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 an LLVM value which points at an alloca
68 * called `llmatch`. For by value bindings that are Copy, we also create
69 * an extra alloca that we copy the matched value to so that any changes
70 * we do to our copy is not reflected in the original and vice-versa.
71 * We don't do this if it's a move since the original value can't be used
72 * and thus allowing us to cheat in not creating an extra alloca.
74 * The `llmatch` binding always stores a pointer into the value being matched
75 * which points at the data for the binding. If the value being matched has
76 * type `T`, then, `llmatch` will point at an alloca of type `T*` (and hence
77 * `llmatch` has type `T**`). So, if you have a pattern like:
81 * match (a, b) { (ref c, d) => { ... } }
83 * For `c` and `d`, we would generate allocas of type `C*` and `D*`
84 * respectively. These are called the `llmatch`. As we match, when we come
85 * up against an identifier, we store the current pointer into the
86 * corresponding alloca.
88 * Once a pattern is completely matched, and assuming that there is no guard
89 * pattern, we will branch to a block that leads to the body itself. For any
90 * by-value bindings, this block will first load the ptr from `llmatch` (the
91 * one of type `D*`) and then load a second time to get the actual value (the
92 * one of type `D`). For by ref bindings, the value of the local variable is
93 * simply the first alloca.
95 * So, for the example above, we would generate a setup kind of like this:
101 * +--------------------------------------------+
102 * | llmatch_c = (addr of first half of tuple) |
103 * | llmatch_d = (addr of second half of tuple) |
104 * +--------------------------------------------+
106 * +--------------------------------------+
107 * | *llbinding_d = **llmatch_d |
108 * +--------------------------------------+
110 * If there is a guard, the situation is slightly different, because we must
111 * execute the guard code. Moreover, we need to do so once for each of the
112 * alternatives that lead to the arm, because if the guard fails, they may
113 * have different points from which to continue the search. Therefore, in that
114 * case, we generate code that looks more like:
120 * +-------------------------------------------+
121 * | llmatch_c = (addr of first half of tuple) |
122 * | llmatch_d = (addr of first half of tuple) |
123 * +-------------------------------------------+
125 * +-------------------------------------------------+
126 * | *llbinding_d = **llmatch_d |
127 * | check condition |
128 * | if false { goto next case } |
129 * | if true { goto body } |
130 * +-------------------------------------------------+
132 * The handling for the cleanups is a bit... sensitive. Basically, the body
133 * is the one that invokes `add_clean()` for each binding. During the guard
134 * evaluation, we add temporary cleanups and revoke them after the guard is
135 * evaluated (it could fail, after all). Note that guards and moves are
136 * just plain incompatible.
138 * Some relevant helper functions that manage bindings:
139 * - `create_bindings_map()`
140 * - `insert_lllocals()`
143 * ## Notes on vector pattern matching.
145 * Vector pattern matching is surprisingly tricky. The problem is that
146 * the structure of the vector isn't fully known, and slice matches
147 * can be done on subparts of it.
149 * The way that vector pattern matches are dealt with, then, is as
150 * follows. First, we make the actual condition associated with a
151 * vector pattern simply a vector length comparison. So the pattern
152 * [1, .. x] gets the condition "vec len >= 1", and the pattern
153 * [.. x] gets the condition "vec len >= 0". The problem here is that
154 * having the condition "vec len >= 1" hold clearly does not mean that
155 * only a pattern that has exactly that condition will match. This
156 * means that it may well be the case that a condition holds, but none
157 * of the patterns matching that condition match; to deal with this,
158 * when doing vector length matches, we have match failures proceed to
159 * the next condition to check.
161 * There are a couple more subtleties to deal with. While the "actual"
162 * condition associated with vector length tests is simply a test on
163 * the vector length, the actual vec_len Opt entry contains more
164 * information used to restrict which matches are associated with it.
165 * So that all matches in a submatch are matching against the same
166 * values from inside the vector, they are split up by how many
167 * elements they match at the front and at the back of the vector. In
168 * order to make sure that arms are properly checked in order, even
169 * with the overmatching conditions, each vec_len Opt entry is
170 * associated with a range of matches.
171 * Consider the following:
175 * [1, 2, 2, .. _] => 1,
176 * [1, 2, 3, .. _] => 2,
180 * The proper arm to match is arm 2, but arms 0 and 3 both have the
181 * condition "len >= 2". If arm 3 was lumped in with arm 0, then the
182 * wrong branch would be taken. Instead, vec_len Opts are associated
183 * with a contiguous range of matches that have the same "shape".
184 * This is sort of ugly and requires a bunch of special handling of
189 #![allow(non_camel_case_types)]
192 use driver::config::FullDebugInfo;
193 use lib::llvm::{llvm, ValueRef, BasicBlockRef};
194 use middle::const_eval;
196 use middle::check_match;
197 use middle::lang_items::StrEqFnLangItem;
198 use middle::pat_util::*;
199 use middle::resolve::DefMap;
200 use middle::trans::adt;
201 use middle::trans::base::*;
202 use middle::trans::build::*;
203 use middle::trans::callee;
204 use middle::trans::cleanup;
205 use middle::trans::cleanup::CleanupMethods;
206 use middle::trans::common::*;
207 use middle::trans::consts;
208 use middle::trans::controlflow;
209 use middle::trans::datum::*;
210 use middle::trans::expr::Dest;
211 use middle::trans::expr;
212 use middle::trans::tvec;
213 use middle::trans::type_of;
214 use middle::trans::debuginfo;
216 use util::common::indenter;
217 use util::ppaux::{Repr, vec_map_to_string};
220 use std::collections::HashMap;
225 use syntax::ast::Ident;
226 use syntax::codemap::Span;
227 use syntax::parse::token::InternedString;
229 // An option identifying a literal: either an expression or a DefId of a static expression.
