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.
14 use hair::{LintLevel, BindingMode, PatternKind};
16 use rustc::hir::def_id::{DefId, LocalDefId};
17 use rustc::middle::region;
19 use rustc::mir::visit::{MutVisitor, TyContext};
20 use rustc::ty::{self, Ty, TyCtxt};
21 use rustc::ty::subst::Substs;
22 use rustc::util::nodemap::NodeMap;
23 use rustc_target::spec::PanicStrategy;
24 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
28 use rustc_target::spec::abi::Abi;
30 use syntax::attr::{self, UnwindAttr};
31 use syntax::symbol::keywords;
33 use transform::MirSource;
36 /// Construct the MIR for a given def-id.
37 pub fn mir_build<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Mir<'tcx> {
38 let id = tcx.hir.as_local_node_id(def_id).unwrap();
39 let unsupported = || {
40 span_bug!(tcx.hir.span(id), "can't build MIR for {:?}", def_id);
43 // Figure out what primary body this item has.
44 let body_id = match tcx.hir.get(id) {
45 hir::map::NodeVariant(variant) =>
46 return create_constructor_shim(tcx, id, &variant.node.data),
47 hir::map::NodeStructCtor(ctor) =>
48 return create_constructor_shim(tcx, id, ctor),
50 _ => match tcx.hir.maybe_body_owned_by(id) {
52 None => unsupported(),
56 tcx.infer_ctxt().enter(|infcx| {
57 let cx = Cx::new(&infcx, id);
58 let mut mir = if cx.tables().tainted_by_errors {
59 build::construct_error(cx, body_id)
60 } else if let hir::BodyOwnerKind::Fn = cx.body_owner_kind {
61 // fetch the fully liberated fn signature (that is, all bound
62 // types/lifetimes replaced)
63 let fn_hir_id = tcx.hir.node_to_hir_id(id);
64 let fn_sig = cx.tables().liberated_fn_sigs()[fn_hir_id].clone();
66 let ty = tcx.type_of(tcx.hir.local_def_id(id));
67 let mut abi = fn_sig.abi;
68 let implicit_argument = match ty.sty {
69 ty::TyClosure(..) => {
70 // HACK(eddyb) Avoid having RustCall on closures,
71 // as it adds unnecessary (and wrong) auto-tupling.
73 Some(ArgInfo(liberated_closure_env_ty(tcx, id, body_id), None, None, None))
75 ty::TyGenerator(..) => {
76 let gen_ty = tcx.body_tables(body_id).node_id_to_type(fn_hir_id);
77 Some(ArgInfo(gen_ty, None, None, None))
82 // FIXME: safety in closures
83 let safety = match fn_sig.unsafety {
84 hir::Unsafety::Normal => Safety::Safe,
85 hir::Unsafety::Unsafe => Safety::FnUnsafe,
88 let body = tcx.hir.body(body_id);
89 let explicit_arguments =
94 let owner_id = tcx.hir.body_owner(body_id);
97 if let Some(ref fn_decl) = tcx.hir.fn_decl(owner_id) {
98 let ty_hir_id = fn_decl.inputs[index].hir_id;
99 let ty_span = tcx.hir.span(tcx.hir.hir_to_node_id(ty_hir_id));
100 opt_ty_info = Some(ty_span);
101 self_arg = if index == 0 && fn_decl.has_implicit_self {
102 Some(ImplicitSelfBinding)
110 ArgInfo(fn_sig.inputs()[index], opt_ty_info, Some(&*arg.pat), self_arg)
113 let arguments = implicit_argument.into_iter().chain(explicit_arguments);
115 let (yield_ty, return_ty) = if body.is_generator {
116 let gen_sig = match ty.sty {
117 ty::TyGenerator(gen_def_id, gen_substs, ..) =>
118 gen_substs.sig(gen_def_id, tcx),
120 span_bug!(tcx.hir.span(id), "generator w/o generator type: {:?}", ty),
122 (Some(gen_sig.yield_ty), gen_sig.return_ty)
124 (None, fn_sig.output())
127 build::construct_fn(cx, id, arguments, safety, abi,
128 return_ty, yield_ty, body)
130 build::construct_const(cx, body_id)
133 // Convert the Mir to global types.
