1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! # Compilation of match statements
13 //! I will endeavor to explain the code as best I can. I have only a loose
14 //! understanding of some parts of it.
18 //! The basic state of the code is maintained in an array `m` of `Match`
19 //! objects. Each `Match` describes some list of patterns, all of which must
20 //! match against the current list of values. If those patterns match, then
21 //! the arm listed in the match is the correct arm. A given arm may have
22 //! multiple corresponding match entries, one for each alternative that
23 //! remains. As we proceed these sets of matches are adjusted by the various
24 //! `enter_XXX()` functions, each of which adjusts the set of options given
25 //! some information about the value which has been matched.
27 //! So, initially, there is one value and N matches, each of which have one
28 //! constituent pattern. N here is usually the number of arms but may be
29 //! greater, if some arms have multiple alternatives. For example, here:
31 //! enum Foo { A, B(int), C(usize, usize) }
39 //! The value would be `foo`. There would be four matches, each of which
40 //! contains one pattern (and, in one case, a guard). We could collect the
41 //! various options and then compile the code for the case where `foo` is an
42 //! `A`, a `B`, and a `C`. When we generate the code for `C`, we would (1)
43 //! drop the two matches that do not match a `C` and (2) expand the other two
44 //! into two patterns each. In the first case, the two patterns would be `1`
45 //! and `2`, and the in the second case the _ pattern would be expanded into
46 //! `_` and `_`. The two values are of course the arguments to `C`.
48 //! Here is a quick guide to the various functions:
50 //! - `compile_submatch()`: The main workhouse. It takes a list of values and
51 //! a list of matches and finds the various possibilities that could occur.
53 //! - `enter_XXX()`: modifies the list of matches based on some information
54 //! about the value that has been matched. For example,
55 //! `enter_rec_or_struct()` adjusts the values given that a record or struct
56 //! has been matched. This is an infallible pattern, so *all* of the matches
57 //! must be either wildcards or record/struct patterns. `enter_opt()`
58 //! handles the fallible cases, and it is correspondingly more complex.
62 //! We store information about the bound variables for each arm as part of the
63 //! per-arm `ArmData` struct. There is a mapping from identifiers to
64 //! `BindingInfo` structs. These structs contain the mode/id/type of the
65 //! binding, but they also contain an LLVM value which points at an alloca
66 //! called `llmatch`. For by value bindings that are Copy, we also create
67 //! an extra alloca that we copy the matched value to so that any changes
68 //! we do to our copy is not reflected in the original and vice-versa.
69 //! We don't do this if it's a move since the original value can't be used
70 //! and thus allowing us to cheat in not creating an extra alloca.
72 //! The `llmatch` binding always stores a pointer into the value being matched
73 //! which points at the data for the binding. If the value being matched has
74 //! type `T`, then, `llmatch` will point at an alloca of type `T*` (and hence
75 //! `llmatch` has type `T**`). So, if you have a pattern like:
79 //! match (a, b) { (ref c, d) => { ... } }
81 //! For `c` and `d`, we would generate allocas of type `C*` and `D*`
82 //! respectively. These are called the `llmatch`. As we match, when we come
83 //! up against an identifier, we store the current pointer into the
84 //! corresponding alloca.
86 //! Once a pattern is completely matched, and assuming that there is no guard
87 //! pattern, we will branch to a block that leads to the body itself. For any
88 //! by-value bindings, this block will first load the ptr from `llmatch` (the
89 //! one of type `D*`) and then load a second time to get the actual value (the
90 //! one of type `D`). For by ref bindings, the value of the local variable is
91 //! simply the first alloca.
93 //! So, for the example above, we would generate a setup kind of like this:
99 //! +--------------------------------------------+
100 //! | llmatch_c = (addr of first half of tuple) |
101 //! | llmatch_d = (addr of second half of tuple) |
102 //! +--------------------------------------------+
104 //! +--------------------------------------+
105 //! | *llbinding_d = **llmatch_d |
106 //! +--------------------------------------+
108 //! If there is a guard, the situation is slightly different, because we must
109 //! execute the guard code. Moreover, we need to do so once for each of the
110 //! alternatives that lead to the arm, because if the guard fails, they may
111 //! have different points from which to continue the search. Therefore, in that
112 //! case, we generate code that looks more like:
118 //! +-------------------------------------------+
119 //! | llmatch_c = (addr of first half of tuple) |
120 //! | llmatch_d = (addr of first half of tuple) |
121 //! +-------------------------------------------+
123 //! +-------------------------------------------------+
124 //! | *llbinding_d = **llmatch_d |
125 //! | check condition |
126 //! | if false { goto next case } |
127 //! | if true { goto body } |
128 //! +-------------------------------------------------+
130 //! The handling for the cleanups is a bit... sensitive. Basically, the body
131 //! is the one that invokes `add_clean()` for each binding. During the guard
132 //! evaluation, we add temporary cleanups and revoke them after the guard is
133 //! evaluated (it could fail, after all). Note that guards and moves are
134 //! just plain incompatible.
136 //! Some relevant helper functions that manage bindings:
137 //! - `create_bindings_map()`
138 //! - `insert_lllocals()`
141 //! ## Notes on vector pattern matching.
143 //! Vector pattern matching is surprisingly tricky. The problem is that
144 //! the structure of the vector isn't fully known, and slice matches
145 //! can be done on subparts of it.
147 //! The way that vector pattern matches are dealt with, then, is as
148 //! follows. First, we make the actual condition associated with a
149 //! vector pattern simply a vector length comparison. So the pattern
150 //! [1, .. x] gets the condition "vec len >= 1", and the pattern
151 //! [.. x] gets the condition "vec len >= 0". The problem here is that
152 //! having the condition "vec len >= 1" hold clearly does not mean that
153 //! only a pattern that has exactly that condition will match. This
154 //! means that it may well be the case that a condition holds, but none
155 //! of the patterns matching that condition match; to deal with this,
156 //! when doing vector length matches, we have match failures proceed to
157 //! the next condition to check.
159 //! There are a couple more subtleties to deal with. While the "actual"
160 //! condition associated with vector length tests is simply a test on
161 //! the vector length, the actual vec_len Opt entry contains more
162 //! information used to restrict which matches are associated with it.
163 //! So that all matches in a submatch are matching against the same
164 //! values from inside the vector, they are split up by how many
165 //! elements they match at the front and at the back of the vector. In
166 //! order to make sure that arms are properly checked in order, even
167 //! with the overmatching conditions, each vec_len Opt entry is
168 //! associated with a range of matches.
169 //! Consider the following:
171 //! match &[1, 2, 3] {
172 //! [1, 1, .. _] => 0,
173 //! [1, 2, 2, .. _] => 1,
174 //! [1, 2, 3, .. _] => 2,
175 //! [1, 2, .. _] => 3,
178 //! The proper arm to match is arm 2, but arms 0 and 3 both have the
179 //! condition "len >= 2". If arm 3 was lumped in with arm 0, then the
180 //! wrong branch would be taken. Instead, vec_len Opts are associated
181 //! with a contiguous range of matches that have the same "shape".