231 ExprLit(Gc<ast::Expr>),
232 ConstLit(ast::DefId), // the def ID of the constant
235 #[deriving(PartialEq)]
238 vec_len_ge(/* length of prefix */uint)
241 // An option identifying a branch (either a literal, an enum variant or a
245 var(ty::Disr, Rc<adt::Repr>, ast::DefId),
246 range(Gc<ast::Expr>, Gc<ast::Expr>),
247 vec_len(/* length */ uint, VecLenOpt, /*range of matches*/(uint, uint))
250 fn lit_to_expr(tcx: &ty::ctxt, a: &Lit) -> Gc<ast::Expr> {
252 ExprLit(existing_a_expr) => existing_a_expr,
253 ConstLit(a_const) => const_eval::lookup_const_by_id(tcx, a_const).unwrap()
257 fn opt_eq(tcx: &ty::ctxt, a: &Opt, b: &Opt) -> bool {
259 (&lit(a), &lit(b)) => {
260 let a_expr = lit_to_expr(tcx, &a);
261 let b_expr = lit_to_expr(tcx, &b);
262 match const_eval::compare_lit_exprs(tcx, &*a_expr, &*b_expr) {
263 Some(val1) => val1 == 0,
264 None => fail!("compare_list_exprs: type mismatch"),
267 (&range(ref a1, ref a2), &range(ref b1, ref b2)) => {
268 let m1 = const_eval::compare_lit_exprs(tcx, &**a1, &**b1);
269 let m2 = const_eval::compare_lit_exprs(tcx, &**a2, &**b2);
271 (Some(val1), Some(val2)) => (val1 == 0 && val2 == 0),
272 _ => fail!("compare_list_exprs: type mismatch"),
275 (&var(a, _, _), &var(b, _, _)) => a == b,
276 (&vec_len(a1, a2, _), &vec_len(b1, b2, _)) =>
277 a1 == b1 && a2 == b2,
282 pub enum opt_result<'a> {
283 single_result(Result<'a>),
284 lower_bound(Result<'a>),
285 range_result(Result<'a>, Result<'a>),
288 fn trans_opt<'a>(bcx: &'a Block<'a>, o: &Opt) -> opt_result<'a> {
289 let _icx = push_ctxt("match::trans_opt");
293 lit(ExprLit(ref lit_expr)) => {
294 let lit_datum = unpack_datum!(bcx, expr::trans(bcx, &**lit_expr));
295 let lit_datum = lit_datum.assert_rvalue(bcx); // literals are rvalues
296 let lit_datum = unpack_datum!(bcx, lit_datum.to_appropriate_datum(bcx));
297 return single_result(Result::new(bcx, lit_datum.val));
299 lit(l @ ConstLit(ref def_id)) => {
300 let lit_ty = ty::node_id_to_type(bcx.tcx(), lit_to_expr(bcx.tcx(), &l).id);
301 let (llval, _) = consts::get_const_val(bcx.ccx(), *def_id);
302 let lit_datum = immediate_rvalue(llval, lit_ty);
303 let lit_datum = unpack_datum!(bcx, lit_datum.to_appropriate_datum(bcx));
304 return single_result(Result::new(bcx, lit_datum.val));
306 var(disr_val, ref repr, _) => {
307 return adt::trans_case(bcx, &**repr, disr_val);
309 range(ref l1, ref l2) => {
310 let (l1, _) = consts::const_expr(ccx, &**l1, true);
311 let (l2, _) = consts::const_expr(ccx, &**l2, true);
312 return range_result(Result::new(bcx, l1), Result::new(bcx, l2));
314 vec_len(n, vec_len_eq, _) => {
315 return single_result(Result::new(bcx, C_int(ccx, n as int)));
317 vec_len(n, vec_len_ge(_), _) => {
318 return lower_bound(Result::new(bcx, C_int(ccx, n as int)));
323 fn variant_opt(bcx: &Block, pat_id: ast::NodeId) -> Opt {
325 let def = ccx.tcx.def_map.borrow().get_copy(&pat_id);
327 def::DefVariant(enum_id, var_id, _) => {
328 let variant = ty::enum_variant_with_id(ccx.tcx(), enum_id, var_id);
329 var(variant.disr_val, adt::represent_node(bcx, pat_id), var_id)
332 ccx.sess().bug("non-variant or struct in variant_opt()");
338 pub enum TransBindingMode {
339 TrByCopy(/* llbinding */ ValueRef),
345 * Information about a pattern binding:
346 * - `llmatch` is a pointer to a stack slot. The stack slot contains a
347 * pointer into the value being matched. Hence, llmatch has type `T**`
348 * where `T` is the value being matched.
349 * - `trmode` is the trans binding mode
350 * - `id` is the node id of the binding
351 * - `ty` is the Rust type of the binding */
353 pub struct BindingInfo {
354 pub llmatch: ValueRef,
355 pub trmode: TransBindingMode,
361 type BindingsMap = HashMap<Ident, BindingInfo>;
363 struct ArmData<'a, 'b> {
364 bodycx: &'b Block<'b>,
366 bindings_map: BindingsMap
371 * If all `pats` are matched then arm `data` will be executed.
372 * As we proceed `bound_ptrs` are filled with pointers to values to be bound,
373 * these pointers are stored in llmatch variables just before executing `data` arm.
375 struct Match<'a, 'b> {
376 pats: Vec<Gc<ast::Pat>>,
377 data: &'a ArmData<'a, 'b>,
378 bound_ptrs: Vec<(Ident, ValueRef)>
381 impl<'a, 'b> Repr for Match<'a, 'b> {
382 fn repr(&self, tcx: &ty::ctxt) -> String {
383 if tcx.sess.verbose() {
384 // for many programs, this just take too long to serialize
387 format!("{} pats", self.pats.len())
392 fn has_nested_bindings(m: &[Match], col: uint) -> bool {
394 match br.pats.get(col).node {
395 ast::PatIdent(_, _, Some(_)) => return true,
402 fn expand_nested_bindings<'a, 'b>(
404 m: &'a [Match<'a, 'b>],
407 -> Vec<Match<'a, 'b>> {
408 debug!("expand_nested_bindings(bcx={}, m={}, col={}, val={})",
412 bcx.val_to_string(val));
413 let _indenter = indenter();
416 let mut bound_ptrs = br.bound_ptrs.clone();
417 let mut pat = *br.pats.get(col);
419 pat = match pat.node {
420 ast::PatIdent(_, ref path, Some(inner)) => {
421 bound_ptrs.push((path.node, val));
428 let mut pats = br.pats.clone();
429 *pats.get_mut(col) = pat;
433 bound_ptrs: bound_ptrs
438 type enter_pats<'a> = |&[Gc<ast::Pat>]|: 'a -> Option<Vec<Gc<ast::Pat>>>;
440 fn enter_match<'a, 'b>(
443 m: &'a [Match<'a, 'b>],
447 -> Vec<Match<'a, 'b>> {
448 debug!("enter_match(bcx={}, m={}, col={}, val={})",
452 bcx.val_to_string(val));
453 let _indenter = indenter();
455 m.iter().filter_map(|br| {
456 e(br.pats.as_slice()).map(|pats| {
457 let this = *br.pats.get(col);
458 let mut bound_ptrs = br.bound_ptrs.clone();
460 ast::PatIdent(_, ref path1, None) => {
461 if pat_is_binding(dm, &*this) {
462 bound_ptrs.push((path1.node, val));
471 bound_ptrs: bound_ptrs
477 fn enter_default<'a, 'b>(
480 m: &'a [Match<'a, 'b>],
483 -> Vec<Match<'a, 'b>> {
484 debug!("enter_default(bcx={}, m={}, col={}, val={})",
488 bcx.val_to_string(val));
489 let _indenter = indenter();
491 // Collect all of the matches that can match against anything.
492 enter_match(bcx, dm, m, col, val, |pats| {
493 if pat_is_binding_or_wild(dm, pats[col]) {
494 Some(Vec::from_slice(pats.slice_to(col)).append(pats.slice_from(col + 1)))
501 // <pcwalton> nmatsakis: what does enter_opt do?