134 let mut globalizer = GlobalizeMir {
138 globalizer.visit_mir(&mut mir);
140 mem::transmute::<Mir, Mir<'tcx>>(mir)
143 mir_util::dump_mir(tcx, None, "mir_map", &0,
144 MirSource::item(def_id), &mir, |_, _| Ok(()) );
150 /// A pass to lift all the types and substitutions in a Mir
151 /// to the global tcx. Sadly, we don't have a "folder" that
152 /// can change 'tcx so we have to transmute afterwards.
153 struct GlobalizeMir<'a, 'gcx: 'a> {
154 tcx: TyCtxt<'a, 'gcx, 'gcx>,
158 impl<'a, 'gcx: 'tcx, 'tcx> MutVisitor<'tcx> for GlobalizeMir<'a, 'gcx> {
159 fn visit_ty(&mut self, ty: &mut Ty<'tcx>, _: TyContext) {
160 if let Some(lifted) = self.tcx.lift(ty) {
164 "found type `{:?}` with inference types/regions in MIR",
169 fn visit_region(&mut self, region: &mut ty::Region<'tcx>, _: Location) {
170 if let Some(lifted) = self.tcx.lift(region) {
174 "found region `{:?}` with inference types/regions in MIR",
179 fn visit_const(&mut self, constant: &mut &'tcx ty::Const<'tcx>, _: Location) {
180 if let Some(lifted) = self.tcx.lift(constant) {
184 "found constant `{:?}` with inference types/regions in MIR",
189 fn visit_substs(&mut self, substs: &mut &'tcx Substs<'tcx>, _: Location) {
190 if let Some(lifted) = self.tcx.lift(substs) {
194 "found substs `{:?}` with inference types/regions in MIR",
200 fn create_constructor_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
201 ctor_id: ast::NodeId,
202 v: &'tcx hir::VariantData)
205 let span = tcx.hir.span(ctor_id);
206 if let hir::VariantData::Tuple(ref fields, ctor_id) = *v {
207 tcx.infer_ctxt().enter(|infcx| {
208 let mut mir = shim::build_adt_ctor(&infcx, ctor_id, fields, span);
210 // Convert the Mir to global types.
211 let tcx = infcx.tcx.global_tcx();
212 let mut globalizer = GlobalizeMir {
216 globalizer.visit_mir(&mut mir);
218 mem::transmute::<Mir, Mir<'tcx>>(mir)
221 mir_util::dump_mir(tcx, None, "mir_map", &0,
222 MirSource::item(tcx.hir.local_def_id(ctor_id)),
223 &mir, |_, _| Ok(()) );
228 span_bug!(span, "attempting to create MIR for non-tuple variant {:?}", v);
232 ///////////////////////////////////////////////////////////////////////////
233 // BuildMir -- walks a crate, looking for fn items and methods to build MIR from
235 fn liberated_closure_env_ty<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
236 closure_expr_id: ast::NodeId,
237 body_id: hir::BodyId)
239 let closure_expr_hir_id = tcx.hir.node_to_hir_id(closure_expr_id);
240 let closure_ty = tcx.body_tables(body_id).node_id_to_type(closure_expr_hir_id);
242 let (closure_def_id, closure_substs) = match closure_ty.sty {
243 ty::TyClosure(closure_def_id, closure_substs) => (closure_def_id, closure_substs),
244 _ => bug!("closure expr does not have closure type: {:?}", closure_ty)
247 let closure_env_ty = tcx.closure_env_ty(closure_def_id, closure_substs).unwrap();
248 tcx.liberate_late_bound_regions(closure_def_id, &closure_env_ty)
251 struct Builder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
252 hir: Cx<'a, 'gcx, 'tcx>,
258 /// the current set of scopes, updated as we traverse;
259 /// see the `scope` module for more details
260 scopes: Vec<scope::Scope<'tcx>>,
262 /// The current unsafe block in scope, even if it is hidden by
263 /// a PushUnsafeBlock
264 unpushed_unsafe: Safety,
266 /// The number of `push_unsafe_block` levels in scope
267 push_unsafe_count: usize,
269 /// the current set of breakables; see the `scope` module for more
271 breakable_scopes: Vec<scope::BreakableScope<'tcx>>,
273 /// the vector of all scopes that we have created thus far;
274 /// we track this for debuginfo later
275 source_scopes: IndexVec<SourceScope, SourceScopeData>,
276 source_scope_local_data: IndexVec<SourceScope, SourceScopeLocalData>,
277 source_scope: SourceScope,
279 /// the guard-context: each time we build the guard expression for
280 /// a match arm, we push onto this stack, and then pop when we
281 /// finish building it.
