1216 fn handle_fail(&self) -> BasicBlockRef {
1219 fail!("attempted to fail in infallible failure handler!")
1221 JumpToBasicBlock(basic_block) => basic_block,
1222 DynamicFailureHandlerClass(ref dynamic_failure_handler) => {
1223 dynamic_failure_handler.handle_fail()
1229 fn pick_col(m: &[Match]) -> uint {
1230 fn score(p: &ast::Pat) -> uint {
1232 ast::PatLit(_) | ast::PatEnum(_, _) | ast::PatRange(_, _) => 1u,
1233 ast::PatIdent(_, _, Some(p)) => score(p),
1237 let mut scores = vec::from_elem(m[0].pats.len(), 0u);
1238 for br in m.iter() {
1239 for (i, p) in br.pats.iter().enumerate() {
1240 scores[i] += score(*p);
1243 let mut max_score = 0u;
1244 let mut best_col = 0u;
1245 for (i, score) in scores.iter().enumerate() {
1248 // Irrefutable columns always go first, they'd only be duplicated in
1250 if score == 0u { return i; }
1251 // If no irrefutable ones are found, we pick the one with the biggest
1252 // branching factor.
1253 if score > max_score { max_score = score; best_col = i; }
1259 pub enum branch_kind { no_branch, single, switch, compare, compare_vec_len, }
1261 // Compiles a comparison between two things.
1263 // NB: This must produce an i1, not a Rust bool (i8).
1264 fn compare_values<'a>(
1270 let _icx = push_ctxt("compare_values");
1271 if ty::type_is_scalar(rhs_t) {
1272 let rs = compare_scalar_types(cx, lhs, rhs, rhs_t, ast::BiEq);
1273 return rslt(rs.bcx, rs.val);
1276 match ty::get(rhs_t).sty {
1277 ty::ty_str(ty::vstore_uniq) => {
1278 let scratch_lhs = alloca(cx, val_ty(lhs), "__lhs");
1279 Store(cx, lhs, scratch_lhs);
1280 let scratch_rhs = alloca(cx, val_ty(rhs), "__rhs");
1281 Store(cx, rhs, scratch_rhs);
1282 let did = langcall(cx, None,
1283 format!("comparison of `{}`", cx.ty_to_str(rhs_t)),
1284 UniqStrEqFnLangItem);
1285 let result = callee::trans_lang_call(cx, did, [scratch_lhs, scratch_rhs], None);
1288 val: bool_to_i1(result.bcx, result.val)
1292 let did = langcall(cx, None,
1293 format!("comparison of `{}`", cx.ty_to_str(rhs_t)),
1295 let result = callee::trans_lang_call(cx, did, [lhs, rhs], None);
1298 val: bool_to_i1(result.bcx, result.val)
1302 cx.tcx().sess.bug("only scalars and strings supported in \
1308 fn store_non_ref_bindings<'a>(
1310 bindings_map: &BindingsMap,
1311 opt_cleanup_scope: Option<cleanup::ScopeId>)
1315 * For each copy/move binding, copy the value from the value being
1316 * matched into its final home. This code executes once one of
1317 * the patterns for a given arm has completely matched. It adds
1318 * cleanups to the `opt_cleanup_scope`, if one is provided.
1323 for (_, &binding_info) in bindings_map.iter() {
1324 match binding_info.trmode {
1325 TrByValue(lldest) => {
1326 let llval = Load(bcx, binding_info.llmatch); // get a T*
1327 let datum = Datum(llval, binding_info.ty, Lvalue);
1328 bcx = datum.store_to(bcx, lldest);
1330 match opt_cleanup_scope {
1333 fcx.schedule_drop_mem(s, lldest, binding_info.ty);
1343 fn insert_lllocals<'a>(bcx: &'a Block<'a>,
1344 bindings_map: &BindingsMap,
1345 cleanup_scope: cleanup::ScopeId)
1348 * For each binding in `data.bindings_map`, adds an appropriate entry into
1349 * the `fcx.lllocals` map, scheduling cleanup in `cleanup_scope`.