502 // <pcwalton> in trans/match
503 // <pcwalton> trans/match.rs is like stumbling around in a dark cave
504 // <nmatsakis> pcwalton: the enter family of functions adjust the set of
505 // patterns as needed
506 // <nmatsakis> yeah, at some point I kind of achieved some level of
508 // <nmatsakis> anyhow, they adjust the patterns given that something of that
509 // kind has been found
510 // <nmatsakis> pcwalton: ok, right, so enter_XXX() adjusts the patterns, as I
512 // <nmatsakis> enter_match() kind of embodies the generic code
513 // <nmatsakis> it is provided with a function that tests each pattern to see
514 // if it might possibly apply and so forth
515 // <nmatsakis> so, if you have a pattern like {a: _, b: _, _} and one like _
516 // <nmatsakis> then _ would be expanded to (_, _)
517 // <nmatsakis> one spot for each of the sub-patterns
518 // <nmatsakis> enter_opt() is one of the more complex; it covers the fallible
520 // <nmatsakis> enter_rec_or_struct() or enter_tuple() are simpler, since they
521 // are infallible patterns
522 // <nmatsakis> so all patterns must either be records (resp. tuples) or
525 /// The above is now outdated in that enter_match() now takes a function that
526 /// takes the complete row of patterns rather than just the first one.
527 /// Also, most of the enter_() family functions have been unified with
528 /// the check_match specialization step.
529 fn enter_opt<'a, 'b>(
533 m: &'a [Match<'a, 'b>],
538 -> Vec<Match<'a, 'b>> {
539 debug!("enter_opt(bcx={}, m={}, opt={:?}, col={}, val={})",
544 bcx.val_to_string(val));
545 let _indenter = indenter();
547 let ctor = match opt {
548 &lit(x) => check_match::ConstantValue(const_eval::eval_const_expr(
549 bcx.tcx(), lit_to_expr(bcx.tcx(), &x))),
550 &range(ref lo, ref hi) => check_match::ConstantRange(
551 const_eval::eval_const_expr(bcx.tcx(), &**lo),
552 const_eval::eval_const_expr(bcx.tcx(), &**hi)
554 &vec_len(len, _, _) => check_match::Slice(len),
555 &var(_, _, def_id) => check_match::Variant(def_id)
560 let mcx = check_match::MatchCheckCtxt { tcx: bcx.tcx() };
561 enter_match(bcx, dm, m, col, val, |pats| {
562 let span = pats[col].span;
563 let specialized = match pats[col].node {
564 ast::PatVec(ref before, slice, ref after) => {
565 let (lo, hi) = match *opt {
566 vec_len(_, _, (lo, hi)) => (lo, hi),
567 _ => tcx.sess.span_bug(span,
568 "vec pattern but not vec opt")
571 let elems = match slice {
572 Some(slice) if i >= lo && i <= hi => {
573 let n = before.len() + after.len();
574 let this_opt = vec_len(n, vec_len_ge(before.len()),
576 if opt_eq(tcx, &this_opt, opt) {
577 let mut new_before = Vec::new();
578 for pat in before.iter() {
579 new_before.push(*pat);
581 new_before.push(slice);
582 for pat in after.iter() {
583 new_before.push(*pat);
590 None if i >= lo && i <= hi => {
591 let n = before.len();
592 if opt_eq(tcx, &vec_len(n, vec_len_eq, (lo,hi)), opt) {
593 let mut new_before = Vec::new();
594 for pat in before.iter() {
595 new_before.push(*pat);
604 elems.map(|head| head.append(pats.slice_to(col)).append(pats.slice_from(col + 1)))
607 check_match::specialize(&mcx, pats.as_slice(), &ctor, col, variant_size)
615 // Returns the options in one column of matches. An option is something that
616 // needs to be conditionally matched at runtime; for example, the discriminant
617 // on a set of enum variants or a literal.
618 fn get_options(bcx: &Block, m: &[Match], col: uint) -> Vec<Opt> {
620 fn add_to_set(tcx: &ty::ctxt, set: &mut Vec<Opt>, val: Opt) {
621 if set.iter().any(|l| opt_eq(tcx, l, &val)) {return;}
624 // Vector comparisons are special in that since the actual
625 // conditions over-match, we need to be careful about them. This
626 // means that in order to properly handle things in order, we need
627 // to not always merge conditions.
628 fn add_veclen_to_set(set: &mut Vec<Opt> , i: uint,
629 len: uint, vlo: VecLenOpt) {
631 // If the last condition in the list matches the one we want
632 // to add, then extend its range. Otherwise, make a new
633 // vec_len with a range just covering the new entry.
634 Some(&vec_len(len2, vlo2, (start, end)))
635 if len == len2 && vlo == vlo2 => {
636 let length = set.len();
637 *set.get_mut(length - 1) =
638 vec_len(len, vlo, (start, end+1))
640 _ => set.push(vec_len(len, vlo, (i, i)))
644 let mut found = Vec::new();
645 for (i, br) in m.iter().enumerate() {
646 let cur = *br.pats.get(col);
649 add_to_set(ccx.tcx(), &mut found, lit(ExprLit(l)));
651 ast::PatIdent(..) => {
652 // This is either an enum variant or a variable binding.
653 let opt_def = ccx.tcx.def_map.borrow().find_copy(&cur.id);
655 Some(def::DefVariant(..)) => {
656 add_to_set(ccx.tcx(), &mut found,
657 variant_opt(bcx, cur.id));
659 Some(def::DefStatic(const_did, false)) => {
660 add_to_set(ccx.tcx(), &mut found,
661 lit(ConstLit(const_did)));
666 ast::PatEnum(..) | ast::PatStruct(..) => {
667 // This could be one of: a tuple-like enum variant, a
668 // struct-like enum variant, or a struct.
669 let opt_def = ccx.tcx.def_map.borrow().find_copy(&cur.id);
671 Some(def::DefFn(..)) |
672 Some(def::DefVariant(..)) => {
673 add_to_set(ccx.tcx(), &mut found,
674 variant_opt(bcx, cur.id));
676 Some(def::DefStatic(const_did, false)) => {
677 add_to_set(ccx.tcx(), &mut found,
678 lit(ConstLit(const_did)));
683 ast::PatRange(l1, l2) => {
684 add_to_set(ccx.tcx(), &mut found, range(l1, l2));
686 ast::PatVec(ref before, slice, ref after) => {
687 let (len, vec_opt) = match slice {
688 None => (before.len(), vec_len_eq),
689 Some(_) => (before.len() + after.len(),
690 vec_len_ge(before.len()))
692 add_veclen_to_set(&mut found, i, len, vec_opt);
700 struct ExtractedBlock<'a> {
701 vals: Vec<ValueRef> ,
705 fn extract_variant_args<'a>(
710 -> ExtractedBlock<'a> {
711 let _icx = push_ctxt("match::extract_variant_args");
712 let args = Vec::from_fn(adt::num_args(repr, disr_val), |i| {
713 adt::trans_field_ptr(bcx, repr, val, disr_val, i)
716 ExtractedBlock { vals: args, bcx: bcx }
719 fn match_datum(bcx: &Block,
724 * Helper for converting from the ValueRef that we pass around in
725 * the match code, which is always an lvalue, into a Datum. Eventually
726 * we should just pass around a Datum and be done with it.