182 //! This is sort of ugly and requires a bunch of special handling of
185 pub use self::BranchKind::*;
186 pub use self::OptResult::*;
187 pub use self::TransBindingMode::*;
189 use self::FailureHandler::*;
192 use llvm::{ValueRef, BasicBlockRef};
193 use middle::check_match::StaticInliner;
194 use middle::check_match;
195 use middle::const_eval;
196 use middle::def::{self, DefMap};
197 use middle::expr_use_visitor as euv;
198 use middle::lang_items::StrEqFnLangItem;
199 use middle::mem_categorization as mc;
200 use middle::pat_util::*;
203 use trans::build::{AddCase, And, Br, CondBr, GEPi, InBoundsGEP, Load, PointerCast};
204 use trans::build::{Not, Store, Sub, add_comment};
207 use trans::cleanup::{self, CleanupMethods};
208 use trans::common::*;
211 use trans::debuginfo::{self, DebugLoc, ToDebugLoc};
212 use trans::expr::{self, Dest};
215 use middle::ty::{self, Ty};
216 use session::config::{NoDebugInfo, FullDebugInfo};
217 use util::common::indenter;
218 use util::nodemap::FnvHashMap;
219 use util::ppaux::{Repr, vec_map_to_string};
222 use std::cmp::Ordering;
225 use syntax::ast::{DUMMY_NODE_ID, NodeId};
226 use syntax::codemap::Span;
227 use syntax::fold::Folder;
230 #[derive(Copy, Clone, Debug)]
231 struct ConstantExpr<'a>(&'a ast::Expr);
233 impl<'a> ConstantExpr<'a> {
234 fn eq(self, other: ConstantExpr<'a>, tcx: &ty::ctxt) -> bool {
235 match const_eval::compare_lit_exprs(tcx, self.0, other.0, None) {
236 Some(result) => result == Ordering::Equal,
237 None => panic!("compare_list_exprs: type mismatch"),
242 // An option identifying a branch (either a literal, an enum variant or a range)
245 ConstantValue(ConstantExpr<'a>, DebugLoc),
246 ConstantRange(ConstantExpr<'a>, ConstantExpr<'a>, DebugLoc),
247 Variant(ty::Disr, Rc<adt::Repr<'tcx>>, ast::DefId, DebugLoc),
248 SliceLengthEqual(usize, DebugLoc),
249 SliceLengthGreaterOrEqual(/* prefix length */ usize,
250 /* suffix length */ usize,
254 impl<'a, 'tcx> Opt<'a, 'tcx> {
255 fn eq(&self, other: &Opt<'a, 'tcx>, tcx: &ty::ctxt<'tcx>) -> bool {
256 match (self, other) {
257 (&ConstantValue(a, _), &ConstantValue(b, _)) => a.eq(b, tcx),
258 (&ConstantRange(a1, a2, _), &ConstantRange(b1, b2, _)) => {
259 a1.eq(b1, tcx) && a2.eq(b2, tcx)
261 (&Variant(a_disr, ref a_repr, a_def, _),
262 &Variant(b_disr, ref b_repr, b_def, _)) => {
263 a_disr == b_disr && *a_repr == *b_repr && a_def == b_def
265 (&SliceLengthEqual(a, _), &SliceLengthEqual(b, _)) => a == b,
266 (&SliceLengthGreaterOrEqual(a1, a2, _),
267 &SliceLengthGreaterOrEqual(b1, b2, _)) => {
274 fn trans<'blk>(&self, mut bcx: Block<'blk, 'tcx>) -> OptResult<'blk, 'tcx> {
275 let _icx = push_ctxt("match::trans_opt");
278 ConstantValue(ConstantExpr(lit_expr), _) => {
279 let lit_ty = ty::node_id_to_type(bcx.tcx(), lit_expr.id);
280 let (llval, _) = consts::const_expr(ccx, &*lit_expr, bcx.fcx.param_substs);
281 let lit_datum = immediate_rvalue(llval, lit_ty);
282 let lit_datum = unpack_datum!(bcx, lit_datum.to_appropriate_datum(bcx));
283 SingleResult(Result::new(bcx, lit_datum.val))
285 ConstantRange(ConstantExpr(ref l1), ConstantExpr(ref l2), _) => {
286 let (l1, _) = consts::const_expr(ccx, &**l1, bcx.fcx.param_substs);
287 let (l2, _) = consts::const_expr(ccx, &**l2, bcx.fcx.param_substs);
288 RangeResult(Result::new(bcx, l1), Result::new(bcx, l2))
290 Variant(disr_val, ref repr, _, _) => {
291 adt::trans_case(bcx, &**repr, disr_val)
293 SliceLengthEqual(length, _) => {
294 SingleResult(Result::new(bcx, C_uint(ccx, length)))
296 SliceLengthGreaterOrEqual(prefix, suffix, _) => {
297 LowerBound(Result::new(bcx, C_uint(ccx, prefix + suffix)))
302 fn debug_loc(&self) -> DebugLoc {
304 ConstantValue(_,debug_loc) |
305 ConstantRange(_, _, debug_loc) |
306 Variant(_, _, _, debug_loc) |
307 SliceLengthEqual(_, debug_loc) |
308 SliceLengthGreaterOrEqual(_, _, debug_loc) => debug_loc
313 #[derive(Copy, Clone, PartialEq)]
314 pub enum BranchKind {
322 pub enum OptResult<'blk, 'tcx: 'blk> {
323 SingleResult(Result<'blk, 'tcx>),
324 RangeResult(Result<'blk, 'tcx>, Result<'blk, 'tcx>),
325 LowerBound(Result<'blk, 'tcx>)
328 #[derive(Clone, Copy, PartialEq)]
329 pub enum TransBindingMode {
330 TrByCopy(/* llbinding */ ValueRef),
335 /// Information about a pattern binding:
336 /// - `llmatch` is a pointer to a stack slot. The stack slot contains a
337 /// pointer into the value being matched. Hence, llmatch has type `T**`
338 /// where `T` is the value being matched.
339 /// - `trmode` is the trans binding mode
340 /// - `id` is the node id of the binding
341 /// - `ty` is the Rust type of the binding
342 #[derive(Clone, Copy)]
343 pub struct BindingInfo<'tcx> {
344 pub llmatch: ValueRef,
345 pub trmode: TransBindingMode,
351 type BindingsMap<'tcx> = FnvHashMap<ast::Ident, BindingInfo<'tcx>>;
353 struct ArmData<'p, 'blk, 'tcx: 'blk> {
354 bodycx: Block<'blk, 'tcx>,
356 bindings_map: BindingsMap<'tcx>
359 /// Info about Match.
360 /// If all `pats` are matched then arm `data` will be executed.
361 /// As we proceed `bound_ptrs` are filled with pointers to values to be bound,
362 /// these pointers are stored in llmatch variables just before executing `data` arm.
363 struct Match<'a, 'p: 'a, 'blk: 'a, 'tcx: 'blk> {
364 pats: Vec<&'p ast::Pat>,
365 data: &'a ArmData<'p, 'blk, 'tcx>,
366 bound_ptrs: Vec<(ast::Ident, ValueRef)>,
367 // Thread along renamings done by the check_match::StaticInliner, so we can
368 // map back to original NodeIds
369 pat_renaming_map: Option<&'a FnvHashMap<(NodeId, Span), NodeId>>
372 impl<'a, 'p, 'blk, 'tcx> Repr<'tcx> for Match<'a, 'p, 'blk, 'tcx> {
373 fn repr(&self, tcx: &ty::ctxt) -> String {
374 if tcx.sess.verbose() {
375 // for many programs, this just take too long to serialize
378 format!("{} pats", self.pats.len())
383 fn has_nested_bindings(m: &[Match], col: usize) -> bool {
385 match br.pats[col].node {
386 ast::PatIdent(_, _, Some(_)) => return true,
393 fn expand_nested_bindings<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
394 m: &[Match<'a, 'p, 'blk, 'tcx>],
397 -> Vec<Match<'a, 'p, 'blk, 'tcx>> {
398 debug!("expand_nested_bindings(bcx={}, m={}, col={}, val={})",
402 bcx.val_to_string(val));
403 let _indenter = indenter();
406 let mut bound_ptrs = br.bound_ptrs.clone();
407 let mut pat = br.pats[col];
409 pat = match pat.node {
410 ast::PatIdent(_, ref path, Some(ref inner)) => {
411 bound_ptrs.push((path.node, val));
418 let mut pats = br.pats.clone();
423 bound_ptrs: bound_ptrs,
424 pat_renaming_map: br.pat_renaming_map,
429 fn enter_match<'a, 'b, 'p, 'blk, 'tcx, F>(bcx: Block<'blk, 'tcx>,
431 m: &[Match<'a, 'p, 'blk, 'tcx>],
435 -> Vec<Match<'a, 'p, 'blk, 'tcx>> where
436 F: FnMut(&[&'p ast::Pat]) -> Option<Vec<&'p ast::Pat>>,
438 debug!("enter_match(bcx={}, m={}, col={}, val={})",
442 bcx.val_to_string(val));
443 let _indenter = indenter();
445 m.iter().filter_map(|br| {
446 e(&br.pats).map(|pats| {
447 let this = br.pats[col];
448 let mut bound_ptrs = br.bound_ptrs.clone();
450 ast::PatIdent(_, ref path, None) => {
451 if pat_is_binding(dm, &*this) {
452 bound_ptrs.push((path.node, val));
455 ast::PatVec(ref before, Some(ref slice), ref after) => {
456 if let ast::PatIdent(_, ref path, None) = slice.node {
457 let subslice_val = bind_subslice_pat(
459 before.len(), after.len());
460 bound_ptrs.push((path.node, subslice_val));
468 bound_ptrs: bound_ptrs,
469 pat_renaming_map: br.pat_renaming_map,
475 fn enter_default<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
477 m: &[Match<'a, 'p, 'blk, 'tcx>],
480 -> Vec<Match<'a, 'p, 'blk, 'tcx>> {
481 debug!("enter_default(bcx={}, m={}, col={}, val={})",
485 bcx.val_to_string(val));
486 let _indenter = indenter();
488 // Collect all of the matches that can match against anything.