1354 for (&ident, &binding_info) in bindings_map.iter() {
1355 let llval = match binding_info.trmode {
1356 // By value bindings: use the stack slot that we
1357 // copied/moved the value into
1358 TrByValue(lldest) => lldest,
1360 // By ref binding: use the ptr into the matched value
1361 TrByRef => binding_info.llmatch
1364 let datum = Datum(llval, binding_info.ty, Lvalue);
1365 fcx.schedule_drop_mem(cleanup_scope, llval, binding_info.ty);
1368 debug!("binding {:?} to {}",
1370 bcx.val_to_str(llval));
1371 let mut llmap = bcx.fcx.lllocals.borrow_mut();
1372 llmap.get().insert(binding_info.id, datum);
1375 if bcx.sess().opts.debuginfo {
1376 debuginfo::create_match_binding_metadata(bcx,
1386 fn compile_guard<'r,
1389 guard_expr: &ast::Expr,
1393 chk: &FailureHandler)
1395 debug!("compile_guard(bcx={}, guard_expr={}, m={}, vals={})",
1397 bcx.expr_to_str(guard_expr),
1399 vec_map_to_str(vals, |v| bcx.val_to_str(*v)));
1400 let _indenter = indenter();
1402 // Lest the guard itself should fail, introduce a temporary cleanup
1403 // scope for any non-ref bindings we create.
1404 let temp_scope = bcx.fcx.push_custom_cleanup_scope();
1407 bcx = store_non_ref_bindings(bcx, data.bindings_map,
1408 Some(cleanup::CustomScope(temp_scope)));
1409 bcx = insert_lllocals(bcx, data.bindings_map,
1410 cleanup::CustomScope(temp_scope));
1412 let val = unpack_datum!(bcx, expr::trans(bcx, guard_expr));
1413 let val = val.to_llbool(bcx);
1415 // Cancel cleanups now that the guard successfully executed. If
1416 // the guard was false, we will drop the values explicitly
1417 // below. Otherwise, we'll add lvalue cleanups at the end.
1418 bcx.fcx.pop_custom_cleanup_scope(temp_scope);
1420 return with_cond(bcx, Not(bcx, val), |bcx| {
1421 // Guard does not match: free the values we copied,
1422 // and remove all bindings from the lllocals table
1423 let bcx = drop_bindings(bcx, data);
1424 compile_submatch(bcx, m, vals, chk);
1428 fn drop_bindings<'a>(bcx: &'a Block<'a>, data: &ArmData)
1431 for (_, &binding_info) in data.bindings_map.iter() {
1432 match binding_info.trmode {
1433 TrByValue(llval) => {
1434 bcx = glue::drop_ty(bcx, llval, binding_info.ty);
1438 let mut lllocals = bcx.fcx.lllocals.borrow_mut();
1439 lllocals.get().remove(&binding_info.id);
1445 fn compile_submatch<'r,
1450 chk: &FailureHandler) {
1451 debug!("compile_submatch(bcx={}, m={}, vals={})",
1454 vec_map_to_str(vals, |v| bcx.val_to_str(*v)));
1455 let _indenter = indenter();
1458 For an empty match, a fall-through case must exist
1460 assert!((m.len() > 0u || chk.is_fallible()));
1461 let _icx = push_ctxt("match::compile_submatch");
1464 Br(bcx, chk.handle_fail());
1467 if m[0].pats.len() == 0u {
1468 let data = &m[0].data;
1469 for &(ref ident, ref value_ptr) in m[0].bound_ptrs.iter() {
1470 let llmatch = data.bindings_map.get(ident).llmatch;
1471 Store(bcx, *value_ptr, llmatch);
1473 match data.arm.guard {
1474 Some(guard_expr) => {
1475 bcx = compile_guard(bcx,
1478 m.slice(1, m.len()),
1484 Br(bcx, data.bodycx.llbb);
1488 let col = pick_col(m);
1489 let val = vals[col];
1491 if has_nested_bindings(m, col) {
1492 let expanded = expand_nested_bindings(bcx, m, col, val);
1493 compile_submatch_continue(bcx, expanded, vals, chk, col, val)
1495 compile_submatch_continue(bcx, m, vals, chk, col, val)
1499 fn compile_submatch_continue<'r,
1501 mut bcx: &'b Block<'b>,
1504 chk: &FailureHandler,
1508 let tcx = bcx.tcx();
1509 let dm = tcx.def_map;
1511 let vals_left = vec::append(vals.slice(0u, col).to_owned(),
1512 vals.slice(col + 1u, vals.len()));
1513 let ccx = bcx.fcx.ccx;
1515 for br in m.iter() {
1516 // Find a real id (we're adding placeholder wildcard patterns, but
1517 // each column is guaranteed to have at least one real pattern)
1519 pat_id = br.pats[col].id;
1523 // If we are not matching against an `@T`, we should not be
1524 // required to root any values.
