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 //! See the section on datums in `doc.rs` for an overview of what Datums are and how they are
12 //! intended to be used.
14 pub use self::Expr::*;
15 pub use self::RvalueMode::*;
19 use trans::build::Load;
22 use trans::cleanup::CleanupMethods;
26 use middle::ty::{mod, Ty};
27 use util::ppaux::{ty_to_string};
32 /// A `Datum` encapsulates the result of evaluating an expression. It
33 /// describes where the value is stored, what Rust type the value has,
34 /// whether it is addressed by reference, and so forth. Please refer
35 /// the section on datums in `doc.rs` for more details.
37 pub struct Datum<'tcx, K> {
38 /// The llvm value. This is either a pointer to the Rust value or
39 /// the value itself, depending on `kind` below.
42 /// The rust type of the value.
45 /// Indicates whether this is by-ref or by-value.
49 pub struct DatumBlock<'blk, 'tcx: 'blk, K> {
50 pub bcx: Block<'blk, 'tcx>,
51 pub datum: Datum<'tcx, K>,
56 /// a fresh value that was produced and which has no cleanup yet
57 /// because it has not yet "landed" into its permanent home
60 /// `val` is a pointer into memory for which a cleanup is scheduled
61 /// (and thus has type *T). If you move out of an Lvalue, you must
62 /// zero out the memory (FIXME #5016).
66 #[deriving(Clone, Show)]
75 pub fn new(m: RvalueMode) -> Rvalue {
80 // Make Datum linear for more type safety.
81 impl Drop for Rvalue {
82 fn drop(&mut self) { }
85 #[deriving(PartialEq, Eq, Hash, Show)]
87 /// `val` is a pointer to the actual value (and thus has type *T)
90 /// `val` is the actual value (*only used for immediates* like ints, ptrs)
94 pub fn immediate_rvalue<'tcx>(val: ValueRef, ty: Ty<'tcx>) -> Datum<'tcx, Rvalue> {
95 return Datum::new(val, ty, Rvalue::new(ByValue));
98 pub fn immediate_rvalue_bcx<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
101 -> DatumBlock<'blk, 'tcx, Rvalue> {
102 return DatumBlock::new(bcx, immediate_rvalue(val, ty))
106 /// Allocates temporary space on the stack using alloca() and returns a by-ref Datum pointing to
107 /// it. The memory will be dropped upon exit from `scope`. The callback `populate` should
108 /// initialize the memory. If `zero` is true, the space will be zeroed when it is allocated; this
109 /// is not necessary unless `bcx` does not dominate the end of `scope`.
110 pub fn lvalue_scratch_datum<'blk, 'tcx, A>(bcx: Block<'blk, 'tcx>,
114 scope: cleanup::ScopeId,
116 populate: |A, Block<'blk, 'tcx>, ValueRef|
117 -> Block<'blk, 'tcx>)
118 -> DatumBlock<'blk, 'tcx, Lvalue> {
119 let scratch = if zero {
120 alloca_zeroed(bcx, ty, name)
122 let llty = type_of::type_of(bcx.ccx(), ty);
123 alloca(bcx, llty, name)
126 // Subtle. Populate the scratch memory *before* scheduling cleanup.
127 let bcx = populate(arg, bcx, scratch);
128 bcx.fcx.schedule_lifetime_end(scope, scratch);
129 bcx.fcx.schedule_drop_mem(scope, scratch, ty);
131 DatumBlock::new(bcx, Datum::new(scratch, ty, Lvalue))
134 /// Allocates temporary space on the stack using alloca() and returns a by-ref Datum pointing to
135 /// it. If `zero` is true, the space will be zeroed when it is allocated; this is normally not
136 /// necessary, but in the case of automatic rooting in match statements it is possible to have
137 /// temporaries that may not get initialized if a certain arm is not taken, so we must zero them.
138 /// You must arrange any cleanups etc yourself!