489 enter_match(bcx, dm, m, col, val, |pats| {
490 if pat_is_binding_or_wild(dm, &*pats[col]) {
491 let mut r = pats[..col].to_vec();
492 r.push_all(&pats[col + 1..]);
500 // <pcwalton> nmatsakis: what does enter_opt do?
501 // <pcwalton> in trans/match
502 // <pcwalton> trans/match.rs is like stumbling around in a dark cave
503 // <nmatsakis> pcwalton: the enter family of functions adjust the set of
504 // patterns as needed
505 // <nmatsakis> yeah, at some point I kind of achieved some level of
507 // <nmatsakis> anyhow, they adjust the patterns given that something of that
508 // kind has been found
509 // <nmatsakis> pcwalton: ok, right, so enter_XXX() adjusts the patterns, as I
511 // <nmatsakis> enter_match() kind of embodies the generic code
512 // <nmatsakis> it is provided with a function that tests each pattern to see
513 // if it might possibly apply and so forth
514 // <nmatsakis> so, if you have a pattern like {a: _, b: _, _} and one like _
515 // <nmatsakis> then _ would be expanded to (_, _)
516 // <nmatsakis> one spot for each of the sub-patterns
517 // <nmatsakis> enter_opt() is one of the more complex; it covers the fallible
519 // <nmatsakis> enter_rec_or_struct() or enter_tuple() are simpler, since they
520 // are infallible patterns
521 // <nmatsakis> so all patterns must either be records (resp. tuples) or
524 /// The above is now outdated in that enter_match() now takes a function that
525 /// takes the complete row of patterns rather than just the first one.
526 /// Also, most of the enter_() family functions have been unified with
527 /// the check_match specialization step.
528 fn enter_opt<'a, 'p, 'blk, 'tcx>(
529 bcx: Block<'blk, 'tcx>,
532 m: &[Match<'a, 'p, 'blk, 'tcx>],
537 -> Vec<Match<'a, 'p, 'blk, 'tcx>> {
538 debug!("enter_opt(bcx={}, m={}, opt={:?}, col={}, val={})",
543 bcx.val_to_string(val));
544 let _indenter = indenter();
546 let ctor = match opt {
547 &ConstantValue(ConstantExpr(expr), _) => check_match::ConstantValue(
548 const_eval::eval_const_expr(bcx.tcx(), &*expr)
550 &ConstantRange(ConstantExpr(lo), ConstantExpr(hi), _) => check_match::ConstantRange(
551 const_eval::eval_const_expr(bcx.tcx(), &*lo),
552 const_eval::eval_const_expr(bcx.tcx(), &*hi)
554 &SliceLengthEqual(n, _) =>
555 check_match::Slice(n),
556 &SliceLengthGreaterOrEqual(before, after, _) =>
557 check_match::SliceWithSubslice(before, after),
558 &Variant(_, _, def_id, _) =>
559 check_match::Constructor::Variant(def_id)
562 let param_env = ty::empty_parameter_environment(bcx.tcx());
563 let mcx = check_match::MatchCheckCtxt {
565 param_env: param_env,
567 enter_match(bcx, dm, m, col, val, |pats|
568 check_match::specialize(&mcx, &pats[..], &ctor, col, variant_size)
572 // Returns the options in one column of matches. An option is something that
573 // needs to be conditionally matched at runtime; for example, the discriminant
574 // on a set of enum variants or a literal.
575 fn get_branches<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
576 m: &[Match<'a, 'p, 'blk, 'tcx>],
578 -> Vec<Opt<'p, 'tcx>> {
581 let mut found: Vec<Opt> = vec![];
583 let cur = br.pats[col];
584 let debug_loc = match br.pat_renaming_map {
585 Some(pat_renaming_map) => {
586 match pat_renaming_map.get(&(cur.id, cur.span)) {
587 Some(&id) => DebugLoc::At(id, cur.span),
588 None => DebugLoc::At(cur.id, cur.span),
591 None => DebugLoc::None
594 let opt = match cur.node {
595 ast::PatLit(ref l) => {
596 ConstantValue(ConstantExpr(&**l), debug_loc)
598 ast::PatIdent(..) | ast::PatEnum(..) | ast::PatStruct(..) => {
599 // This is either an enum variant or a variable binding.
600 let opt_def = tcx.def_map.borrow().get(&cur.id).map(|d| d.full_def());
602 Some(def::DefVariant(enum_id, var_id, _)) => {
603 let variant = ty::enum_variant_with_id(tcx, enum_id, var_id);
604 Variant(variant.disr_val,
605 adt::represent_node(bcx, cur.id),
612 ast::PatRange(ref l1, ref l2) => {
613 ConstantRange(ConstantExpr(&**l1), ConstantExpr(&**l2), debug_loc)
615 ast::PatVec(ref before, None, ref after) => {
616 SliceLengthEqual(before.len() + after.len(), debug_loc)
618 ast::PatVec(ref before, Some(_), ref after) => {
619 SliceLengthGreaterOrEqual(before.len(), after.len(), debug_loc)
624 if !found.iter().any(|x| x.eq(&opt, tcx)) {
631 struct ExtractedBlock<'blk, 'tcx: 'blk> {
633 bcx: Block<'blk, 'tcx>,
636 fn extract_variant_args<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
637 repr: &adt::Repr<'tcx>,
640 -> ExtractedBlock<'blk, 'tcx> {
641 let _icx = push_ctxt("match::extract_variant_args");
642 let args = (0..adt::num_args(repr, disr_val)).map(|i| {
643 adt::trans_field_ptr(bcx, repr, val, disr_val, i)
646 ExtractedBlock { vals: args, bcx: bcx }
649 /// Helper for converting from the ValueRef that we pass around in the match code, which is always
650 /// an lvalue, into a Datum. Eventually we should just pass around a Datum and be done with it.