282 guard_context: Vec<GuardFrame>,
284 /// Maps node ids of variable bindings to the `Local`s created for them.
285 /// (A match binding can have two locals; the 2nd is for the arm's guard.)
286 var_indices: NodeMap<LocalsForNode>,
287 local_decls: IndexVec<Local, LocalDecl<'tcx>>,
288 unit_temp: Option<Place<'tcx>>,
290 /// cached block with the RESUME terminator; this is created
291 /// when first set of cleanups are built.
292 cached_resume_block: Option<BasicBlock>,
293 /// cached block with the RETURN terminator
294 cached_return_block: Option<BasicBlock>,
295 /// cached block with the UNREACHABLE terminator
296 cached_unreachable_block: Option<BasicBlock>,
299 impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
300 fn is_bound_var_in_guard(&self, id: ast::NodeId) -> bool {
301 self.guard_context.iter().any(|frame| frame.locals.iter().any(|local| local.id == id))
304 fn var_local_id(&self, id: ast::NodeId, for_guard: ForGuard) -> Local {
305 self.var_indices[&id].local_id(for_guard)
312 Three { val_for_guard: Local, ref_for_guard: Local, for_arm_body: Local },
316 struct GuardFrameLocal {
320 impl GuardFrameLocal {
321 fn new(id: ast::NodeId, _binding_mode: BindingMode) -> Self {
330 /// These are the id's of names that are bound by patterns of the
331 /// arm of *this* guard.
333 /// (Frames higher up the stack will have the id's bound in arms
334 /// further out, such as in a case like:
337 /// P1(id1) if (... (match E2 { P2(id2) if ... => B2 })) => B1,
340 /// here, when building for FIXME
341 locals: Vec<GuardFrameLocal>,
344 /// ForGuard indicates whether we are talking about:
345 /// 1. the temp for a local binding used solely within guard expressions,
346 /// 2. the temp that holds reference to (1.), which is actually what the
347 /// guard expressions see, or
348 /// 3. the temp for use outside of guard expressions.
349 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
357 fn local_id(&self, for_guard: ForGuard) -> Local {
358 match (self, for_guard) {
359 (&LocalsForNode::One(local_id), ForGuard::OutsideGuard) |
360 (&LocalsForNode::Three { val_for_guard: local_id, .. }, ForGuard::ValWithinGuard) |
361 (&LocalsForNode::Three { ref_for_guard: local_id, .. }, ForGuard::RefWithinGuard) |
362 (&LocalsForNode::Three { for_arm_body: local_id, .. }, ForGuard::OutsideGuard) =>
365 (&LocalsForNode::One(_), ForGuard::ValWithinGuard) |
366 (&LocalsForNode::One(_), ForGuard::RefWithinGuard) =>
367 bug!("anything with one local should never be within a guard."),
373 basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
376 newtype_index!(ScopeId);
378 ///////////////////////////////////////////////////////////////////////////
379 /// The `BlockAnd` "monad" packages up the new basic block along with a
380 /// produced value (sometimes just unit, of course). The `unpack!`
381 /// macro (and methods below) makes working with `BlockAnd` much more
384 #[must_use = "if you don't use one of these results, you're leaving a dangling edge"]
385 struct BlockAnd<T>(BasicBlock, T);
387 trait BlockAndExtension {
388 fn and<T>(self, v: T) -> BlockAnd<T>;
389 fn unit(self) -> BlockAnd<()>;
392 impl BlockAndExtension for BasicBlock {
393 fn and<T>(self, v: T) -> BlockAnd<T> {
397 fn unit(self) -> BlockAnd<()> {
402 /// Update a block pointer and return the value.