1525 assert!(!pats_require_rooting(bcx, m, col));
1527 match collect_record_or_struct_fields(bcx, m, col) {
1528 Some(ref rec_fields) => {
1529 let pat_ty = node_id_type(bcx, pat_id);
1530 let pat_repr = adt::represent_type(bcx.ccx(), pat_ty);
1531 expr::with_field_tys(tcx, pat_ty, Some(pat_id), |discr, field_tys| {
1532 let rec_vals = rec_fields.map(|field_name| {
1533 let ix = ty::field_idx_strict(tcx, field_name.name, field_tys);
1534 adt::trans_field_ptr(bcx, pat_repr, val, discr, ix)
1538 enter_rec_or_struct(bcx, dm, m, col, *rec_fields, val),
1539 vec::append(rec_vals, vals_left),
1547 if any_tup_pat(m, col) {
1548 let tup_ty = node_id_type(bcx, pat_id);
1549 let tup_repr = adt::represent_type(bcx.ccx(), tup_ty);
1550 let n_tup_elts = match ty::get(tup_ty).sty {
1551 ty::ty_tup(ref elts) => elts.len(),
1552 _ => ccx.sess.bug("non-tuple type in tuple pattern")
1554 let tup_vals = vec::from_fn(n_tup_elts, |i| {
1555 adt::trans_field_ptr(bcx, tup_repr, val, 0, i)
1557 compile_submatch(bcx, enter_tup(bcx, dm, m, col, val, n_tup_elts),
1558 vec::append(tup_vals, vals_left), chk);
1562 if any_tuple_struct_pat(bcx, m, col) {
1563 let struct_ty = node_id_type(bcx, pat_id);
1564 let struct_element_count;
1565 match ty::get(struct_ty).sty {
1566 ty::ty_struct(struct_id, _) => {
1567 struct_element_count =
1568 ty::lookup_struct_fields(tcx, struct_id).len();
1571 ccx.sess.bug("non-struct type in tuple struct pattern");
1575 let struct_repr = adt::represent_type(bcx.ccx(), struct_ty);
1576 let llstructvals = vec::from_fn(struct_element_count, |i| {
1577 adt::trans_field_ptr(bcx, struct_repr, val, 0, i)
1579 compile_submatch(bcx,
1580 enter_tuple_struct(bcx, dm, m, col, val,
1581 struct_element_count),
1582 vec::append(llstructvals, vals_left),
1587 if any_uniq_pat(m, col) {
1588 let llbox = Load(bcx, val);
1589 compile_submatch(bcx, enter_uniq(bcx, dm, m, col, val),
1590 vec::append(~[llbox], vals_left), chk);
1594 if any_region_pat(m, col) {
1595 let loaded_val = Load(bcx, val);
1596 compile_submatch(bcx, enter_region(bcx, dm, m, col, val),
1597 vec::append(~[loaded_val], vals_left), chk);
1601 // Decide what kind of branch we need
1602 let opts = get_options(bcx, m, col);
1603 debug!("options={:?}", opts);
1604 let mut kind = no_branch;
1605 let mut test_val = val;
1606 debug!("test_val={}", bcx.val_to_str(test_val));
1607 if opts.len() > 0u {
1610 let (the_kind, val_opt) = adt::trans_switch(bcx, repr, val);
1612 for &tval in val_opt.iter() { test_val = tval; }
1615 let pty = node_id_type(bcx, pat_id);
1616 test_val = load_if_immediate(bcx, val, pty);
1617 kind = if ty::type_is_integral(pty) { switch }
1621 test_val = Load(bcx, val);
1625 let vt = tvec::vec_types(bcx, node_id_type(bcx, pat_id));
1626 let (_, len) = tvec::get_base_and_len(bcx, val, vt.vec_ty);
1628 kind = compare_vec_len;
1632 for o in opts.iter() {
1634 range(_, _) => { kind = compare; break }
1638 let else_cx = match kind {
1639 no_branch | single => bcx,
1640 _ => bcx.fcx.new_temp_block("match_else")
1642 let sw = if kind == switch {
1643 Switch(bcx, test_val, else_cx.llbb, opts.len())