729 let ty = node_id_type(bcx, pat_id);
730 Datum::new(val, ty, Lvalue)
734 fn extract_vec_elems<'a>(
740 -> ExtractedBlock<'a> {
741 let _icx = push_ctxt("match::extract_vec_elems");
742 let vec_datum = match_datum(bcx, val, pat_id);
743 let (base, len) = vec_datum.get_vec_base_and_len(bcx);
744 let vec_ty = node_id_type(bcx, pat_id);
745 let vt = tvec::vec_types(bcx, ty::sequence_element_type(bcx.tcx(), vec_ty));
747 let mut elems = Vec::from_fn(elem_count, |i| {
749 None => GEPi(bcx, base, [i]),
750 Some(n) if i < n => GEPi(bcx, base, [i]),
751 Some(n) if i > n => {
752 InBoundsGEP(bcx, base, [
754 C_int(bcx.ccx(), (elem_count - i) as int))])
756 _ => unsafe { llvm::LLVMGetUndef(vt.llunit_ty.to_ref()) }
760 let n = slice.unwrap();
761 let slice_byte_offset = Mul(bcx, vt.llunit_size, C_uint(bcx.ccx(), n));
762 let slice_begin = tvec::pointer_add_byte(bcx, base, slice_byte_offset);
763 let slice_len_offset = C_uint(bcx.ccx(), elem_count - 1u);
764 let slice_len = Sub(bcx, len, slice_len_offset);
765 let slice_ty = ty::mk_slice(bcx.tcx(),
767 ty::mt {ty: vt.unit_ty, mutbl: ast::MutImmutable});
768 let scratch = rvalue_scratch_datum(bcx, slice_ty, "");
769 Store(bcx, slice_begin,
770 GEPi(bcx, scratch.val, [0u, abi::slice_elt_base]));
771 Store(bcx, slice_len, GEPi(bcx, scratch.val, [0u, abi::slice_elt_len]));
772 *elems.get_mut(n) = scratch.val;
775 ExtractedBlock { vals: elems, bcx: bcx }
778 // Macro for deciding whether any of the remaining matches fit a given kind of
779 // pattern. Note that, because the macro is well-typed, either ALL of the
780 // matches should fit that sort of pattern or NONE (however, some of the
781 // matches may be wildcards like _ or identifiers).
782 macro_rules! any_pat (
783 ($m:expr, $col:expr, $pattern:pat) => (
784 ($m).iter().any(|br| {
785 match br.pats.get($col).node {
793 fn any_uniq_pat(m: &[Match], col: uint) -> bool {
794 any_pat!(m, col, ast::PatBox(_))
797 fn any_region_pat(m: &[Match], col: uint) -> bool {
798 any_pat!(m, col, ast::PatRegion(_))
801 fn any_irrefutable_adt_pat(bcx: &Block, m: &[Match], col: uint) -> bool {
803 let pat = *br.pats.get(col);
805 ast::PatTup(_) => true,
806 ast::PatStruct(..) => {
807 match bcx.tcx().def_map.borrow().find(&pat.id) {
808 Some(&def::DefVariant(..)) => false,
812 ast::PatEnum(..) | ast::PatIdent(_, _, None) => {
813 match bcx.tcx().def_map.borrow().find(&pat.id) {
814 Some(&def::DefFn(..)) |
815 Some(&def::DefStruct(..)) => true,
824 struct DynamicFailureHandler<'a> {
828 finished: Cell<Option<BasicBlockRef>>,
831 impl<'a> DynamicFailureHandler<'a> {
832 fn handle_fail(&self) -> BasicBlockRef {
833 match self.finished.get() {
834 Some(bb) => return bb,
838 let fcx = self.bcx.fcx;
839 let fail_cx = fcx.new_block(false, "case_fallthrough", None);
840 controlflow::trans_fail(fail_cx, self.sp, self.msg.clone());
841 self.finished.set(Some(fail_cx.llbb));
846 /// What to do when the pattern match fails.
847 enum FailureHandler<'a> {
849 JumpToBasicBlock(BasicBlockRef),
850 DynamicFailureHandlerClass(Box<DynamicFailureHandler<'a>>),
853 impl<'a> FailureHandler<'a> {
854 fn is_infallible(&self) -> bool {
861 fn is_fallible(&self) -> bool {
862 !self.is_infallible()
865 fn handle_fail(&self) -> BasicBlockRef {
868 fail!("attempted to fail in infallible failure handler!")
870 JumpToBasicBlock(basic_block) => basic_block,
871 DynamicFailureHandlerClass(ref dynamic_failure_handler) => {
872 dynamic_failure_handler.handle_fail()
878 fn pick_col(m: &[Match]) -> uint {
879 fn score(p: &ast::Pat) -> uint {
881 ast::PatLit(_) | ast::PatEnum(_, _) | ast::PatRange(_, _) => 1u,
882 ast::PatIdent(_, _, Some(ref p)) => score(&**p),
886 let mut scores = Vec::from_elem(m[0].pats.len(), 0u);
888 for (i, ref p) in br.pats.iter().enumerate() {
889 *scores.get_mut(i) += score(&***p);
892 let mut max_score = 0u;
893 let mut best_col = 0u;
894 for (i, score) in scores.iter().enumerate() {
897 // Irrefutable columns always go first, they'd only be duplicated in
899 if score == 0u { return i; }
900 // If no irrefutable ones are found, we pick the one with the biggest
902 if score > max_score { max_score = score; best_col = i; }
907 #[deriving(PartialEq)]
908 pub enum branch_kind { no_branch, single, switch, compare, compare_vec_len }
910 // Compiles a comparison between two things.
911 fn compare_values<'a>(
917 fn compare_str<'a>(cx: &'a Block<'a>,
922 let did = langcall(cx,
924 format!("comparison of `{}`",
925 cx.ty_to_string(rhs_t)).as_slice(),
927 callee::trans_lang_call(cx, did, [lhs, rhs], None)
930 let _icx = push_ctxt("compare_values");
931 if ty::type_is_scalar(rhs_t) {
932 let rs = compare_scalar_types(cx, lhs, rhs, rhs_t, ast::BiEq);
933 return Result::new(rs.bcx, rs.val);
936 match ty::get(rhs_t).sty {
937 ty::ty_rptr(_, mt) => match ty::get(mt.ty).sty {
938 ty::ty_str => compare_str(cx, lhs, rhs, rhs_t),
939 ty::ty_vec(mt, _) => match ty::get(mt.ty).sty {
940 ty::ty_uint(ast::TyU8) => {
941 // NOTE: cast &[u8] to &str and abuse the str_eq lang item,
942 // which calls memcmp().