651 fn match_datum<'tcx>(val: ValueRef, left_ty: Ty<'tcx>) -> Datum<'tcx, Lvalue> {
652 Datum::new(val, left_ty, Lvalue)
655 fn bind_subslice_pat(bcx: Block,
659 offset_right: usize) -> ValueRef {
660 let _icx = push_ctxt("match::bind_subslice_pat");
661 let vec_ty = node_id_type(bcx, pat_id);
662 let unit_ty = ty::sequence_element_type(bcx.tcx(), ty::type_content(vec_ty));
663 let vec_datum = match_datum(val, vec_ty);
664 let (base, len) = vec_datum.get_vec_base_and_len(bcx);
666 let slice_begin = InBoundsGEP(bcx, base, &[C_uint(bcx.ccx(), offset_left)]);
667 let slice_len_offset = C_uint(bcx.ccx(), offset_left + offset_right);
668 let slice_len = Sub(bcx, len, slice_len_offset, DebugLoc::None);
669 let slice_ty = ty::mk_slice(bcx.tcx(),
670 bcx.tcx().mk_region(ty::ReStatic),
671 ty::mt {ty: unit_ty, mutbl: ast::MutImmutable});
672 let scratch = rvalue_scratch_datum(bcx, slice_ty, "");
673 Store(bcx, slice_begin,
674 GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_ADDR]));
675 Store(bcx, slice_len, GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_EXTRA]));
679 fn extract_vec_elems<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
684 -> ExtractedBlock<'blk, 'tcx> {
685 let _icx = push_ctxt("match::extract_vec_elems");
686 let vec_datum = match_datum(val, left_ty);
687 let (base, len) = vec_datum.get_vec_base_and_len(bcx);
688 let mut elems = vec![];
689 elems.extend((0..before).map(|i| GEPi(bcx, base, &[i])));
690 elems.extend((0..after).rev().map(|i| {
691 InBoundsGEP(bcx, base, &[
692 Sub(bcx, len, C_uint(bcx.ccx(), i + 1), DebugLoc::None)
695 ExtractedBlock { vals: elems, bcx: bcx }
698 // Macro for deciding whether any of the remaining matches fit a given kind of
699 // pattern. Note that, because the macro is well-typed, either ALL of the
700 // matches should fit that sort of pattern or NONE (however, some of the
701 // matches may be wildcards like _ or identifiers).
702 macro_rules! any_pat {
703 ($m:expr, $col:expr, $pattern:pat) => (
704 ($m).iter().any(|br| {
705 match br.pats[$col].node {
713 fn any_uniq_pat(m: &[Match], col: usize) -> bool {
714 any_pat!(m, col, ast::PatBox(_))
717 fn any_region_pat(m: &[Match], col: usize) -> bool {
718 any_pat!(m, col, ast::PatRegion(..))
721 fn any_irrefutable_adt_pat(tcx: &ty::ctxt, m: &[Match], col: usize) -> bool {
723 let pat = br.pats[col];
725 ast::PatTup(_) => true,
726 ast::PatStruct(..) => {
727 match tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()) {
728 Some(def::DefVariant(..)) => false,
732 ast::PatEnum(..) | ast::PatIdent(_, _, None) => {
733 match tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()) {
734 Some(def::DefStruct(..)) => true,
743 /// What to do when the pattern match fails.
744 enum FailureHandler {
746 JumpToBasicBlock(BasicBlockRef),
750 impl FailureHandler {
751 fn is_fallible(&self) -> bool {
758 fn is_infallible(&self) -> bool {
762 fn handle_fail(&self, bcx: Block) {
765 panic!("attempted to panic in a non-panicking panic handler!"),
766 JumpToBasicBlock(basic_block) =>
767 Br(bcx, basic_block, DebugLoc::None),
769 build::Unreachable(bcx)
774 fn pick_column_to_specialize(def_map: &DefMap, m: &[Match]) -> Option<usize> {
775 fn pat_score(def_map: &DefMap, pat: &ast::Pat) -> usize {
777 ast::PatIdent(_, _, Some(ref inner)) => pat_score(def_map, &**inner),
778 _ if pat_is_refutable(def_map, pat) => 1,
783 let column_score = |m: &[Match], col: usize| -> usize {
784 let total_score = m.iter()
785 .map(|row| row.pats[col])
786 .map(|pat| pat_score(def_map, pat))
789 // Irrefutable columns always go first, they'd only be duplicated in the branches.
790 if total_score == 0 {
797 let column_contains_any_nonwild_patterns = |&col: &usize| -> bool {
798 m.iter().any(|row| match row.pats[col].node {
799 ast::PatWild(_) => false,
805 .filter(column_contains_any_nonwild_patterns)
806 .map(|col| (col, column_score(m, col)))
807 .max_by(|&(_, score)| score)
811 // Compiles a comparison between two things.
812 fn compare_values<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
817 -> Result<'blk, 'tcx> {
818 fn compare_str<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
823 -> Result<'blk, 'tcx> {
824 let did = langcall(cx,
826 &format!("comparison of `{}`",
827 cx.ty_to_string(rhs_t)),
829 let t = ty::mk_str_slice(cx.tcx(), cx.tcx().mk_region(ty::ReStatic), ast::MutImmutable);
830 // The comparison function gets the slices by value, so we have to make copies here. Even
831 // if the function doesn't write through the pointer, things like lifetime intrinsics
832 // require that we do this properly
833 let lhs_arg = alloc_ty(cx, t, "lhs");
834 let rhs_arg = alloc_ty(cx, t, "rhs");
835 memcpy_ty(cx, lhs_arg, lhs, t);
836 memcpy_ty(cx, rhs_arg, rhs, t);
837 let res = callee::trans_lang_call(cx, did, &[lhs_arg, rhs_arg], None, debug_loc);
838 call_lifetime_end(res.bcx, lhs_arg);
839 call_lifetime_end(res.bcx, rhs_arg);
844 let _icx = push_ctxt("compare_values");
845 if ty::type_is_scalar(rhs_t) {
846 let cmp = compare_scalar_types(cx, lhs, rhs, rhs_t, ast::BiEq, debug_loc);
847 return Result::new(cx, cmp);
851 ty::ty_rptr(_, mt) => match mt.ty.sty {
852 ty::ty_str => compare_str(cx, lhs, rhs, rhs_t, debug_loc),
853 ty::ty_vec(ty, _) => match ty.sty {
854 ty::ty_uint(ast::TyU8) => {
855 // NOTE: cast &[u8] and &[u8; N] to &str and abuse the str_eq lang item,
856 // which calls memcmp().