1645 C_int(ccx, 0) // Placeholder for when not using a switch
1648 let defaults = enter_default(else_cx, dm, m, col, val, chk);
1649 let exhaustive = chk.is_infallible() && defaults.len() == 0u;
1650 let len = opts.len();
1652 // Compile subtrees for each option
1653 for (i, opt) in opts.iter().enumerate() {
1654 // In some cases in vector pattern matching, we need to override
1655 // the failure case so that instead of failing, it proceeds to
1656 // try more matching. branch_chk, then, is the proper failure case
1657 // for the current conditional branch.
1658 let mut branch_chk = None;
1659 let mut opt_cx = else_cx;
1660 if !exhaustive || i+1 < len {
1661 opt_cx = bcx.fcx.new_temp_block("match_case");
1663 single => Br(bcx, opt_cx.llbb),
1665 match trans_opt(bcx, opt) {
1666 single_result(r) => {
1668 llvm::LLVMAddCase(sw, r.val, opt_cx.llbb);
1674 "in compile_submatch, expected \
1675 trans_opt to return a single_result")
1680 let t = node_id_type(bcx, pat_id);
1681 let Result {bcx: after_cx, val: matches} = {
1682 match trans_opt(bcx, opt) {
1683 single_result(Result {bcx, val}) => {
1684 compare_values(bcx, test_val, val, t)
1686 lower_bound(Result {bcx, val}) => {
1687 compare_scalar_types(
1691 range_result(Result {val: vbegin, ..},
1692 Result {bcx, val: vend}) => {
1693 let Result {bcx, val: llge} =
1694 compare_scalar_types(
1696 vbegin, t, ast::BiGe);
1697 let Result {bcx, val: llle} =
1698 compare_scalar_types(
1699 bcx, test_val, vend,
1701 rslt(bcx, And(bcx, llge, llle))
1705 bcx = fcx.new_temp_block("compare_next");
1706 CondBr(after_cx, matches, opt_cx.llbb, bcx.llbb);
1708 compare_vec_len => {
1709 let Result {bcx: after_cx, val: matches} = {
1710 match trans_opt(bcx, opt) {
1712 Result {bcx, val}) => {
1713 let value = compare_scalar_values(
1715 signed_int, ast::BiEq);
1719 Result {bcx, val: val}) => {
1720 let value = compare_scalar_values(
1722 signed_int, ast::BiGe);
1726 Result {val: vbegin, ..},
1727 Result {bcx, val: vend}) => {
1729 compare_scalar_values(
1731 vbegin, signed_int, ast::BiGe);
1733 compare_scalar_values(
1734 bcx, test_val, vend,
1735 signed_int, ast::BiLe);
1736 rslt(bcx, And(bcx, llge, llle))
1740 bcx = fcx.new_temp_block("compare_vec_len_next");
1742 // If none of these subcases match, move on to the
1744 branch_chk = Some(JumpToBasicBlock(bcx.llbb));
1745 CondBr(after_cx, matches, opt_cx.llbb, bcx.llbb);
1749 } else if kind == compare || kind == compare_vec_len {
1750 Br(bcx, else_cx.llbb);
1754 let mut unpacked = ~[];
1756 var(disr_val, repr) => {
1757 let ExtractedBlock {vals: argvals, bcx: new_bcx} =
1758 extract_variant_args(opt_cx, repr, disr_val, val);
1759 size = argvals.len();
1763 vec_len(n, vt, _) => {
1764 let (n, slice) = match vt {
1765 vec_len_ge(i) => (n + 1u, Some(i)),
1766 vec_len_eq => (n, None)
1768 let args = extract_vec_elems(opt_cx, pat_id, n,
1769 slice, val, test_val);
1770 size = args.vals.len();
1771 unpacked = args.vals.clone();
1774 lit(_) | range(_, _) => ()
1776 let opt_ms = enter_opt(opt_cx, m, opt, col, size, val);
1777 let opt_vals = vec::append(unpacked, vals_left);
1780 None => compile_submatch(opt_cx, opt_ms, opt_vals, chk),