943 let t = ty::mk_str_slice(cx.tcx(), ty::ReStatic, ast::MutImmutable);
944 let lhs = BitCast(cx, lhs, type_of::type_of(cx.ccx(), t).ptr_to());
945 let rhs = BitCast(cx, rhs, type_of::type_of(cx.ccx(), t).ptr_to());
946 compare_str(cx, lhs, rhs, rhs_t)
948 _ => cx.sess().bug("only byte strings supported in compare_values"),
950 _ => cx.sess().bug("only string and byte strings supported in compare_values"),
952 _ => cx.sess().bug("only scalars, byte strings, and strings supported in compare_values"),
956 fn insert_lllocals<'a>(mut bcx: &'a Block<'a>, bindings_map: &BindingsMap,
957 cs: Option<cleanup::ScopeId>)
960 * For each binding in `data.bindings_map`, adds an appropriate entry into
961 * the `fcx.lllocals` map
964 for (&ident, &binding_info) in bindings_map.iter() {
965 let llval = match binding_info.trmode {
966 // By value mut binding for a copy type: load from the ptr
967 // into the matched value and copy to our alloca
968 TrByCopy(llbinding) => {
969 let llval = Load(bcx, binding_info.llmatch);
970 let datum = Datum::new(llval, binding_info.ty, Lvalue);
971 bcx = datum.store_to(bcx, llbinding);
976 // By value move bindings: load from the ptr into the matched value
977 TrByMove => Load(bcx, binding_info.llmatch),
979 // By ref binding: use the ptr into the matched value
980 TrByRef => binding_info.llmatch
983 let datum = Datum::new(llval, binding_info.ty, Lvalue);
985 Some(cs) => bcx.fcx.schedule_drop_and_zero_mem(cs, llval, binding_info.ty),
989 debug!("binding {:?} to {}",
991 bcx.val_to_string(llval));
992 bcx.fcx.lllocals.borrow_mut().insert(binding_info.id, datum);
994 if bcx.sess().opts.debuginfo == FullDebugInfo {
995 debuginfo::create_match_binding_metadata(bcx,
1003 fn compile_guard<'a, 'b>(
1005 guard_expr: &ast::Expr,
1007 m: &'a [Match<'a, 'b>],
1009 chk: &FailureHandler,
1010 has_genuine_default: bool)
1012 debug!("compile_guard(bcx={}, guard_expr={}, m={}, vals={})",
1014 bcx.expr_to_string(guard_expr),
1016 vec_map_to_string(vals, |v| bcx.val_to_string(*v)));
1017 let _indenter = indenter();
1019 let mut bcx = insert_lllocals(bcx, &data.bindings_map, None);
1021 let val = unpack_datum!(bcx, expr::trans(bcx, guard_expr));
1022 let val = val.to_llbool(bcx);
1024 return with_cond(bcx, Not(bcx, val), |bcx| {
1025 // Guard does not match: remove all bindings from the lllocals table
1026 for (_, &binding_info) in data.bindings_map.iter() {
1027 bcx.fcx.lllocals.borrow_mut().remove(&binding_info.id);
1030 // If the default arm is the only one left, move on to the next
1031 // condition explicitly rather than (possibly) falling back to
1033 &JumpToBasicBlock(_) if m.len() == 1 && has_genuine_default => {
1034 Br(bcx, chk.handle_fail());
1037 compile_submatch(bcx, m, vals, chk, has_genuine_default);
1044 fn compile_submatch<'a, 'b>(
1046 m: &'a [Match<'a, 'b>],
1048 chk: &FailureHandler,
1049 has_genuine_default: bool) {
1050 debug!("compile_submatch(bcx={}, m={}, vals={})",
1053 vec_map_to_string(vals, |v| bcx.val_to_string(*v)));
1054 let _indenter = indenter();
1055 let _icx = push_ctxt("match::compile_submatch");
1058 if chk.is_fallible() {
1059 Br(bcx, chk.handle_fail());
1063 if m[0].pats.len() == 0u {
1064 let data = &m[0].data;
1065 for &(ref ident, ref value_ptr) in m[0].bound_ptrs.iter() {
1066 let llmatch = data.bindings_map.get(ident).llmatch;
1067 Store(bcx, *value_ptr, llmatch);
1069 match data.arm.guard {
1070 Some(ref guard_expr) => {
1071 bcx = compile_guard(bcx,
1074 m.slice(1, m.len()),
1077 has_genuine_default);
1081 Br(bcx, data.bodycx.llbb);
1085 let col = pick_col(m);
1086 let val = vals[col];
1088 if has_nested_bindings(m, col) {
1089 let expanded = expand_nested_bindings(bcx, m, col, val);
1090 compile_submatch_continue(bcx,
1091 expanded.as_slice(),
1096 has_genuine_default)
1098 compile_submatch_continue(bcx, m, vals, chk, col, val, has_genuine_default)
1102 fn compile_submatch_continue<'a, 'b>(
1103 mut bcx: &'b Block<'b>,
1104 m: &'a [Match<'a, 'b>],
1106 chk: &FailureHandler,
1109 has_genuine_default: bool) {
1111 let tcx = bcx.tcx();
1112 let dm = &tcx.def_map;
1114 let vals_left = Vec::from_slice(vals.slice(0u, col)).append(vals.slice(col + 1u, vals.len()));
1115 let ccx = bcx.fcx.ccx;
1117 // Find a real id (we're adding placeholder wildcard patterns, but
1118 // each column is guaranteed to have at least one real pattern)
1119 let pat_id = m.iter().map(|br| br.pats.get(col).id).find(|&id| id != 0).unwrap_or(0);
1121 let left_ty = if pat_id == 0 {
1124 node_id_type(bcx, pat_id)
1127 let mcx = check_match::MatchCheckCtxt { tcx: bcx.tcx() };
1128 let adt_vals = if any_irrefutable_adt_pat(bcx, m, col) {
1129 let repr = adt::represent_type(bcx.ccx(), left_ty);
1130 let arg_count = adt::num_args(&*repr, 0);
1131 let field_vals: Vec<ValueRef> = std::iter::range(0, arg_count).map(|ix|
1132 adt::trans_field_ptr(bcx, &*repr, val, 0, ix)
1135 } else if any_uniq_pat(m, col) || any_region_pat(m, col) {
1136 Some(vec!(Load(bcx, val)))
1142 Some(field_vals) => {
1143 let pats = enter_match(bcx, dm, m, col, val, |pats|
1144 check_match::specialize(&mcx, pats, &check_match::Single, col, field_vals.len())
1146 let vals = field_vals.append(vals_left.as_slice());
1147 compile_submatch(bcx, pats.as_slice(), vals.as_slice(), chk, has_genuine_default);
1153 // Decide what kind of branch we need
1154 let opts = get_options(bcx, m, col);
1155 debug!("options={:?}", opts);
1156 let mut kind = no_branch;
1157 let mut test_val = val;
1158 debug!("test_val={}", bcx.val_to_string(test_val));
1159 if opts.len() > 0u {
1160 match *opts.get(0) {
1161 var(_, ref repr, _) => {
1162 let (the_kind, val_opt) = adt::trans_switch(bcx, &**repr, val);
1164 for &tval in val_opt.iter() { test_val = tval; }
1167 test_val = load_if_immediate(bcx, val, left_ty);
1168 kind = if ty::type_is_integral(left_ty) { switch }
1172 test_val = Load(bcx, val);
1176 let (_, len) = tvec::get_base_and_len(bcx, val, left_ty);
1178 kind = compare_vec_len;
1182 for o in opts.iter() {
1184 range(_, _) => { kind = compare; break }
1188 let else_cx = match kind {
1189 no_branch | single => bcx,
1190 _ => bcx.fcx.new_temp_block("match_else")
1192 let sw = if kind == switch {
1193 Switch(bcx, test_val, else_cx.llbb, opts.len())
1195 C_int(ccx, 0) // Placeholder for when not using a switch
1198 let defaults = enter_default(else_cx, dm, m, col, val);
1199 let exhaustive = chk.is_infallible() && defaults.len() == 0u;
1200 let len = opts.len();
1202 // Compile subtrees for each option
1203 for (i, opt) in opts.iter().enumerate() {
1204 // In some cases of range and vector pattern matching, we need to
1205 // override the failure case so that instead of failing, it proceeds
1206 // to try more matching. branch_chk, then, is the proper failure case
1207 // for the current conditional branch.