403 /// Use it like `let x = unpack!(block = self.foo(block, foo))`.
404 macro_rules! unpack {
405 ($x:ident = $c:expr) => {
407 let BlockAnd(b, v) = $c;
415 let BlockAnd(b, ()) = $c;
421 fn should_abort_on_panic<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
425 // Not callable from C, so we can safely unwind through these
426 if abi == Abi::Rust || abi == Abi::RustCall { return false; }
428 // We never unwind, so it's not relevant to stop an unwind
429 if tcx.sess.panic_strategy() != PanicStrategy::Unwind { return false; }
431 // We cannot add landing pads, so don't add one
432 if tcx.sess.no_landing_pads() { return false; }
434 // This is a special case: some functions have a C abi but are meant to
435 // unwind anyway. Don't stop them.
436 let attrs = &tcx.get_attrs(fn_def_id);
437 match attr::find_unwind_attr(Some(tcx.sess.diagnostic()), attrs) {
439 // FIXME(rust-lang/rust#48251) -- Had to disable
440 // abort-on-panic for backwards compatibility reasons.
444 Some(UnwindAttr::Allowed) => false,
445 Some(UnwindAttr::Aborts) => true,
449 ///////////////////////////////////////////////////////////////////////////
450 /// the main entry point for building MIR for a function
452 struct ImplicitSelfBinding;
454 struct ArgInfo<'gcx>(Ty<'gcx>,
456 Option<&'gcx hir::Pat>,
457 Option<ImplicitSelfBinding>);
459 fn construct_fn<'a, 'gcx, 'tcx, A>(hir: Cx<'a, 'gcx, 'tcx>,
465 yield_ty: Option<Ty<'gcx>>,
466 body: &'gcx hir::Body)
468 where A: Iterator<Item=ArgInfo<'gcx>>
470 let arguments: Vec<_> = arguments.collect();
473 let span = tcx.hir.span(fn_id);
474 let mut builder = Builder::new(hir.clone(),
480 let fn_def_id = tcx.hir.local_def_id(fn_id);
481 let call_site_scope = region::Scope::CallSite(body.value.hir_id.local_id);
482 let arg_scope = region::Scope::Arguments(body.value.hir_id.local_id);
483 let mut block = START_BLOCK;
484 let source_info = builder.source_info(span);
485 let call_site_s = (call_site_scope, source_info);
486 unpack!(block = builder.in_scope(call_site_s, LintLevel::Inherited, block, |builder| {
487 if should_abort_on_panic(tcx, fn_def_id, abi) {
488 builder.schedule_abort();
491 let arg_scope_s = (arg_scope, source_info);
492 unpack!(block = builder.in_scope(arg_scope_s, LintLevel::Inherited, block, |builder| {
493 builder.args_and_body(block, &arguments, arg_scope, &body.value)
495 // Attribute epilogue to function's closing brace
496 let fn_end = span.shrink_to_hi();
497 let source_info = builder.source_info(fn_end);
498 let return_block = builder.return_block();
499 builder.cfg.terminate(block, source_info,
500 TerminatorKind::Goto { target: return_block });
501 builder.cfg.terminate(return_block, source_info,
502 TerminatorKind::Return);
503 // Attribute any unreachable codepaths to the function's closing brace
504 if let Some(unreachable_block) = builder.cached_unreachable_block {
505 builder.cfg.terminate(unreachable_block, source_info,
506 TerminatorKind::Unreachable);
510 assert_eq!(block, builder.return_block());
512 let mut spread_arg = None;
513 if abi == Abi::RustCall {
514 // RustCall pseudo-ABI untuples the last argument.
515 spread_arg = Some(Local::new(arguments.len()));
517 let closure_expr_id = tcx.hir.local_def_id(fn_id);
518 info!("fn_id {:?} has attrs {:?}", closure_expr_id,
519 tcx.get_attrs(closure_expr_id));
521 // Gather the upvars of a closure, if any.