1781 Some(branch_chk) => {
1782 compile_submatch(opt_cx, opt_ms, opt_vals, &branch_chk)
1787 // Compile the fall-through case, if any
1789 if kind == compare || kind == compare_vec_len {
1790 Br(bcx, else_cx.llbb);
1793 compile_submatch(else_cx, defaults, vals_left, chk);
1798 pub fn trans_match<'a>(
1800 match_expr: &ast::Expr,
1801 discr_expr: &ast::Expr,
1805 let _icx = push_ctxt("match::trans_match");
1806 trans_match_inner(bcx, match_expr.id, discr_expr, arms, dest)
1809 fn create_bindings_map(bcx: &Block, pat: @ast::Pat) -> BindingsMap {
1810 // Create the bindings map, which is a mapping from each binding name
1811 // to an alloca() that will be the value for that local variable.
1812 // Note that we use the names because each binding will have many ids
1813 // from the various alternatives.
1814 let ccx = bcx.ccx();
1815 let tcx = bcx.tcx();
1816 let mut bindings_map = HashMap::new();
1817 pat_bindings(tcx.def_map, pat, |bm, p_id, span, path| {
1818 let ident = path_to_ident(path);
1819 let variable_ty = node_id_type(bcx, p_id);
1820 let llvariable_ty = type_of::type_of(ccx, variable_ty);
1825 ast::BindByValue(_) => {
1826 // in this case, the final type of the variable will be T,
1827 // but during matching we need to store a *T as explained
1829 llmatch = alloca(bcx, llvariable_ty.ptr_to(), "__llmatch");
1830 trmode = TrByValue(alloca(bcx, llvariable_ty,
1833 ast::BindByRef(_) => {
1834 llmatch = alloca(bcx, llvariable_ty, bcx.ident(ident));
1838 bindings_map.insert(ident, BindingInfo {
1846 return bindings_map;
1849 fn trans_match_inner<'a>(scope_cx: &'a Block<'a>,
1850 match_id: ast::NodeId,
1851 discr_expr: &ast::Expr,
1853 dest: Dest) -> &'a Block<'a> {
1854 let _icx = push_ctxt("match::trans_match_inner");
1855 let fcx = scope_cx.fcx;
1856 let mut bcx = scope_cx;
1857 let tcx = bcx.tcx();
1859 let discr_datum = unpack_datum!(bcx, expr::trans_to_lvalue(bcx, discr_expr,
1861 if bcx.unreachable.get() {
1865 let mut arm_datas = ~[];
1866 let mut matches = ~[];
1867 for arm in arms.iter() {
1868 let body = fcx.new_id_block("case_body", arm.body.id);
1869 let bindings_map = create_bindings_map(bcx, arm.pats[0]);
1870 let arm_data = ArmData {
1873 bindings_map: @bindings_map
1875 arm_datas.push(arm_data.clone());
1876 for p in arm.pats.iter() {
1877 matches.push(Match {
1879 data: arm_data.clone(),
1885 let t = node_id_type(bcx, discr_expr.id);
1887 if ty::type_is_empty(tcx, t) {
1888 // Special case for empty types
1889 let fail_cx = @Cell::new(None);
1890 let fail_handler = ~DynamicFailureHandler {
1892 sp: discr_expr.span,
1893 msg: InternedString::new("scrutinizing value that can't \
1897 DynamicFailureHandlerClass(fail_handler)
1902 let lldiscr = discr_datum.val;
1903 compile_submatch(bcx, matches, [lldiscr], &chk);
1905 let mut arm_cxs = ~[];
1906 for arm_data in arm_datas.iter() {
1907 let mut bcx = arm_data.bodycx;
1909 // If this arm has a guard, then the various by-value bindings have
1910 // already been copied into their homes. If not, we do it here. This
1911 // is just to reduce code space. See extensive comment at the start
1912 // of the file for more details.