1208 let mut branch_chk = None;
1209 let mut opt_cx = else_cx;
1210 if !exhaustive || i+1 < len {
1211 opt_cx = bcx.fcx.new_temp_block("match_case");
1213 single => Br(bcx, opt_cx.llbb),
1215 match trans_opt(bcx, opt) {
1216 single_result(r) => {
1218 llvm::LLVMAddCase(sw, r.val, opt_cx.llbb);
1224 "in compile_submatch, expected \
1225 trans_opt to return a single_result")
1229 compare | compare_vec_len => {
1230 let t = if kind == compare {
1233 ty::mk_uint() // vector length
1235 let Result {bcx: after_cx, val: matches} = {
1236 match trans_opt(bcx, opt) {
1237 single_result(Result {bcx, val}) => {
1238 compare_values(bcx, test_val, val, t)
1240 lower_bound(Result {bcx, val}) => {
1241 compare_scalar_types(bcx, test_val, val, t, ast::BiGe)
1243 range_result(Result {val: vbegin, ..},
1244 Result {bcx, val: vend}) => {
1245 let Result {bcx, val: llge} =
1246 compare_scalar_types(
1248 vbegin, t, ast::BiGe);
1249 let Result {bcx, val: llle} =
1250 compare_scalar_types(
1251 bcx, test_val, vend,
1253 Result::new(bcx, And(bcx, llge, llle))
1257 bcx = fcx.new_temp_block("compare_next");
1259 // If none of the sub-cases match, and the current condition
1260 // is guarded or has multiple patterns, move on to the next
1261 // condition, if there is any, rather than falling back to
1263 let guarded = m[i].data.arm.guard.is_some();
1264 let multi_pats = m[i].pats.len() > 1;
1265 if i + 1 < len && (guarded || multi_pats || kind == compare_vec_len) {
1266 branch_chk = Some(JumpToBasicBlock(bcx.llbb));
1268 CondBr(after_cx, matches, opt_cx.llbb, bcx.llbb);
1272 } else if kind == compare || kind == compare_vec_len {
1273 Br(bcx, else_cx.llbb);
1277 let mut unpacked = Vec::new();
1279 var(disr_val, ref repr, _) => {
1280 let ExtractedBlock {vals: argvals, bcx: new_bcx} =
1281 extract_variant_args(opt_cx, &**repr, disr_val, val);
1282 size = argvals.len();
1286 vec_len(n, vt, _) => {
1287 let (n, slice) = match vt {
1288 vec_len_ge(i) => (n + 1u, Some(i)),
1289 vec_len_eq => (n, None)
1291 let args = extract_vec_elems(opt_cx, pat_id, n,
1293 size = args.vals.len();
1294 unpacked = args.vals.clone();
1297 lit(_) | range(_, _) => ()
1299 let opt_ms = enter_opt(opt_cx, pat_id, dm, m, opt, col, size, val);
1300 let opt_vals = unpacked.append(vals_left.as_slice());
1304 compile_submatch(opt_cx,
1306 opt_vals.as_slice(),
1308 has_genuine_default)
1310 Some(branch_chk) => {
1311 compile_submatch(opt_cx,
1313 opt_vals.as_slice(),
1315 has_genuine_default)
1320 // Compile the fall-through case, if any
1321 if !exhaustive && kind != single {
1322 if kind == compare || kind == compare_vec_len {
1323 Br(bcx, else_cx.llbb);
1326 // If there is only one default arm left, move on to the next
1327 // condition explicitly rather than (eventually) falling back to
1328 // the last default arm.
1329 &JumpToBasicBlock(_) if defaults.len() == 1 && has_genuine_default => {
1330 Br(else_cx, chk.handle_fail());
1333 compile_submatch(else_cx,
1334 defaults.as_slice(),
1335 vals_left.as_slice(),
1337 has_genuine_default);
1343 pub fn trans_match<'a>(
1345 match_expr: &ast::Expr,
1346 discr_expr: &ast::Expr,
1350 let _icx = push_ctxt("match::trans_match");
1351 trans_match_inner(bcx, match_expr.id, discr_expr, arms, dest)
1354 fn create_bindings_map(bcx: &Block, pat: Gc<ast::Pat>) -> BindingsMap {
1355 // Create the bindings map, which is a mapping from each binding name
1356 // to an alloca() that will be the value for that local variable.
1357 // Note that we use the names because each binding will have many ids
1358 // from the various alternatives.