857 let pat_len = val_ty(rhs).element_type().array_length();
858 let ty_str_slice = ty::mk_str_slice(cx.tcx(),
859 cx.tcx().mk_region(ty::ReStatic),
862 let rhs_str = alloc_ty(cx, ty_str_slice, "rhs_str");
863 Store(cx, GEPi(cx, rhs, &[0, 0]), expr::get_dataptr(cx, rhs_str));
864 Store(cx, C_uint(cx.ccx(), pat_len), expr::get_len(cx, rhs_str));
867 if val_ty(lhs) == val_ty(rhs) {
868 // Both the discriminant and the pattern are thin pointers
869 lhs_str = alloc_ty(cx, ty_str_slice, "lhs_str");
870 Store(cx, GEPi(cx, lhs, &[0, 0]), expr::get_dataptr(cx, lhs_str));
871 Store(cx, C_uint(cx.ccx(), pat_len), expr::get_len(cx, lhs_str));
874 // The discriminant is a fat pointer
875 let llty_str_slice = type_of::type_of(cx.ccx(), ty_str_slice).ptr_to();
876 lhs_str = PointerCast(cx, lhs, llty_str_slice);
879 compare_str(cx, lhs_str, rhs_str, rhs_t, debug_loc)
881 _ => cx.sess().bug("only byte strings supported in compare_values"),
883 _ => cx.sess().bug("only string and byte strings supported in compare_values"),
885 _ => cx.sess().bug("only scalars, byte strings, and strings supported in compare_values"),
889 /// For each binding in `data.bindings_map`, adds an appropriate entry into the `fcx.lllocals` map
890 fn insert_lllocals<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
891 bindings_map: &BindingsMap<'tcx>,
892 cs: Option<cleanup::ScopeId>)
893 -> Block<'blk, 'tcx> {
894 for (&ident, &binding_info) in bindings_map {
895 let llval = match binding_info.trmode {
896 // By value mut binding for a copy type: load from the ptr
897 // into the matched value and copy to our alloca
898 TrByCopy(llbinding) => {
899 let llval = Load(bcx, binding_info.llmatch);
900 let datum = Datum::new(llval, binding_info.ty, Lvalue);
901 call_lifetime_start(bcx, llbinding);
902 bcx = datum.store_to(bcx, llbinding);
903 if let Some(cs) = cs {
904 bcx.fcx.schedule_lifetime_end(cs, llbinding);
910 // By value move bindings: load from the ptr into the matched value
911 TrByMove => Load(bcx, binding_info.llmatch),
913 // By ref binding: use the ptr into the matched value
914 TrByRef => binding_info.llmatch
917 let datum = Datum::new(llval, binding_info.ty, Lvalue);
918 if let Some(cs) = cs {
919 bcx.fcx.schedule_lifetime_end(cs, binding_info.llmatch);
920 bcx.fcx.schedule_drop_and_fill_mem(cs, llval, binding_info.ty);
923 debug!("binding {} to {}", binding_info.id, bcx.val_to_string(llval));
924 bcx.fcx.lllocals.borrow_mut().insert(binding_info.id, datum);
925 debuginfo::create_match_binding_metadata(bcx, ident.name, binding_info);
930 fn compile_guard<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
931 guard_expr: &ast::Expr,
932 data: &ArmData<'p, 'blk, 'tcx>,
933 m: &[Match<'a, 'p, 'blk, 'tcx>],
935 chk: &FailureHandler,
936 has_genuine_default: bool)
937 -> Block<'blk, 'tcx> {
938 debug!("compile_guard(bcx={}, guard_expr={}, m={}, vals={})",
940 bcx.expr_to_string(guard_expr),
942 vec_map_to_string(vals, |v| bcx.val_to_string(*v)));
943 let _indenter = indenter();
945 let mut bcx = insert_lllocals(bcx, &data.bindings_map, None);
947 let val = unpack_datum!(bcx, expr::trans(bcx, guard_expr));
948 let val = val.to_llbool(bcx);
950 for (_, &binding_info) in &data.bindings_map {
951 if let TrByCopy(llbinding) = binding_info.trmode {
952 call_lifetime_end(bcx, llbinding);
956 for (_, &binding_info) in &data.bindings_map {
957 bcx.fcx.lllocals.borrow_mut().remove(&binding_info.id);
960 with_cond(bcx, Not(bcx, val, guard_expr.debug_loc()), |bcx| {
961 for (_, &binding_info) in &data.bindings_map {
962 call_lifetime_end(bcx, binding_info.llmatch);
965 // If the default arm is the only one left, move on to the next
966 // condition explicitly rather than (possibly) falling back to
968 &JumpToBasicBlock(_) if m.len() == 1 && has_genuine_default => {
969 chk.handle_fail(bcx);
972 compile_submatch(bcx, m, vals, chk, has_genuine_default);
979 fn compile_submatch<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
980 m: &[Match<'a, 'p, 'blk, 'tcx>],
982 chk: &FailureHandler,
983 has_genuine_default: bool) {
984 debug!("compile_submatch(bcx={}, m={}, vals={})",
987 vec_map_to_string(vals, |v| bcx.val_to_string(*v)));
988 let _indenter = indenter();
989 let _icx = push_ctxt("match::compile_submatch");
992 if chk.is_fallible() {
993 chk.handle_fail(bcx);
999 let def_map = &tcx.def_map;
1000 match pick_column_to_specialize(def_map, m) {
1002 let val = vals[col];
1003 if has_nested_bindings(m, col) {
1004 let expanded = expand_nested_bindings(bcx, m, col, val);
1005 compile_submatch_continue(bcx,
1011 has_genuine_default)
1013 compile_submatch_continue(bcx, m, vals, chk, col, val, has_genuine_default)
1017 let data = &m[0].data;
1018 for &(ref ident, ref value_ptr) in &m[0].bound_ptrs {
1019 let binfo = *data.bindings_map.get(ident).unwrap();
1020 call_lifetime_start(bcx, binfo.llmatch);
1021 if binfo.trmode == TrByRef && type_is_fat_ptr(bcx.tcx(), binfo.ty) {
1022 expr::copy_fat_ptr(bcx, *value_ptr, binfo.llmatch);
1025 Store(bcx, *value_ptr, binfo.llmatch);
1028 match data.arm.guard {
1029 Some(ref guard_expr) => {
1030 bcx = compile_guard(bcx,
1036 has_genuine_default);
1040 Br(bcx, data.bodycx.llbb, DebugLoc::None);
1045 fn compile_submatch_continue<'a, 'p, 'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
1046 m: &[Match<'a, 'p, 'blk, 'tcx>],
1048 chk: &FailureHandler,
1051 has_genuine_default: bool) {
1053 let tcx = bcx.tcx();
1054 let dm = &tcx.def_map;
1056 let mut vals_left = vals[0..col].to_vec();
1057 vals_left.push_all(&vals[col + 1..]);
1058 let ccx = bcx.fcx.ccx;
1060 // Find a real id (we're adding placeholder wildcard patterns, but
1061 // each column is guaranteed to have at least one real pattern)
1062 let pat_id = m.iter().map(|br| br.pats[col].id)
1063 .find(|&id| id != DUMMY_NODE_ID)
1064 .unwrap_or(DUMMY_NODE_ID);
1066 let left_ty = if pat_id == DUMMY_NODE_ID {
1069 node_id_type(bcx, pat_id)
1072 let mcx = check_match::MatchCheckCtxt {
1074 param_env: ty::empty_parameter_environment(bcx.tcx()),
1076 let adt_vals = if any_irrefutable_adt_pat(bcx.tcx(), m, col) {
1077 let repr = adt::represent_type(bcx.ccx(), left_ty);
1078 let arg_count = adt::num_args(&*repr, 0);
1079 let field_vals: Vec<ValueRef> = (0..arg_count).map(|ix|
1080 adt::trans_field_ptr(bcx, &*repr, val, 0, ix)
1083 } else if any_uniq_pat(m, col) || any_region_pat(m, col) {
1084 Some(vec!(Load(bcx, val)))
1087 ty::ty_vec(_, Some(n)) => {
1088 let args = extract_vec_elems(bcx, left_ty, n, 0, val);
1095 Some(field_vals) => {
1096 let pats = enter_match(bcx, dm, m, col, val, |pats|
1097 check_match::specialize(&mcx, pats,
1098 &check_match::Single, col,
1101 let mut vals = field_vals;
1102 vals.push_all(&vals_left);
1103 compile_submatch(bcx, &pats, &vals, chk, has_genuine_default);
1109 // Decide what kind of branch we need
1110 let opts = get_branches(bcx, m, col);
1111 debug!("options={:?}", opts);
1112 let mut kind = NoBranch;
1113 let mut test_val = val;
1114 debug!("test_val={}", bcx.val_to_string(test_val));
1115 if !opts.is_empty() {
1117 ConstantValue(..) | ConstantRange(..) => {
1118 test_val = load_if_immediate(bcx, val, left_ty);
1119 kind = if ty::type_is_integral(left_ty) {
1125 Variant(_, ref repr, _, _) => {
1126 let (the_kind, val_opt) = adt::trans_switch(bcx, &**repr, val);
1128 if let Some(tval) = val_opt { test_val = tval; }
1130 SliceLengthEqual(..) | SliceLengthGreaterOrEqual(..) => {
1131 let (_, len) = tvec::get_base_and_len(bcx, val, left_ty);
1139 ConstantRange(..) => { kind = Compare; break },
1140 SliceLengthGreaterOrEqual(..) => { kind = CompareSliceLength; break },
1144 let else_cx = match kind {
1145 NoBranch | Single => bcx,
1146 _ => bcx.fcx.new_temp_block("match_else")
1148 let sw = if kind == Switch {
1149 build::Switch(bcx, test_val, else_cx.llbb, opts.len())
1151 C_int(ccx, 0) // Placeholder for when not using a switch
1154 let defaults = enter_default(else_cx, dm, m, col, val);
1155 let exhaustive = chk.is_infallible() && defaults.is_empty();
1156 let len = opts.len();
1158 // Compile subtrees for each option
1159 for (i, opt) in opts.iter().enumerate() {
1160 // In some cases of range and vector pattern matching, we need to
1161 // override the failure case so that instead of failing, it proceeds
1162 // to try more matching. branch_chk, then, is the proper failure case
1163 // for the current conditional branch.