1913 if arm_data.arm.guard.is_none() {
1914 bcx = store_non_ref_bindings(bcx, arm_data.bindings_map, None);
1917 // insert bindings into the lllocals map and add cleanups
1918 let cleanup_scope = fcx.push_custom_cleanup_scope();
1919 bcx = insert_lllocals(bcx, arm_data.bindings_map,
1920 cleanup::CustomScope(cleanup_scope));
1921 bcx = controlflow::trans_block(bcx, arm_data.arm.body, dest);
1922 bcx = fcx.pop_and_trans_custom_cleanup_scope(bcx, cleanup_scope);
1926 bcx = scope_cx.fcx.join_blocks(match_id, arm_cxs);
1930 enum IrrefutablePatternBindingMode {
1931 // Stores the association between node ID and LLVM value in `lllocals`.
1933 // Stores the association between node ID and LLVM value in `llargs`.
1937 pub fn store_local<'a>(bcx: &'a Block<'a>,
1941 * Generates code for a local variable declaration like
1942 * `let <pat>;` or `let <pat> = <opt_init_expr>`.
1944 let _icx = push_ctxt("match::store_local");
1946 let tcx = bcx.tcx();
1947 let pat = local.pat;
1948 let opt_init_expr = local.init;
1950 return match opt_init_expr {
1951 Some(init_expr) => {
1952 // Optimize the "let x = expr" case. This just writes
1953 // the result of evaluating `expr` directly into the alloca
1954 // for `x`. Often the general path results in similar or the
1955 // same code post-optimization, but not always. In particular,
1956 // in unsafe code, you can have expressions like
1958 // let x = intrinsics::uninit();
1960 // In such cases, the more general path is unsafe, because
1961 // it assumes it is matching against a valid value.
1962 match simple_identifier(pat) {
1964 let var_scope = cleanup::var_scope(tcx, local.id);
1965 return mk_binding_alloca(
1966 bcx, pat.id, path, BindLocal, var_scope, (),
1967 |(), bcx, v, _| expr::trans_into(bcx, init_expr,
1976 unpack_datum!(bcx, expr::trans_to_lvalue(bcx, init_expr, "let"));
1977 if ty::type_is_bot(expr_ty(bcx, init_expr)) {
1978 create_dummy_locals(bcx, pat)
1980 if bcx.sess().asm_comments() {
1981 add_comment(bcx, "creating zeroable ref llval");
1983 let var_scope = cleanup::var_scope(tcx, local.id);
1984 bind_irrefutable_pat(bcx, pat, init_datum.val, BindLocal, var_scope)
1988 create_dummy_locals(bcx, pat)
1992 fn create_dummy_locals<'a>(mut bcx: &'a Block<'a>,
1995 // create dummy memory for the variables if we have no
1996 // value to store into them immediately
1997 let tcx = bcx.tcx();
1998 pat_bindings(tcx.def_map, pat, |_, p_id, _, path| {
1999 let scope = cleanup::var_scope(tcx, p_id);
2000 bcx = mk_binding_alloca(
2001 bcx, p_id, path, BindLocal, scope, (),
2002 |(), bcx, llval, ty| { zero_mem(bcx, llval, ty); bcx });
2008 pub fn store_arg<'a>(mut bcx: &'a Block<'a>,
2011 arg_scope: cleanup::ScopeId)
2014 * Generates code for argument patterns like `fn foo(<pat>: T)`.