1359 let ccx = bcx.ccx();
1360 let tcx = bcx.tcx();
1361 let mut bindings_map = HashMap::new();
1362 pat_bindings(&tcx.def_map, &*pat, |bm, p_id, span, path1| {
1363 let ident = path1.node;
1364 let variable_ty = node_id_type(bcx, p_id);
1365 let llvariable_ty = type_of::type_of(ccx, variable_ty);
1366 let tcx = bcx.tcx();
1372 if !ty::type_moves_by_default(tcx, variable_ty) => {
1373 llmatch = alloca(bcx,
1374 llvariable_ty.ptr_to(),
1376 trmode = TrByCopy(alloca(bcx,
1378 bcx.ident(ident).as_slice()));
1380 ast::BindByValue(_) => {
1381 // in this case, the final type of the variable will be T,
1382 // but during matching we need to store a *T as explained
1384 llmatch = alloca(bcx,
1385 llvariable_ty.ptr_to(),
1386 bcx.ident(ident).as_slice());
1389 ast::BindByRef(_) => {
1390 llmatch = alloca(bcx,
1392 bcx.ident(ident).as_slice());
1396 bindings_map.insert(ident, BindingInfo {
1404 return bindings_map;
1407 fn trans_match_inner<'a>(scope_cx: &'a Block<'a>,
1408 match_id: ast::NodeId,
1409 discr_expr: &ast::Expr,
1411 dest: Dest) -> &'a Block<'a> {
1412 let _icx = push_ctxt("match::trans_match_inner");
1413 let fcx = scope_cx.fcx;
1414 let mut bcx = scope_cx;
1415 let tcx = bcx.tcx();
1417 let discr_datum = unpack_datum!(bcx, expr::trans_to_lvalue(bcx, discr_expr,
1419 if bcx.unreachable.get() {
1423 let t = node_id_type(bcx, discr_expr.id);
1425 if ty::type_is_empty(tcx, t) {
1426 // Special case for empty types
1427 let fail_cx = Cell::new(None);
1428 let fail_handler = box DynamicFailureHandler {
1430 sp: discr_expr.span,
1431 msg: InternedString::new("scrutinizing value that can't \
1435 DynamicFailureHandlerClass(fail_handler)
1441 let arm_datas: Vec<ArmData> = arms.iter().map(|arm| ArmData {
1442 bodycx: fcx.new_id_block("case_body", arm.body.id),
1444 bindings_map: create_bindings_map(bcx, *arm.pats.get(0))
1447 let mut matches = Vec::new();
1448 for arm_data in arm_datas.iter() {
1449 matches.extend(arm_data.arm.pats.iter().map(|p| Match {
1452 bound_ptrs: Vec::new(),
1456 // `compile_submatch` works one column of arm patterns a time and
1457 // then peels that column off. So as we progress, it may become
1458 // impossible to tell whether we have a genuine default arm, i.e.
1459 // `_ => foo` or not. Sometimes it is important to know that in order
1460 // to decide whether moving on to the next condition or falling back
1461 // to the default arm.
1462 let has_default = arms.last().map_or(false, |arm| {
1464 && arm.pats.last().unwrap().node == ast::PatWild
1467 compile_submatch(bcx, matches.as_slice(), [discr_datum.val], &chk, has_default);
1469 let mut arm_cxs = Vec::new();
1470 for arm_data in arm_datas.iter() {
1471 let mut bcx = arm_data.bodycx;
1473 // insert bindings into the lllocals map and add cleanups
1474 let cs = fcx.push_custom_cleanup_scope();
1475 bcx = insert_lllocals(bcx, &arm_data.bindings_map, Some(cleanup::CustomScope(cs)));
1476 bcx = expr::trans_into(bcx, &*arm_data.arm.body, dest);
1477 bcx = fcx.pop_and_trans_custom_cleanup_scope(bcx, cs);
1481 bcx = scope_cx.fcx.join_blocks(match_id, arm_cxs.as_slice());
1485 enum IrrefutablePatternBindingMode {
1486 // Stores the association between node ID and LLVM value in `lllocals`.
1488 // Stores the association between node ID and LLVM value in `llargs`.
1492 pub fn store_local<'a>(bcx: &'a Block<'a>,
1496 * Generates code for a local variable declaration like
1497 * `let <pat>;` or `let <pat> = <opt_init_expr>`.
1499 let _icx = push_ctxt("match::store_local");
1501 let tcx = bcx.tcx();
1502 let pat = local.pat;
1503 let opt_init_expr = local.init;
1505 return match opt_init_expr {
1506 Some(init_expr) => {
1507 // Optimize the "let x = expr" case. This just writes
1508 // the result of evaluating `expr` directly into the alloca
1509 // for `x`. Often the general path results in similar or the
1510 // same code post-optimization, but not always. In particular,
1511 // in unsafe code, you can have expressions like
1513 // let x = intrinsics::uninit();
1515 // In such cases, the more general path is unsafe, because
1516 // it assumes it is matching against a valid value.
1517 match simple_identifier(&*pat) {
1519 let var_scope = cleanup::var_scope(tcx, local.id);
1520 return mk_binding_alloca(
1521 bcx, pat.id, ident, BindLocal, var_scope, (),
1522 |(), bcx, v, _| expr::trans_into(bcx, &*init_expr,
1531 unpack_datum!(bcx, expr::trans_to_lvalue(bcx, &*init_expr, "let"));
1532 if ty::type_is_bot(expr_ty(bcx, &*init_expr)) {
1533 create_dummy_locals(bcx, pat)
1535 if bcx.sess().asm_comments() {
1536 add_comment(bcx, "creating zeroable ref llval");
1538 let var_scope = cleanup::var_scope(tcx, local.id);
1539 bind_irrefutable_pat(bcx, pat, init_datum.val, BindLocal, var_scope)
1543 create_dummy_locals(bcx, pat)
1547 fn create_dummy_locals<'a>(mut bcx: &'a Block<'a>,
1550 // create dummy memory for the variables if we have no
1551 // value to store into them immediately
1552 let tcx = bcx.tcx();
1553 pat_bindings(&tcx.def_map, &*pat, |_, p_id, _, path1| {
1554 let scope = cleanup::var_scope(tcx, p_id);
1555 bcx = mk_binding_alloca(
1556 bcx, p_id, &path1.node, BindLocal, scope, (),
1557 |(), bcx, llval, ty| { zero_mem(bcx, llval, ty); bcx });
1563 pub fn store_arg<'a>(mut bcx: &'a Block<'a>,
1566 arg_scope: cleanup::ScopeId)
1569 * Generates code for argument patterns like `fn foo(<pat>: T)`.
1570 * Creates entries in the `llargs` map for each of the bindings
1575 * - `pat` is the argument pattern
1576 * - `llval` is a pointer to the argument value (in other words,
1577 * if the argument type is `T`, then `llval` is a `T*`). In some
1578 * cases, this code may zero out the memory `llval` points at.
1581 let _icx = push_ctxt("match::store_arg");
1583 match simple_identifier(&*pat) {
1585 // Generate nicer LLVM for the common case of fn a pattern
1587 let arg_ty = node_id_type(bcx, pat.id);
1588 if type_of::arg_is_indirect(bcx.ccx(), arg_ty)
1589 && bcx.sess().opts.debuginfo != FullDebugInfo {
1590 // Don't copy an indirect argument to an alloca, the caller
1591 // already put it in a temporary alloca and gave it up, unless
1592 // we emit extra-debug-info, which requires local allocas :(.
1593 let arg_val = arg.add_clean(bcx.fcx, arg_scope);
1594 bcx.fcx.llargs.borrow_mut()
1595 .insert(pat.id, Datum::new(arg_val, arg_ty, Lvalue));
1599 bcx, pat.id, ident, BindArgument, arg_scope, arg,
1600 |arg, bcx, llval, _| arg.store_to(bcx, llval))
1605 // General path. Copy out the values that are used in the
1607 let arg = unpack_datum!(
1608 bcx, arg.to_lvalue_datum_in_scope(bcx, "__arg", arg_scope));
1609 bind_irrefutable_pat(bcx, pat, arg.val,
1610 BindArgument, arg_scope)
1615 fn mk_binding_alloca<'a,A>(bcx: &'a Block<'a>,
1618 binding_mode: IrrefutablePatternBindingMode,
1619 cleanup_scope: cleanup::ScopeId,
1621 populate: |A, &'a Block<'a>, ValueRef, ty::t| -> &'a Block<'a>)
1623 let var_ty = node_id_type(bcx, p_id);
1625 // Allocate memory on stack for the binding.
