1 // Copyright 2013 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 //! # Representation of Algebraic Data Types
13 //! This module determines how to represent enums, structs, and tuples
14 //! based on their monomorphized types; it is responsible both for
15 //! choosing a representation and translating basic operations on
16 //! values of those types. (Note: exporting the representations for
17 //! debuggers is handled in debuginfo.rs, not here.)
19 //! Note that the interface treats everything as a general case of an
20 //! enum, so structs/tuples/etc. have one pseudo-variant with
21 //! discriminant 0; i.e., as if they were a univariant enum.
23 //! Having everything in one place will enable improvements to data
24 //! structure representation; possibilities include:
26 //! - User-specified alignment (e.g., cacheline-aligning parts of
27 //! concurrently accessed data structures); LLVM can't represent this
28 //! directly, so we'd have to insert padding fields in any structure
29 //! that might contain one and adjust GEP indices accordingly. See
32 //! - Store nested enums' discriminants in the same word. Rather, if
33 //! some variants start with enums, and those enums representations
34 //! have unused alignment padding between discriminant and body, the
35 //! outer enum's discriminant can be stored there and those variants
36 //! can start at offset 0. Kind of fancy, and might need work to
37 //! make copies of the inner enum type cooperate, but it could help
38 //! with `Option` or `Result` wrapped around another enum.
40 //! - Tagged pointers would be neat, but given that any type can be
41 //! used unboxed and any field can have pointers (including mutable)
42 //! taken to it, implementing them for Rust seems difficult.
44 #![allow(unsigned_negation)]
46 pub use self::Repr
::*;
50 use llvm
::{ValueRef, True, IntEQ, IntNE}
;
51 use back
::abi
::FAT_PTR_ADDR
;
53 use middle
::ty
::{self, Ty, ClosureTyper}
;
57 use syntax
::attr
::IntType
;
61 use trans
::cleanup
::CleanupMethods
;
64 use trans
::debuginfo
::DebugLoc
;
66 use trans
::monomorphize
;
67 use trans
::type_
::Type
;
69 use util
::ppaux
::ty_to_string
;
71 type Hint
= attr
::ReprAttr
;
74 #[derive(Eq, PartialEq, Debug)]
76 /// C-like enums; basically an int.
77 CEnum(IntType
, Disr
, Disr
), // discriminant range (signedness based on the IntType)
78 /// Single-case variants, and structs/tuples/records.
80 /// Structs with destructors need a dynamic destroyedness flag to
81 /// avoid running the destructor too many times; this is included
82 /// in the `Struct` if present.
83 /// (The flag if nonzero, represents the initialization value to use;
84 /// if zero, then use no flag at all.)
85 Univariant(Struct
<'tcx
>, u8),
86 /// General-case enums: for each case there is a struct, and they
87 /// all start with a field for the discriminant.
89 /// Types with destructors need a dynamic destroyedness flag to
90 /// avoid running the destructor too many times; the last argument
91 /// indicates whether such a flag is present.
92 /// (The flag, if nonzero, represents the initialization value to use;
93 /// if zero, then use no flag at all.)
94 General(IntType
, Vec
<Struct
<'tcx
>>, u8),
95 /// Two cases distinguished by a nullable pointer: the case with discriminant
96 /// `nndiscr` must have single field which is known to be nonnull due to its type.
97 /// The other case is known to be zero sized. Hence we represent the enum
98 /// as simply a nullable pointer: if not null it indicates the `nndiscr` variant,
99 /// otherwise it indicates the other case.
103 nullfields
: Vec
<Ty
<'tcx
>>
105 /// Two cases distinguished by a nullable pointer: the case with discriminant
106 /// `nndiscr` is represented by the struct `nonnull`, where the `discrfield`th
107 /// field is known to be nonnull due to its type; if that field is null, then
108 /// it represents the other case, which is inhabited by at most one value
109 /// (and all other fields are undefined/unused).
111 /// For example, `std::option::Option` instantiated at a safe pointer type
112 /// is represented such that `None` is a null pointer and `Some` is the
113 /// identity function.
114 StructWrappedNullablePointer
{
115 nonnull
: Struct
<'tcx
>,
117 discrfield
: DiscrField
,
118 nullfields
: Vec
<Ty
<'tcx
>>,
122 /// For structs, and struct-like parts of anything fancier.
123 #[derive(Eq, PartialEq, Debug)]
124 pub struct Struct
<'tcx
> {
125 // If the struct is DST, then the size and alignment do not take into
126 // account the unsized fields of the struct.
131 pub fields
: Vec
<Ty
<'tcx
>>
134 /// Convenience for `represent_type`. There should probably be more or
135 /// these, for places in trans where the `Ty` isn't directly
137 pub fn represent_node
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>,
138 node
: ast
::NodeId
) -> Rc
<Repr
<'tcx
>> {
139 represent_type(bcx
.ccx(), node_id_type(bcx
, node
))
142 /// Decides how to represent a given type.