1164 let mut branch_chk = None;
1165 let mut opt_cx = else_cx;
1166 let debug_loc = opt.debug_loc();
1168 if !exhaustive || i + 1 < len {
1169 opt_cx = bcx.fcx.new_temp_block("match_case");
1171 Single => Br(bcx, opt_cx.llbb, debug_loc),
1173 match opt.trans(bcx) {
1174 SingleResult(r) => {
1175 AddCase(sw, r.val, opt_cx.llbb);
1180 "in compile_submatch, expected \
1181 opt.trans() to return a SingleResult")
1185 Compare | CompareSliceLength => {
1186 let t = if kind == Compare {
1189 tcx.types.usize // vector length
1191 let Result { bcx: after_cx, val: matches } = {
1192 match opt.trans(bcx) {
1193 SingleResult(Result { bcx, val }) => {
1194 compare_values(bcx, test_val, val, t, debug_loc)
1196 RangeResult(Result { val: vbegin, .. },
1197 Result { bcx, val: vend }) => {
1198 let llge = compare_scalar_types(bcx, test_val, vbegin,
1199 t, ast::BiGe, debug_loc);
1200 let llle = compare_scalar_types(bcx, test_val, vend,
1201 t, ast::BiLe, debug_loc);
1202 Result::new(bcx, And(bcx, llge, llle, DebugLoc::None))
1204 LowerBound(Result { bcx, val }) => {
1205 Result::new(bcx, compare_scalar_types(bcx, test_val,
1211 bcx = fcx.new_temp_block("compare_next");
1213 // If none of the sub-cases match, and the current condition
1214 // is guarded or has multiple patterns, move on to the next
1215 // condition, if there is any, rather than falling back to
1217 let guarded = m[i].data.arm.guard.is_some();
1218 let multi_pats = m[i].pats.len() > 1;
1219 if i + 1 < len && (guarded || multi_pats || kind == CompareSliceLength) {
1220 branch_chk = Some(JumpToBasicBlock(bcx.llbb));
1222 CondBr(after_cx, matches, opt_cx.llbb, bcx.llbb, debug_loc);
1226 } else if kind == Compare || kind == CompareSliceLength {
1227 Br(bcx, else_cx.llbb, debug_loc);
1231 let mut unpacked = Vec::new();
1233 Variant(disr_val, ref repr, _, _) => {
1234 let ExtractedBlock {vals: argvals, bcx: new_bcx} =
1235 extract_variant_args(opt_cx, &**repr, disr_val, val);
1236 size = argvals.len();
1240 SliceLengthEqual(len, _) => {
1241 let args = extract_vec_elems(opt_cx, left_ty, len, 0, val);
1242 size = args.vals.len();
1243 unpacked = args.vals.clone();
1246 SliceLengthGreaterOrEqual(before, after, _) => {
1247 let args = extract_vec_elems(opt_cx, left_ty, before, after, val);
1248 size = args.vals.len();
1249 unpacked = args.vals.clone();
1252 ConstantValue(..) | ConstantRange(..) => ()
1254 let opt_ms = enter_opt(opt_cx, pat_id, dm, m, opt, col, size, val);
1255 let mut opt_vals = unpacked;
1256 opt_vals.push_all(&vals_left[..]);
1257 compile_submatch(opt_cx,
1260 branch_chk.as_ref().unwrap_or(chk),
1261 has_genuine_default);
1264 // Compile the fall-through case, if any
1265 if !exhaustive && kind != Single {
1266 if kind == Compare || kind == CompareSliceLength {
1267 Br(bcx, else_cx.llbb, DebugLoc::None);
1270 // If there is only one default arm left, move on to the next
1271 // condition explicitly rather than (eventually) falling back to
1272 // the last default arm.
1273 &JumpToBasicBlock(_) if defaults.len() == 1 && has_genuine_default => {
1274 chk.handle_fail(else_cx);
1277 compile_submatch(else_cx,
1281 has_genuine_default);
1287 pub fn trans_match<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
1288 match_expr: &ast::Expr,
1289 discr_expr: &ast::Expr,
1292 -> Block<'blk, 'tcx> {
1293 let _icx = push_ctxt("match::trans_match");
1294 trans_match_inner(bcx, match_expr.id, discr_expr, arms, dest)
1297 /// Checks whether the binding in `discr` is assigned to anywhere in the expression `body`
1298 fn is_discr_reassigned(bcx: Block, discr: &ast::Expr, body: &ast::Expr) -> bool {
1299 let (vid, field) = match discr.node {
1300 ast::ExprPath(..) => match bcx.def(discr.id) {
1301 def::DefLocal(vid) | def::DefUpvar(vid, _) => (vid, None),
1304 ast::ExprField(ref base, field) => {
1305 let vid = match bcx.tcx().def_map.borrow().get(&base.id).map(|d| d.full_def()) {
1306 Some(def::DefLocal(vid)) | Some(def::DefUpvar(vid, _)) => vid,
1309 (vid, Some(mc::NamedField(field.node.name)))
1311 ast::ExprTupField(ref base, field) => {
1312 let vid = match bcx.tcx().def_map.borrow().get(&base.id).map(|d| d.full_def()) {
1313 Some(def::DefLocal(vid)) | Some(def::DefUpvar(vid, _)) => vid,
1316 (vid, Some(mc::PositionalField(field.node)))
1321 let mut rc = ReassignmentChecker {
1327 let mut visitor = euv::ExprUseVisitor::new(&mut rc, bcx);
1328 visitor.walk_expr(body);
1333 struct ReassignmentChecker {
1335 field: Option<mc::FieldName>,
1339 // Determine if the expression we're matching on is reassigned to within
1340 // the body of the match's arm.
1341 // We only care for the `mutate` callback since this check only matters
1342 // for cases where the matched value is moved.
1343 impl<'tcx> euv::Delegate<'tcx> for ReassignmentChecker {
1344 fn consume(&mut self, _: ast::NodeId, _: Span, _: mc::cmt, _: euv::ConsumeMode) {}
1345 fn matched_pat(&mut self, _: &ast::Pat, _: mc::cmt, _: euv::MatchMode) {}
1346 fn consume_pat(&mut self, _: &ast::Pat, _: mc::cmt, _: euv::ConsumeMode) {}
1347 fn borrow(&mut self, _: ast::NodeId, _: Span, _: mc::cmt, _: ty::Region,
1348 _: ty::BorrowKind, _: euv::LoanCause) {}
1349 fn decl_without_init(&mut self, _: ast::NodeId, _: Span) {}
1351 fn mutate(&mut self, _: ast::NodeId, _: Span, cmt: mc::cmt, _: euv::MutateMode) {
1353 mc::cat_upvar(mc::Upvar { id: ty::UpvarId { var_id: vid, .. }, .. }) |
1354 mc::cat_local(vid) => self.reassigned |= self.node == vid,
1355 mc::cat_interior(ref base_cmt, mc::InteriorField(field)) => {
1356 match base_cmt.cat {
1357 mc::cat_upvar(mc::Upvar { id: ty::UpvarId { var_id: vid, .. }, .. }) |
1358 mc::cat_local(vid) => {
1359 self.reassigned |= self.node == vid && Some(field) == self.field
1369 fn create_bindings_map<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, pat: &ast::Pat,
1370 discr: &ast::Expr, body: &ast::Expr)
1371 -> BindingsMap<'tcx> {
1372 // Create the bindings map, which is a mapping from each binding name
1373 // to an alloca() that will be the value for that local variable.