139 pub fn rvalue_scratch_datum<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
142 -> Datum<'tcx, Rvalue> {
143 let llty = type_of::type_of(bcx.ccx(), ty);
144 let scratch = alloca(bcx, llty, name);
145 Datum::new(scratch, ty, Rvalue::new(ByRef))
148 /// Indicates the "appropriate" mode for this value, which is either by ref or by value, depending
149 /// on whether type is immediate or not.
150 pub fn appropriate_rvalue_mode<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
151 ty: Ty<'tcx>) -> RvalueMode {
152 if type_is_immediate(ccx, ty) {
159 fn add_rvalue_clean<'a, 'tcx>(mode: RvalueMode,
160 fcx: &FunctionContext<'a, 'tcx>,
161 scope: cleanup::ScopeId,
165 ByValue => { fcx.schedule_drop_immediate(scope, val, ty); }
167 fcx.schedule_lifetime_end(scope, val);
168 fcx.schedule_drop_mem(scope, val, ty);
175 /// Take appropriate action after the value in `datum` has been
176 /// stored to a new location.
177 fn post_store<'blk, 'tcx>(&self,
178 bcx: Block<'blk, 'tcx>,
181 -> Block<'blk, 'tcx>;
183 /// True if this mode is a reference mode, meaning that the datum's
184 /// val field is a pointer to the actual value
185 fn is_by_ref(&self) -> bool;
187 /// Converts to an Expr kind
188 fn to_expr_kind(self) -> Expr;
192 impl KindOps for Rvalue {
193 fn post_store<'blk, 'tcx>(&self,
194 bcx: Block<'blk, 'tcx>,
197 -> Block<'blk, 'tcx> {
198 // No cleanup is scheduled for an rvalue, so we don't have
199 // to do anything after a move to cancel or duplicate it.
203 fn is_by_ref(&self) -> bool {
207 fn to_expr_kind(self) -> Expr {
212 impl KindOps for Lvalue {
213 /// If an lvalue is moved, we must zero out the memory in which it resides so as to cancel
214 /// cleanup. If an @T lvalue is copied, we must increment the reference count.
215 fn post_store<'blk, 'tcx>(&self,
216 bcx: Block<'blk, 'tcx>,
219 -> Block<'blk, 'tcx> {
220 if ty::type_needs_drop(bcx.tcx(), ty) {
221 // cancel cleanup of affine values by zeroing out
222 let () = zero_mem(bcx, val, ty);
229 fn is_by_ref(&self) -> bool {
233 fn to_expr_kind(self) -> Expr {
238 impl KindOps for Expr {
239 fn post_store<'blk, 'tcx>(&self,
240 bcx: Block<'blk, 'tcx>,
243 -> Block<'blk, 'tcx> {
245 LvalueExpr => Lvalue.post_store(bcx, val, ty),
246 RvalueExpr(ref r) => r.post_store(bcx, val, ty),
250 fn is_by_ref(&self) -> bool {
252 LvalueExpr => Lvalue.is_by_ref(),
253 RvalueExpr(ref r) => r.is_by_ref()
257 fn to_expr_kind(self) -> Expr {
262 impl<'tcx> Datum<'tcx, Rvalue> {
263 /// Schedules a cleanup for this datum in the given scope. That means that this datum is no
264 /// longer an rvalue datum; hence, this function consumes the datum and returns the contained
266 pub fn add_clean<'a>(self,
267 fcx: &FunctionContext<'a, 'tcx>,
268 scope: cleanup::ScopeId)
270 add_rvalue_clean(self.kind.mode, fcx, scope, self.val, self.ty);
274 /// Returns an lvalue datum (that is, a by ref datum with cleanup scheduled). If `self` is not
275 /// already an lvalue, cleanup will be scheduled in the temporary scope for `expr_id`.