2015 * Creates entries in the `llargs` map for each of the bindings
2020 * - `pat` is the argument pattern
2021 * - `llval` is a pointer to the argument value (in other words,
2022 * if the argument type is `T`, then `llval` is a `T*`). In some
2023 * cases, this code may zero out the memory `llval` points at.
2026 let _icx = push_ctxt("match::store_arg");
2028 match simple_identifier(pat) {
2030 // Generate nicer LLVM for the common case of fn a pattern
2032 let arg_ty = node_id_type(bcx, pat.id);
2033 if type_of::arg_is_indirect(bcx.ccx(), arg_ty)
2034 && !bcx.ccx().sess.opts.debuginfo {
2035 // Don't copy an indirect argument to an alloca, the caller
2036 // already put it in a temporary alloca and gave it up, unless
2037 // we emit extra-debug-info, which requires local allocas :(.
2038 let arg_val = arg.add_clean(bcx.fcx, arg_scope);
2039 let mut llmap = bcx.fcx.llargs.borrow_mut();
2040 llmap.get().insert(pat.id, Datum(arg_val, arg_ty, Lvalue));
2044 bcx, pat.id, path, BindArgument, arg_scope, arg,
2045 |arg, bcx, llval, _| arg.store_to(bcx, llval))
2050 // General path. Copy out the values that are used in the
2052 let arg = unpack_datum!(
2053 bcx, arg.to_lvalue_datum_in_scope(bcx, "__arg", arg_scope));
2054 bind_irrefutable_pat(bcx, pat, arg.val,
2055 BindArgument, arg_scope)
2060 fn mk_binding_alloca<'a,A>(bcx: &'a Block<'a>,
2063 binding_mode: IrrefutablePatternBindingMode,
2064 cleanup_scope: cleanup::ScopeId,
2066 populate: |A, &'a Block<'a>, ValueRef, ty::t| -> &'a Block<'a>)
2068 let var_ty = node_id_type(bcx, p_id);
2069 let ident = ast_util::path_to_ident(path);
2071 // Allocate memory on stack for the binding.
2072 let llval = alloc_ty(bcx, var_ty, bcx.ident(ident));
2074 // Subtle: be sure that we *populate* the memory *before*
2075 // we schedule the cleanup.
2076 let bcx = populate(arg, bcx, llval, var_ty);
2077 bcx.fcx.schedule_drop_mem(cleanup_scope, llval, var_ty);
2079 // Now that memory is initialized and has cleanup scheduled,
2080 // create the datum and insert into the local variable map.
2081 let datum = Datum(llval, var_ty, Lvalue);
2082 let mut llmap = match binding_mode {
2083 BindLocal => bcx.fcx.lllocals.borrow_mut(),
2084 BindArgument => bcx.fcx.llargs.borrow_mut()
2086 llmap.get().insert(p_id, datum);
2090 fn bind_irrefutable_pat<'a>(
2094 binding_mode: IrrefutablePatternBindingMode,
2095 cleanup_scope: cleanup::ScopeId)
2098 * A simple version of the pattern matching code that only handles
2099 * irrefutable patterns. This is used in let/argument patterns,
2100 * not in match statements. Unifying this code with the code above
2101 * sounds nice, but in practice it produces very inefficient code,
2102 * since the match code is so much more general. In most cases,
2103 * LLVM is able to optimize the code, but it causes longer compile
2104 * times and makes the generated code nigh impossible to read.
2107 * - bcx: starting basic block context
2108 * - pat: the irrefutable pattern being matched.
2109 * - val: the value being matched -- must be an lvalue (by ref, with cleanup)
2110 * - binding_mode: is this for an argument or a local variable?