1374 // Note that we use the names because each binding will have many ids
1375 // from the various alternatives.
1376 let ccx = bcx.ccx();
1377 let tcx = bcx.tcx();
1378 let reassigned = is_discr_reassigned(bcx, discr, body);
1379 let mut bindings_map = FnvHashMap();
1380 pat_bindings(&tcx.def_map, &*pat, |bm, p_id, span, path1| {
1381 let ident = path1.node;
1382 let name = ident.name;
1383 let variable_ty = node_id_type(bcx, p_id);
1384 let llvariable_ty = type_of::type_of(ccx, variable_ty);
1385 let tcx = bcx.tcx();
1386 let param_env = ty::empty_parameter_environment(tcx);
1392 if !ty::type_moves_by_default(¶m_env, span, variable_ty) || reassigned =>
1394 llmatch = alloca_no_lifetime(bcx,
1395 llvariable_ty.ptr_to(),
1397 trmode = TrByCopy(alloca_no_lifetime(bcx,
1401 ast::BindByValue(_) => {
1402 // in this case, the final type of the variable will be T,
1403 // but during matching we need to store a *T as explained
1405 llmatch = alloca_no_lifetime(bcx,
1406 llvariable_ty.ptr_to(),
1410 ast::BindByRef(_) => {
1411 llmatch = alloca_no_lifetime(bcx,
1417 bindings_map.insert(ident, BindingInfo {
1425 return bindings_map;
1428 fn trans_match_inner<'blk, 'tcx>(scope_cx: Block<'blk, 'tcx>,
1429 match_id: ast::NodeId,
1430 discr_expr: &ast::Expr,
1432 dest: Dest) -> Block<'blk, 'tcx> {
1433 let _icx = push_ctxt("match::trans_match_inner");
1434 let fcx = scope_cx.fcx;
1435 let mut bcx = scope_cx;
1436 let tcx = bcx.tcx();
1438 let discr_datum = unpack_datum!(bcx, expr::trans_to_lvalue(bcx, discr_expr,
1440 if bcx.unreachable.get() {
1444 let t = node_id_type(bcx, discr_expr.id);
1445 let chk = if ty::type_is_empty(tcx, t) {
1451 let arm_datas: Vec<ArmData> = arms.iter().map(|arm| ArmData {
1452 bodycx: fcx.new_id_block("case_body", arm.body.id),
1454 bindings_map: create_bindings_map(bcx, &*arm.pats[0], discr_expr, &*arm.body)
1457 let mut pat_renaming_map = if scope_cx.sess().opts.debuginfo != NoDebugInfo {
1463 let arm_pats: Vec<Vec<P<ast::Pat>>> = {
1464 let mut static_inliner = StaticInliner::new(scope_cx.tcx(),
1465 pat_renaming_map.as_mut());
1466 arm_datas.iter().map(|arm_data| {
1467 arm_data.arm.pats.iter().map(|p| static_inliner.fold_pat((*p).clone())).collect()
1471 let mut matches = Vec::new();
1472 for (arm_data, pats) in arm_datas.iter().zip(arm_pats.iter()) {
1473 matches.extend(pats.iter().map(|p| Match {
1476 bound_ptrs: Vec::new(),
1477 pat_renaming_map: pat_renaming_map.as_ref()
1481 // `compile_submatch` works one column of arm patterns a time and
1482 // then peels that column off. So as we progress, it may become
1483 // impossible to tell whether we have a genuine default arm, i.e.
1484 // `_ => foo` or not. Sometimes it is important to know that in order
1485 // to decide whether moving on to the next condition or falling back
1486 // to the default arm.
1487 let has_default = arms.last().map_or(false, |arm| {
1489 && arm.pats.last().unwrap().node == ast::PatWild(ast::PatWildSingle)
1492 compile_submatch(bcx, &matches[..], &[discr_datum.val], &chk, has_default);
1494 let mut arm_cxs = Vec::new();
1495 for arm_data in &arm_datas {
1496 let mut bcx = arm_data.bodycx;
1498 // insert bindings into the lllocals map and add cleanups
1499 let cs = fcx.push_custom_cleanup_scope();
1500 bcx = insert_lllocals(bcx, &arm_data.bindings_map, Some(cleanup::CustomScope(cs)));
1501 bcx = expr::trans_into(bcx, &*arm_data.arm.body, dest);
1502 bcx = fcx.pop_and_trans_custom_cleanup_scope(bcx, cs);
1506 bcx = scope_cx.fcx.join_blocks(match_id, &arm_cxs[..]);
1510 /// Generates code for a local variable declaration like `let <pat>;` or `let <pat> =
1511 /// <opt_init_expr>`.
1512 pub fn store_local<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
1514 -> Block<'blk, 'tcx> {
1515 let _icx = push_ctxt("match::store_local");
1517 let tcx = bcx.tcx();
1518 let pat = &*local.pat;
1520 fn create_dummy_locals<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
1522 -> Block<'blk, 'tcx> {
1523 let _icx = push_ctxt("create_dummy_locals");
1524 // create dummy memory for the variables if we have no
1525 // value to store into them immediately
1526 let tcx = bcx.tcx();
1527 pat_bindings(&tcx.def_map, pat, |_, p_id, _, path1| {
1528 let scope = cleanup::var_scope(tcx, p_id);
1529 bcx = mk_binding_alloca(
1530 bcx, p_id, path1.node.name, scope, (),
1531 |(), bcx, llval, ty| { drop_done_fill_mem(bcx, llval, ty); bcx });
1537 Some(ref init_expr) => {
1538 // Optimize the "let x = expr" case. This just writes
1539 // the result of evaluating `expr` directly into the alloca
1540 // for `x`. Often the general path results in similar or the
1541 // same code post-optimization, but not always. In particular,
1542 // in unsafe code, you can have expressions like
1544 // let x = intrinsics::uninit();
1546 // In such cases, the more general path is unsafe, because
1547 // it assumes it is matching against a valid value.
1548 match simple_identifier(&*pat) {
1550 let var_scope = cleanup::var_scope(tcx, local.id);
1551 return mk_binding_alloca(
1552 bcx, pat.id, ident.name, var_scope, (),
1553 |(), bcx, v, _| expr::trans_into(bcx, &**init_expr,
1562 unpack_datum!(bcx, expr::trans_to_lvalue(bcx, &**init_expr, "let"));
1563 if bcx.sess().asm_comments() {
1564 add_comment(bcx, "creating zeroable ref llval");
1566 let var_scope = cleanup::var_scope(tcx, local.id);
1567 bind_irrefutable_pat(bcx, pat, init_datum.val, var_scope)
1570 create_dummy_locals(bcx, pat)
1575 /// Generates code for argument patterns like `fn foo(<pat>: T)`.
1576 /// Creates entries in the `lllocals` map for each of the bindings
1581 /// - `pat` is the argument pattern
1582 /// - `llval` is a pointer to the argument value (in other words,
1583 /// if the argument type is `T`, then `llval` is a `T*`). In some
1584 /// cases, this code may zero out the memory `llval` points at.
1585 pub fn store_arg<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
1587 arg: Datum<'tcx, Rvalue>,
1588 arg_scope: cleanup::ScopeId)
1589 -> Block<'blk, 'tcx> {
1590 let _icx = push_ctxt("match::store_arg");
1592 match simple_identifier(&*pat) {
1594 // Generate nicer LLVM for the common case of fn a pattern
1596 let arg_ty = node_id_type(bcx, pat.id);
1597 if type_of::arg_is_indirect(bcx.ccx(), arg_ty)
1598 && bcx.sess().opts.debuginfo != FullDebugInfo {
1599 // Don't copy an indirect argument to an alloca, the caller
1600 // already put it in a temporary alloca and gave it up, unless
1601 // we emit extra-debug-info, which requires local allocas :(.