276 pub fn to_lvalue_datum_in_scope<'blk>(self,
277 bcx: Block<'blk, 'tcx>,
279 scope: cleanup::ScopeId)
280 -> DatumBlock<'blk, 'tcx, Lvalue> {
283 match self.kind.mode {
285 add_rvalue_clean(ByRef, fcx, scope, self.val, self.ty);
286 DatumBlock::new(bcx, Datum::new(self.val, self.ty, Lvalue))
290 lvalue_scratch_datum(
291 bcx, self.ty, name, false, scope, self,
292 |this, bcx, llval| this.store_to(bcx, llval))
297 pub fn to_ref_datum<'blk>(self, bcx: Block<'blk, 'tcx>)
298 -> DatumBlock<'blk, 'tcx, Rvalue> {
300 match self.kind.mode {
301 ByRef => DatumBlock::new(bcx, self),
303 let scratch = rvalue_scratch_datum(bcx, self.ty, "to_ref");
304 bcx = self.store_to(bcx, scratch.val);
305 DatumBlock::new(bcx, scratch)
310 pub fn to_appropriate_datum<'blk>(self, bcx: Block<'blk, 'tcx>)
311 -> DatumBlock<'blk, 'tcx, Rvalue> {
312 match self.appropriate_rvalue_mode(bcx.ccx()) {
314 self.to_ref_datum(bcx)
317 match self.kind.mode {
318 ByValue => DatumBlock::new(bcx, self),
320 let llval = load_ty(bcx, self.val, self.ty);
321 DatumBlock::new(bcx, Datum::new(llval, self.ty, Rvalue::new(ByValue)))
329 /// Methods suitable for "expr" datums that could be either lvalues or
330 /// rvalues. These include coercions into lvalues/rvalues but also a number
331 /// of more general operations. (Some of those operations could be moved to
332 /// the more general `impl<K> Datum<K>`, but it's convenient to have them
333 /// here since we can `match self.kind` rather than having to implement
334 /// generic methods in `KindOps`.)
335 impl<'tcx> Datum<'tcx, Expr> {
336 fn match_kind<R>(self,
337 if_lvalue: |Datum<'tcx, Lvalue>| -> R,
338 if_rvalue: |Datum<'tcx, Rvalue>| -> R)
340 let Datum { val, ty, kind } = self;
342 LvalueExpr => if_lvalue(Datum::new(val, ty, Lvalue)),
343 RvalueExpr(r) => if_rvalue(Datum::new(val, ty, r)),
347 /// Asserts that this datum *is* an lvalue and returns it.
348 #[allow(dead_code)] // potentially useful
349 pub fn assert_lvalue(self, bcx: Block) -> Datum<'tcx, Lvalue> {
352 |_| bcx.sess().bug("assert_lvalue given rvalue"))
355 pub fn store_to_dest<'blk>(self,
356 bcx: Block<'blk, 'tcx>,
358 expr_id: ast::NodeId)
359 -> Block<'blk, 'tcx> {
362 self.add_clean_if_rvalue(bcx, expr_id);
365 expr::SaveIn(addr) => {
366 self.store_to(bcx, addr)
371 /// Arranges cleanup for `self` if it is an rvalue. Use when you are done working with a value
372 /// that may need drop.
373 pub fn add_clean_if_rvalue<'blk>(self,
374 bcx: Block<'blk, 'tcx>,
375 expr_id: ast::NodeId) {
377 |_| { /* Nothing to do, cleanup already arranged */ },
379 let scope = cleanup::temporary_scope(bcx.tcx(), expr_id);
380 r.add_clean(bcx.fcx, scope);
384 /// Ensures that `self` will get cleaned up, if it is not an lvalue already.