2113 debug!("bind_irrefutable_pat(bcx={}, pat={}, binding_mode={:?})",
2115 pat.repr(bcx.tcx()),
2118 if bcx.sess().asm_comments() {
2119 add_comment(bcx, format!("bind_irrefutable_pat(pat={})",
2120 pat.repr(bcx.tcx())));
2123 let _indenter = indenter();
2125 let _icx = push_ctxt("match::bind_irrefutable_pat");
2127 let tcx = bcx.tcx();
2128 let ccx = bcx.ccx();
2130 ast::PatIdent(pat_binding_mode, ref path, inner) => {
2131 if pat_is_binding(tcx.def_map, pat) {
2132 // Allocate the stack slot where the value of this
2133 // binding will live and place it into the appropriate
2135 bcx = mk_binding_alloca(
2136 bcx, pat.id, path, binding_mode, cleanup_scope, (),
2137 |(), bcx, llval, ty| {
2138 match pat_binding_mode {
2139 ast::BindByValue(_) => {
2140 // By value binding: move the value that `val`
2141 // points at into the binding's stack slot.
2142 let d = Datum(val, ty, Lvalue);
2143 d.store_to(bcx, llval)
2146 ast::BindByRef(_) => {
2147 // By ref binding: the value of the variable
2148 // is the pointer `val` itself.
2149 Store(bcx, val, llval);
2156 for &inner_pat in inner.iter() {
2157 bcx = bind_irrefutable_pat(bcx, inner_pat, val,
2158 binding_mode, cleanup_scope);
2161 ast::PatEnum(_, ref sub_pats) => {
2162 let def_map = bcx.tcx().def_map.borrow();
2163 match def_map.get().find(&pat.id) {
2164 Some(&ast::DefVariant(enum_id, var_id, _)) => {
2165 let repr = adt::represent_node(bcx, pat.id);
2166 let vinfo = ty::enum_variant_with_id(ccx.tcx,
2169 let args = extract_variant_args(bcx,
2173 for sub_pat in sub_pats.iter() {
2174 for (i, argval) in args.vals.iter().enumerate() {
2175 bcx = bind_irrefutable_pat(bcx, sub_pat[i],
2176 *argval, binding_mode,
2181 Some(&ast::DefFn(..)) |
2182 Some(&ast::DefStruct(..)) => {
2185 // This is a unit-like struct. Nothing to do here.
2187 Some(ref elems) => {
2188 // This is the tuple struct case.
2189 let repr = adt::represent_node(bcx, pat.id);
2190 for (i, elem) in elems.iter().enumerate() {
2191 let fldptr = adt::trans_field_ptr(bcx, repr,
2193 bcx = bind_irrefutable_pat(bcx, *elem,
2194 fldptr, binding_mode,
2200 Some(&ast::DefStatic(_, false)) => {
2203 // Nothing to do here.
2207 ast::PatStruct(_, ref fields, _) => {
2208 let tcx = bcx.tcx();
2209 let pat_ty = node_id_type(bcx, pat.id);
2210 let pat_repr = adt::represent_type(bcx.ccx(), pat_ty);
2211 expr::with_field_tys(tcx, pat_ty, Some(pat.id), |discr, field_tys| {
2212 for f in fields.iter() {
2213 let ix = ty::field_idx_strict(tcx, f.ident.name, field_tys);
2214 let fldptr = adt::trans_field_ptr(bcx, pat_repr, val,
2216 bcx = bind_irrefutable_pat(bcx, f.pat, fldptr,
2217 binding_mode, cleanup_scope);
2221 ast::PatTup(ref elems) => {
2222 let repr = adt::represent_node(bcx, pat.id);
2223 for (i, elem) in elems.iter().enumerate() {
2224 let fldptr = adt::trans_field_ptr(bcx, repr, val, 0, i);
2225 bcx = bind_irrefutable_pat(bcx, *elem, fldptr,
2226 binding_mode, cleanup_scope);
2229 ast::PatUniq(inner) => {
2230 let llbox = Load(bcx, val);
2231 bcx = bind_irrefutable_pat(bcx, inner, llbox, binding_mode, cleanup_scope);
2233 ast::PatRegion(inner) => {
2234 let loaded_val = Load(bcx, val);
2235 bcx = bind_irrefutable_pat(bcx, inner, loaded_val, binding_mode, cleanup_scope);
2237 ast::PatVec(..) => {
2238 bcx.tcx().sess.span_bug(
2240 format!("vector patterns are never irrefutable!"));
2242 ast::PatWild | ast::PatWildMulti | ast::PatLit(_) | ast::PatRange(_, _) => ()