1602 let arg_val = arg.add_clean(bcx.fcx, arg_scope);
1603 bcx.fcx.lllocals.borrow_mut()
1604 .insert(pat.id, Datum::new(arg_val, arg_ty, Lvalue));
1608 bcx, pat.id, ident.name, arg_scope, arg,
1609 |arg, bcx, llval, _| arg.store_to(bcx, llval))
1614 // General path. Copy out the values that are used in the
1616 let arg = unpack_datum!(
1617 bcx, arg.to_lvalue_datum_in_scope(bcx, "__arg", arg_scope));
1618 bind_irrefutable_pat(bcx, pat, arg.val, arg_scope)
1623 fn mk_binding_alloca<'blk, 'tcx, A, F>(bcx: Block<'blk, 'tcx>,
1626 cleanup_scope: cleanup::ScopeId,
1629 -> Block<'blk, 'tcx> where
1630 F: FnOnce(A, Block<'blk, 'tcx>, ValueRef, Ty<'tcx>) -> Block<'blk, 'tcx>,
1632 let var_ty = node_id_type(bcx, p_id);
1634 // Allocate memory on stack for the binding.
1635 let llval = alloc_ty(bcx, var_ty, &bcx.name(name));
1637 // Subtle: be sure that we *populate* the memory *before*
1638 // we schedule the cleanup.
1639 let bcx = populate(arg, bcx, llval, var_ty);
1640 bcx.fcx.schedule_lifetime_end(cleanup_scope, llval);
1641 bcx.fcx.schedule_drop_mem(cleanup_scope, llval, var_ty);
1643 // Now that memory is initialized and has cleanup scheduled,
1644 // create the datum and insert into the local variable map.
1645 let datum = Datum::new(llval, var_ty, Lvalue);
1646 bcx.fcx.lllocals.borrow_mut().insert(p_id, datum);
1650 /// A simple version of the pattern matching code that only handles
1651 /// irrefutable patterns. This is used in let/argument patterns,
1652 /// not in match statements. Unifying this code with the code above
1653 /// sounds nice, but in practice it produces very inefficient code,
1654 /// since the match code is so much more general. In most cases,
1655 /// LLVM is able to optimize the code, but it causes longer compile
1656 /// times and makes the generated code nigh impossible to read.
1659 /// - bcx: starting basic block context
1660 /// - pat: the irrefutable pattern being matched.
1661 /// - val: the value being matched -- must be an lvalue (by ref, with cleanup)
1662 fn bind_irrefutable_pat<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
1665 cleanup_scope: cleanup::ScopeId)
1666 -> Block<'blk, 'tcx> {
1667 debug!("bind_irrefutable_pat(bcx={}, pat={})",
1669 pat.repr(bcx.tcx()));
1671 if bcx.sess().asm_comments() {
1672 add_comment(bcx, &format!("bind_irrefutable_pat(pat={})",
1673 pat.repr(bcx.tcx())));
1676 let _indenter = indenter();
1678 let _icx = push_ctxt("match::bind_irrefutable_pat");
1680 let tcx = bcx.tcx();
1681 let ccx = bcx.ccx();
1683 ast::PatIdent(pat_binding_mode, ref path1, ref inner) => {
1684 if pat_is_binding(&tcx.def_map, &*pat) {
1685 // Allocate the stack slot where the value of this
1686 // binding will live and place it into the appropriate
1688 bcx = mk_binding_alloca(
1689 bcx, pat.id, path1.node.name, cleanup_scope, (),
1690 |(), bcx, llval, ty| {
1691 match pat_binding_mode {
1692 ast::BindByValue(_) => {
1693 // By value binding: move the value that `val`
1694 // points at into the binding's stack slot.
1695 let d = Datum::new(val, ty, Lvalue);
1696 d.store_to(bcx, llval)
1699 ast::BindByRef(_) => {
1700 // By ref binding: the value of the variable
1701 // is the pointer `val` itself or fat pointer referenced by `val`
1702 if type_is_fat_ptr(bcx.tcx(), ty) {
1703 expr::copy_fat_ptr(bcx, val, llval);
1706 Store(bcx, val, llval);
1715 if let Some(ref inner_pat) = *inner {
1716 bcx = bind_irrefutable_pat(bcx, &**inner_pat, val, cleanup_scope);
1719 ast::PatEnum(_, ref sub_pats) => {
1720 let opt_def = bcx.tcx().def_map.borrow().get(&pat.id).map(|d| d.full_def());
1722 Some(def::DefVariant(enum_id, var_id, _)) => {
1723 let repr = adt::represent_node(bcx, pat.id);
1724 let vinfo = ty::enum_variant_with_id(ccx.tcx(),
1727 let args = extract_variant_args(bcx,
1731 if let Some(ref sub_pat) = *sub_pats {
1732 for (i, &argval) in args.vals.iter().enumerate() {
1733 bcx = bind_irrefutable_pat(bcx, &*sub_pat[i],
1734 argval, cleanup_scope);
1738 Some(def::DefStruct(..)) => {
1741 // This is a unit-like struct. Nothing to do here.
1743 Some(ref elems) => {
1744 // This is the tuple struct case.
1745 let repr = adt::represent_node(bcx, pat.id);
1746 for (i, elem) in elems.iter().enumerate() {
1747 let fldptr = adt::trans_field_ptr(bcx, &*repr,
1749 bcx = bind_irrefutable_pat(bcx, &**elem,
1750 fldptr, cleanup_scope);
1756 // Nothing to do here.
1760 ast::PatStruct(_, ref fields, _) => {
1761 let tcx = bcx.tcx();
1762 let pat_ty = node_id_type(bcx, pat.id);
1763 let pat_repr = adt::represent_type(bcx.ccx(), pat_ty);
1764 expr::with_field_tys(tcx, pat_ty, Some(pat.id), |discr, field_tys| {
1766 let ix = ty::field_idx_strict(tcx, f.node.ident.name, field_tys);
1767 let fldptr = adt::trans_field_ptr(bcx, &*pat_repr, val,
1769 bcx = bind_irrefutable_pat(bcx, &*f.node.pat, fldptr, cleanup_scope);
1773 ast::PatTup(ref elems) => {
1774 let repr = adt::represent_node(bcx, pat.id);
1775 for (i, elem) in elems.iter().enumerate() {
1776 let fldptr = adt::trans_field_ptr(bcx, &*repr, val, 0, i);
1777 bcx = bind_irrefutable_pat(bcx, &**elem, fldptr, cleanup_scope);
1780 ast::PatBox(ref inner) => {
1781 let llbox = Load(bcx, val);
1782 bcx = bind_irrefutable_pat(bcx, &**inner, llbox, cleanup_scope);
1784 ast::PatRegion(ref inner, _) => {
1785 let loaded_val = Load(bcx, val);
1786 bcx = bind_irrefutable_pat(bcx, &**inner, loaded_val, cleanup_scope);
1788 ast::PatVec(ref before, ref slice, ref after) => {
1789 let pat_ty = node_id_type(bcx, pat.id);
1790 let mut extracted = extract_vec_elems(bcx, pat_ty, before.len(), after.len(), val);
1793 extracted.vals.insert(
1795 bind_subslice_pat(bcx, pat.id, val, before.len(), after.len())
1802 .chain(slice.iter())
1803 .chain(after.iter())
1804 .zip(extracted.vals.into_iter())
1805 .fold(bcx, |bcx, (inner, elem)|
1806 bind_irrefutable_pat(bcx, &**inner, elem, cleanup_scope)
1809 ast::PatMac(..) => {
1810 bcx.sess().span_bug(pat.span, "unexpanded macro");
1812 ast::PatQPath(..) | ast::PatWild(_) | ast::PatLit(_) |
1813 ast::PatRange(_, _) => ()