385 pub fn clean<'blk>(self,
386 bcx: Block<'blk, 'tcx>,
388 expr_id: ast::NodeId)
389 -> Block<'blk, 'tcx> {
390 self.to_lvalue_datum(bcx, name, expr_id).bcx
393 pub fn to_lvalue_datum<'blk>(self,
394 bcx: Block<'blk, 'tcx>,
396 expr_id: ast::NodeId)
397 -> DatumBlock<'blk, 'tcx, Lvalue> {
398 debug!("to_lvalue_datum self: {}", self.to_string(bcx.ccx()));
400 assert!(ty::lltype_is_sized(bcx.tcx(), self.ty),
401 "Trying to convert unsized value to lval");
403 |l| DatumBlock::new(bcx, l),
405 let scope = cleanup::temporary_scope(bcx.tcx(), expr_id);
406 r.to_lvalue_datum_in_scope(bcx, name, scope)
410 /// Ensures that we have an rvalue datum (that is, a datum with no cleanup scheduled).
411 pub fn to_rvalue_datum<'blk>(self,
412 bcx: Block<'blk, 'tcx>,
414 -> DatumBlock<'blk, 'tcx, Rvalue> {
418 match l.appropriate_rvalue_mode(bcx.ccx()) {
420 let scratch = rvalue_scratch_datum(bcx, l.ty, name);
421 bcx = l.store_to(bcx, scratch.val);
422 DatumBlock::new(bcx, scratch)
425 let v = load_ty(bcx, l.val, l.ty);
426 bcx = l.kind.post_store(bcx, l.val, l.ty);
427 DatumBlock::new(bcx, Datum::new(v, l.ty, Rvalue::new(ByValue)))
431 |r| DatumBlock::new(bcx, r))
436 /// Methods suitable only for lvalues. These include the various
437 /// operations to extract components out of compound data structures,
438 /// such as extracting the field from a struct or a particular element
440 impl<'tcx> Datum<'tcx, Lvalue> {
441 /// Converts a datum into a by-ref value. The datum type must be one which is always passed by
443 pub fn to_llref(self) -> ValueRef {
447 // Extracts a component of a compound data structure (e.g., a field from a
448 // struct). Note that if self is an opened, unsized type then the returned
449 // datum may also be unsized _without the size information_. It is the
450 // callers responsibility to package the result in some way to make a valid
451 // datum in that case (e.g., by making a fat pointer or opened pair).
452 pub fn get_element<'blk>(&self, bcx: Block<'blk, 'tcx>, ty: Ty<'tcx>,
453 gep: |ValueRef| -> ValueRef)
454 -> Datum<'tcx, Lvalue> {
455 let val = match self.ty.sty {
456 _ if ty::type_is_sized(bcx.tcx(), self.ty) => gep(self.val),
458 let base = Load(bcx, expr::get_dataptr(bcx, self.val));
461 _ => bcx.tcx().sess.bug(
462 format!("Unexpected unsized type in get_element: {}",
463 bcx.ty_to_string(self.ty)).as_slice())
472 pub fn get_vec_base_and_len(&self, bcx: Block) -> (ValueRef, ValueRef) {
473 //! Converts a vector into the slice pair.
475 tvec::get_base_and_len(bcx, self.val, self.ty)
479 /// Generic methods applicable to any sort of datum.
480 impl<'tcx, K: KindOps + fmt::Show> Datum<'tcx, K> {
481 pub fn new(val: ValueRef, ty: Ty<'tcx>, kind: K) -> Datum<'tcx, K> {
482 Datum { val: val, ty: ty, kind: kind }
485 pub fn to_expr_datum(self) -> Datum<'tcx, Expr> {
486 let Datum { val, ty, kind } = self;
487 Datum { val: val, ty: ty, kind: kind.to_expr_kind() }
490 /// Moves or copies this value into a new home, as appropriate depending on the type of the
491 /// datum. This method consumes the datum, since it would be incorrect to go on using the datum
492 /// if the value represented is affine (and hence the value is moved).
493 pub fn store_to<'blk>(self,
494 bcx: Block<'blk, 'tcx>,
496 -> Block<'blk, 'tcx> {
497 self.shallow_copy_raw(bcx, dst);
499 self.kind.post_store(bcx, self.val, self.ty)
502 /// Helper function that performs a shallow copy of this value into `dst`, which should be a
503 /// pointer to a memory location suitable for `self.ty`. `dst` should contain uninitialized
504 /// memory (either newly allocated, zeroed, or dropped).