522 let upvar_decls: Vec<_> = tcx.with_freevars(fn_id, |freevars| {
523 freevars.iter().map(|fv| {
524 let var_id = fv.var_id();
525 let var_hir_id = tcx.hir.node_to_hir_id(var_id);
526 let closure_expr_id = tcx.hir.local_def_id(fn_id);
527 let capture = hir.tables().upvar_capture(ty::UpvarId {
529 closure_expr_id: LocalDefId::from_def_id(closure_expr_id),
531 let by_ref = match capture {
532 ty::UpvarCapture::ByValue => false,
533 ty::UpvarCapture::ByRef(..) => true
535 let mut decl = UpvarDecl {
536 debug_name: keywords::Invalid.name(),
538 mutability: Mutability::Not,
540 if let Some(hir::map::NodeBinding(pat)) = tcx.hir.find(var_id) {
541 if let hir::PatKind::Binding(_, _, ident, _) = pat.node {
542 decl.debug_name = ident.name;
544 let bm = *hir.tables.pat_binding_modes()
546 .expect("missing binding mode");
547 if bm == ty::BindByValue(hir::MutMutable) {
548 decl.mutability = Mutability::Mut;
550 decl.mutability = Mutability::Not;
558 let mut mir = builder.finish(upvar_decls, yield_ty);
559 mir.spread_arg = spread_arg;
563 fn construct_const<'a, 'gcx, 'tcx>(hir: Cx<'a, 'gcx, 'tcx>,
564 body_id: hir::BodyId)
567 let ast_expr = &tcx.hir.body(body_id).value;
568 let ty = hir.tables().expr_ty_adjusted(ast_expr);
569 let owner_id = tcx.hir.body_owner(body_id);
570 let span = tcx.hir.span(owner_id);
571 let mut builder = Builder::new(hir.clone(), span, 0, Safety::Safe, ty);
573 let mut block = START_BLOCK;
574 let expr = builder.hir.mirror(ast_expr);
575 unpack!(block = builder.into_expr(&Place::Local(RETURN_PLACE), block, expr));
577 let source_info = builder.source_info(span);
578 builder.cfg.terminate(block, source_info, TerminatorKind::Return);
580 // Constants can't `return` so a return block should not be created.
581 assert_eq!(builder.cached_return_block, None);
583 // Constants may be match expressions in which case an unreachable block may
584 // be created, so terminate it properly.
585 if let Some(unreachable_block) = builder.cached_unreachable_block {
586 builder.cfg.terminate(unreachable_block, source_info,
587 TerminatorKind::Unreachable);
590 builder.finish(vec![], None)
593 fn construct_error<'a, 'gcx, 'tcx>(hir: Cx<'a, 'gcx, 'tcx>,
594 body_id: hir::BodyId)
596 let owner_id = hir.tcx().hir.body_owner(body_id);
597 let span = hir.tcx().hir.span(owner_id);
598 let ty = hir.tcx().types.err;
599 let mut builder = Builder::new(hir, span, 0, Safety::Safe, ty);
600 let source_info = builder.source_info(span);
601 builder.cfg.terminate(START_BLOCK, source_info, TerminatorKind::Unreachable);
602 builder.finish(vec![], None)
605 impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
606 fn new(hir: Cx<'a, 'gcx, 'tcx>,
611 -> Builder<'a, 'gcx, 'tcx> {
612 let lint_level = LintLevel::Explicit(hir.root_lint_level);
613 let mut builder = Builder {
615 cfg: CFG { basic_blocks: IndexVec::new() },
619 source_scopes: IndexVec::new(),
620 source_scope: OUTERMOST_SOURCE_SCOPE,
621 source_scope_local_data: IndexVec::new(),
622 guard_context: vec![],
623 push_unsafe_count: 0,
624 unpushed_unsafe: safety,
625 breakable_scopes: vec![],
626 local_decls: IndexVec::from_elem_n(LocalDecl::new_return_place(return_ty,
628 var_indices: NodeMap(),
630 cached_resume_block: None,
631 cached_return_block: None,
632 cached_unreachable_block: None,
635 assert_eq!(builder.cfg.start_new_block(), START_BLOCK);
637 builder.new_source_scope(span, lint_level, Some(safety)),
638 OUTERMOST_SOURCE_SCOPE);
639 builder.source_scopes[OUTERMOST_SOURCE_SCOPE].parent_scope = None;
645 upvar_decls: Vec<UpvarDecl>,
646 yield_ty: Option<Ty<'tcx>>)
648 for (index, block) in self.cfg.basic_blocks.iter().enumerate() {
649 if block.terminator.is_none() {
650 span_bug!(self.fn_span, "no terminator on block {:?}", index);
654 Mir::new(self.cfg.basic_blocks,
656 ClearCrossCrate::Set(self.source_scope_local_data),
666 fn args_and_body(&mut self,
667 mut block: BasicBlock,
668 arguments: &[ArgInfo<'gcx>],
669 argument_scope: region::Scope,
670 ast_body: &'gcx hir::Expr)
673 // Allocate locals for the function arguments
674 for &ArgInfo(ty, _, pattern, _) in arguments.iter() {
675 // If this is a simple binding pattern, give the local a nice name for debuginfo.