1626 let llval = alloc_ty(bcx, var_ty, bcx.ident(*ident).as_slice());
1628 // Subtle: be sure that we *populate* the memory *before*
1629 // we schedule the cleanup.
1630 let bcx = populate(arg, bcx, llval, var_ty);
1631 bcx.fcx.schedule_drop_mem(cleanup_scope, llval, var_ty);
1633 // Now that memory is initialized and has cleanup scheduled,
1634 // create the datum and insert into the local variable map.
1635 let datum = Datum::new(llval, var_ty, Lvalue);
1636 let mut llmap = match binding_mode {
1637 BindLocal => bcx.fcx.lllocals.borrow_mut(),
1638 BindArgument => bcx.fcx.llargs.borrow_mut()
1640 llmap.insert(p_id, datum);
1644 fn bind_irrefutable_pat<'a>(
1648 binding_mode: IrrefutablePatternBindingMode,
1649 cleanup_scope: cleanup::ScopeId)
1652 * A simple version of the pattern matching code that only handles
1653 * irrefutable patterns. This is used in let/argument patterns,
1654 * not in match statements. Unifying this code with the code above
1655 * sounds nice, but in practice it produces very inefficient code,
1656 * since the match code is so much more general. In most cases,
1657 * LLVM is able to optimize the code, but it causes longer compile
1658 * times and makes the generated code nigh impossible to read.
1661 * - bcx: starting basic block context
1662 * - pat: the irrefutable pattern being matched.
1663 * - val: the value being matched -- must be an lvalue (by ref, with cleanup)
1664 * - binding_mode: is this for an argument or a local variable?
1667 debug!("bind_irrefutable_pat(bcx={}, pat={}, binding_mode={:?})",
1669 pat.repr(bcx.tcx()),
1672 if bcx.sess().asm_comments() {
1673 add_comment(bcx, format!("bind_irrefutable_pat(pat={})",
1674 pat.repr(bcx.tcx())).as_slice());
1677 let _indenter = indenter();
1679 let _icx = push_ctxt("match::bind_irrefutable_pat");
1681 let tcx = bcx.tcx();
1682 let ccx = bcx.ccx();
1684 ast::PatIdent(pat_binding_mode, ref path1, inner) => {
1685 if pat_is_binding(&tcx.def_map, &*pat) {
1686 // Allocate the stack slot where the value of this
1687 // binding will live and place it into the appropriate
1689 bcx = mk_binding_alloca(
1690 bcx, pat.id, &path1.node, binding_mode, cleanup_scope, (),
1691 |(), bcx, llval, ty| {
1692 match pat_binding_mode {
1693 ast::BindByValue(_) => {
1694 // By value binding: move the value that `val`
1695 // points at into the binding's stack slot.
1696 let d = Datum::new(val, ty, Lvalue);
1697 d.store_to(bcx, llval)
1700 ast::BindByRef(_) => {
1701 // By ref binding: the value of the variable
1702 // is the pointer `val` itself.
1703 Store(bcx, val, llval);
1710 for &inner_pat in inner.iter() {
1711 bcx = bind_irrefutable_pat(bcx, inner_pat, val,
1712 binding_mode, cleanup_scope);
1715 ast::PatEnum(_, ref sub_pats) => {
1716 let opt_def = bcx.tcx().def_map.borrow().find_copy(&pat.id);
1718 Some(def::DefVariant(enum_id, var_id, _)) => {
1719 let repr = adt::represent_node(bcx, pat.id);
1720 let vinfo = ty::enum_variant_with_id(ccx.tcx(),
1723 let args = extract_variant_args(bcx,
1727 for sub_pat in sub_pats.iter() {
1728 for (i, argval) in args.vals.iter().enumerate() {
1729 bcx = bind_irrefutable_pat(bcx, *sub_pat.get(i),
1730 *argval, binding_mode,
1735 Some(def::DefFn(..)) |
1736 Some(def::DefStruct(..)) => {
1739 // This is a unit-like struct. Nothing to do here.
1741 Some(ref elems) => {
1742 // This is the tuple struct case.
1743 let repr = adt::represent_node(bcx, pat.id);
1744 for (i, elem) in elems.iter().enumerate() {
1745 let fldptr = adt::trans_field_ptr(bcx, &*repr,
1747 bcx = bind_irrefutable_pat(bcx, *elem,
1748 fldptr, binding_mode,
1754 Some(def::DefStatic(_, false)) => {
1757 // Nothing to do here.
1761 ast::PatStruct(_, ref fields, _) => {
1762 let tcx = bcx.tcx();
1763 let pat_ty = node_id_type(bcx, pat.id);
1764 let pat_repr = adt::represent_type(bcx.ccx(), pat_ty);
1765 expr::with_field_tys(tcx, pat_ty, Some(pat.id), |discr, field_tys| {
1766 for f in fields.iter() {
1767 let ix = ty::field_idx_strict(tcx, f.ident.name, field_tys);
1768 let fldptr = adt::trans_field_ptr(bcx, &*pat_repr, val,
1770 bcx = bind_irrefutable_pat(bcx, f.pat, fldptr,
1771 binding_mode, cleanup_scope);
1775 ast::PatTup(ref elems) => {
1776 let repr = adt::represent_node(bcx, pat.id);
1777 for (i, elem) in elems.iter().enumerate() {
1778 let fldptr = adt::trans_field_ptr(bcx, &*repr, val, 0, i);
1779 bcx = bind_irrefutable_pat(bcx, *elem, fldptr,
1780 binding_mode, cleanup_scope);
1783 ast::PatBox(inner) => {
1784 let llbox = Load(bcx, val);
1785 bcx = bind_irrefutable_pat(bcx, inner, llbox, binding_mode, cleanup_scope);
1787 ast::PatRegion(inner) => {
1788 let loaded_val = Load(bcx, val);
1789 bcx = bind_irrefutable_pat(bcx, inner, loaded_val, binding_mode, cleanup_scope);
1791 ast::PatVec(ref before, ref slice, ref after) => {
1792 let extracted = extract_vec_elems(
1793 bcx, pat.id, before.len() + 1u + after.len(),
1794 slice.map(|_| before.len()), val
1797 .iter().map(|v| Some(*v))
1798 .chain(Some(*slice).move_iter())
1799 .chain(after.iter().map(|v| Some(*v)))
1800 .zip(extracted.vals.iter())
1801 .fold(bcx, |bcx, (inner, elem)| {
1802 inner.map_or(bcx, |inner| {
1803 bind_irrefutable_pat(bcx, inner, *elem, binding_mode, cleanup_scope)
1807 ast::PatMac(..) => {
1808 bcx.sess().span_bug(pat.span, "unexpanded macro");
1810 ast::PatWild | ast::PatWildMulti | ast::PatLit(_) | ast::PatRange(_, _) => ()