506 /// This function is private to datums because it leaves memory in an unstable state, where the
507 /// source value has been copied but not zeroed. Public methods are `store_to` (if you no
508 /// longer need the source value) or `shallow_copy` (if you wish the source value to remain
510 fn shallow_copy_raw<'blk>(&self,
511 bcx: Block<'blk, 'tcx>,
513 -> Block<'blk, 'tcx> {
514 let _icx = push_ctxt("copy_to_no_check");
516 if type_is_zero_size(bcx.ccx(), self.ty) {
520 if self.kind.is_by_ref() {
521 memcpy_ty(bcx, dst, self.val, self.ty);
523 store_ty(bcx, self.val, dst, self.ty);
529 /// Copies the value into a new location. This function always preserves the existing datum as
530 /// a valid value. Therefore, it does not consume `self` and, also, cannot be applied to affine
531 /// values (since they must never be duplicated).
532 pub fn shallow_copy<'blk>(&self,
533 bcx: Block<'blk, 'tcx>,
535 -> Block<'blk, 'tcx> {
536 assert!(!ty::type_moves_by_default(bcx.tcx(), self.ty));
537 self.shallow_copy_raw(bcx, dst)
540 #[allow(dead_code)] // useful for debugging
541 pub fn to_string<'a>(&self, ccx: &CrateContext<'a, 'tcx>) -> String {
542 format!("Datum({}, {}, {})",
543 ccx.tn().val_to_string(self.val),
544 ty_to_string(ccx.tcx(), self.ty),
548 /// See the `appropriate_rvalue_mode()` function
549 pub fn appropriate_rvalue_mode<'a>(&self, ccx: &CrateContext<'a, 'tcx>)
551 appropriate_rvalue_mode(ccx, self.ty)
554 /// Converts `self` into a by-value `ValueRef`. Consumes this datum (i.e., absolves you of
555 /// responsibility to cleanup the value). For this to work, the value must be something
556 /// scalar-ish (like an int or a pointer) which (1) does not require drop glue and (2) is
557 /// naturally passed around by value, and not by reference.
558 pub fn to_llscalarish<'blk>(self, bcx: Block<'blk, 'tcx>) -> ValueRef {
559 assert!(!ty::type_needs_drop(bcx.tcx(), self.ty));
560 assert!(self.appropriate_rvalue_mode(bcx.ccx()) == ByValue);
561 if self.kind.is_by_ref() {
562 load_ty(bcx, self.val, self.ty)
568 pub fn to_llbool<'blk>(self, bcx: Block<'blk, 'tcx>) -> ValueRef {
569 assert!(ty::type_is_bool(self.ty))
570 self.to_llscalarish(bcx)
574 impl<'blk, 'tcx, K> DatumBlock<'blk, 'tcx, K> {
575 pub fn new(bcx: Block<'blk, 'tcx>, datum: Datum<'tcx, K>)
576 -> DatumBlock<'blk, 'tcx, K> {
577 DatumBlock { bcx: bcx, datum: datum }
581 impl<'blk, 'tcx, K: KindOps + fmt::Show> DatumBlock<'blk, 'tcx, K> {
582 pub fn to_expr_datumblock(self) -> DatumBlock<'blk, 'tcx, Expr> {
583 DatumBlock::new(self.bcx, self.datum.to_expr_datum())
587 impl<'blk, 'tcx> DatumBlock<'blk, 'tcx, Expr> {
588 pub fn store_to_dest(self,
590 expr_id: ast::NodeId) -> Block<'blk, 'tcx> {
591 let DatumBlock { bcx, datum } = self;
592 datum.store_to_dest(bcx, dest, expr_id)
595 pub fn to_llbool(self) -> Result<'blk, 'tcx> {
596 let DatumBlock { datum, bcx } = self;
597 Result::new(bcx, datum.to_llbool(bcx))