677 if let Some(pat) = pattern {
678 if let hir::PatKind::Binding(_, _, ident, _) = pat.node {
679 name = Some(ident.name);
683 let source_info = SourceInfo {
684 scope: OUTERMOST_SOURCE_SCOPE,
685 span: pattern.map_or(self.fn_span, |pat| pat.span)
687 self.local_decls.push(LocalDecl {
688 mutability: Mutability::Mut,
691 visibility_scope: source_info.scope,
694 is_user_variable: None,
698 let mut scope = None;
699 // Bind the argument patterns
700 for (index, arg_info) in arguments.iter().enumerate() {
701 // Function arguments always get the first Local indices after the return place
702 let local = Local::new(index + 1);
703 let place = Place::Local(local);
704 let &ArgInfo(ty, opt_ty_info, pattern, ref self_binding) = arg_info;
706 if let Some(pattern) = pattern {
707 let pattern = self.hir.pattern_from_hir(pattern);
709 match *pattern.kind {
710 // Don't introduce extra copies for simple bindings
711 PatternKind::Binding { mutability, var, mode: BindingMode::ByValue, .. } => {
712 self.local_decls[local].mutability = mutability;
713 self.local_decls[local].is_user_variable =
714 if let Some(ImplicitSelfBinding) = self_binding {
715 Some(ClearCrossCrate::Set(BindingForm::ImplicitSelf))
717 let binding_mode = ty::BindingMode::BindByValue(mutability.into());
718 Some(ClearCrossCrate::Set(BindingForm::Var(VarBindingForm {
719 binding_mode, opt_ty_info })))
721 self.var_indices.insert(var, LocalsForNode::One(local));
724 scope = self.declare_bindings(scope, ast_body.span,
725 LintLevel::Inherited, &pattern,
726 matches::ArmHasGuard(false));
727 unpack!(block = self.place_into_pattern(block, pattern, &place));
732 // Make sure we drop (parts of) the argument even when not matched on.
733 self.schedule_drop(pattern.as_ref().map_or(ast_body.span, |pat| pat.span),
734 argument_scope, &place, ty);
738 // Enter the argument pattern bindings source scope, if it exists.
739 if let Some(source_scope) = scope {
740 self.source_scope = source_scope;
743 let body = self.hir.mirror(ast_body);
744 self.into(&Place::Local(RETURN_PLACE), block, body)
747 fn get_unit_temp(&mut self) -> Place<'tcx> {
748 match self.unit_temp {
749 Some(ref tmp) => tmp.clone(),
751 let ty = self.hir.unit_ty();
752 let fn_span = self.fn_span;
753 let tmp = self.temp(ty, fn_span);
754 self.unit_temp = Some(tmp.clone());
760 fn return_block(&mut self) -> BasicBlock {
761 match self.cached_return_block {
764 let rb = self.cfg.start_new_block();
765 self.cached_return_block = Some(rb);
771 fn unreachable_block(&mut self) -> BasicBlock {
772 match self.cached_unreachable_block {
775 let ub = self.cfg.start_new_block();
776 self.cached_unreachable_block = Some(ub);
783 ///////////////////////////////////////////////////////////////////////////
784 // Builder methods are broken up into modules, depending on what kind
785 // of thing is being lowered. Note that they use the `unpack` macro
786 // above extensively.