143 pub fn represent_type
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
146 debug
!("Representing: {}", ty_to_string(cx
.tcx(), t
));
147 match cx
.adt_reprs().borrow().get(&t
) {
148 Some(repr
) => return repr
.clone(),
152 let repr
= Rc
::new(represent_type_uncached(cx
, t
));
153 debug
!("Represented as: {:?}", repr
);
154 cx
.adt_reprs().borrow_mut().insert(t
, repr
.clone());
158 macro_rules
! repeat_u8_as_u32
{
159 ($name
:expr
) => { (($name
as u32) << 24 |
160 ($name
as u32) << 16 |
161 ($name
as u32) << 8 |
164 macro_rules
! repeat_u8_as_u64
{
165 ($name
:expr
) => { ((repeat_u8_as_u32
!($name
) as u64) << 32 |
166 (repeat_u8_as_u32
!($name
) as u64)) }
169 pub const DTOR_NEEDED
: u8 = 0xd4;
170 pub const DTOR_NEEDED_U32
: u32 = repeat_u8_as_u32
!(DTOR_NEEDED
);
171 pub const DTOR_NEEDED_U64
: u64 = repeat_u8_as_u64
!(DTOR_NEEDED
);
173 pub fn dtor_needed_usize(ccx
: &CrateContext
) -> usize {
174 match &ccx
.tcx().sess
.target
.target
.target_pointer_width
[..] {
175 "32" => DTOR_NEEDED_U32
as usize,
176 "64" => DTOR_NEEDED_U64
as usize,
177 tws
=> panic
!("Unsupported target word size for int: {}", tws
),
181 pub const DTOR_DONE
: u8 = 0x1d;
182 pub const DTOR_DONE_U32
: u32 = repeat_u8_as_u32
!(DTOR_DONE
);
183 pub const DTOR_DONE_U64
: u64 = repeat_u8_as_u64
!(DTOR_DONE
);
185 pub fn dtor_done_usize(ccx
: &CrateContext
) -> usize {
186 match &ccx
.tcx().sess
.target
.target
.target_pointer_width
[..] {
187 "32" => DTOR_DONE_U32
as usize,
188 "64" => DTOR_DONE_U64
as usize,
189 tws
=> panic
!("Unsupported target word size for int: {}", tws
),
193 fn dtor_to_init_u8(dtor
: bool
) -> u8 {
194 if dtor { DTOR_NEEDED }
else { 0 }
197 pub trait GetDtorType
<'tcx
> { fn dtor_type(&self) -> Ty<'tcx>; }
198 impl<'tcx
> GetDtorType
<'tcx
> for ty
::ctxt
<'tcx
> {
199 fn dtor_type(&self) -> Ty
<'tcx
> { self.types.u8 }
202 fn dtor_active(flag
: u8) -> bool
{
206 fn represent_type_uncached
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
207 t
: Ty
<'tcx
>) -> Repr
<'tcx
> {
209 ty
::ty_tup(ref elems
) => {
210 Univariant(mk_struct(cx
, &elems
[..], false, t
), 0)
212 ty
::ty_struct(def_id
, substs
) => {
213 let fields
= ty
::lookup_struct_fields(cx
.tcx(), def_id
);
214 let mut ftys
= fields
.iter().map(|field
| {
215 let fty
= ty
::lookup_field_type(cx
.tcx(), def_id
, field
.id
, substs
);
216 monomorphize
::normalize_associated_type(cx
.tcx(), &fty
)
217 }).collect
::<Vec
<_
>>();
218 let packed
= ty
::lookup_packed(cx
.tcx(), def_id
);
219 let dtor
= ty
::ty_dtor(cx
.tcx(), def_id
).has_drop_flag();
221 ftys
.push(cx
.tcx().dtor_type());
224 Univariant(mk_struct(cx
, &ftys
[..], packed
, t
), dtor_to_init_u8(dtor
))
226 ty
::ty_closure(def_id
, substs
) => {
227 let typer
= NormalizingClosureTyper
::new(cx
.tcx());
228 let upvars
= typer
.closure_upvars(def_id
, substs
).unwrap();
229 let upvar_types
= upvars
.iter().map(|u
| u
.ty
).collect
::<Vec
<_
>>();
230 Univariant(mk_struct(cx
, &upvar_types
[..], false, t
), 0)
232 ty
::ty_enum(def_id
, substs
) => {
233 let cases
= get_cases(cx
.tcx(), def_id
, substs
);
234 let hint
= *ty
::lookup_repr_hints(cx
.tcx(), def_id
).get(0)
235 .unwrap_or(&attr
::ReprAny
);
237 let dtor
= ty
::ty_dtor(cx
.tcx(), def_id
).has_drop_flag();
239 if cases
.is_empty() {
240 // Uninhabitable; represent as unit
241 // (Typechecking will reject discriminant-sizing attrs.)
242 assert_eq
!(hint
, attr
::ReprAny
);
243 let ftys
= if dtor { vec!(cx.tcx().dtor_type()) }
else { vec!() }
;
244 return Univariant(mk_struct(cx
, &ftys
[..], false, t
),
245 dtor_to_init_u8(dtor
));
248 if !dtor
&& cases
.iter().all(|c
| c
.tys
.is_empty()) {
249 // All bodies empty -> intlike
250 let discrs
: Vec
<u64> = cases
.iter().map(|c
| c
.discr
).collect();
251 let bounds
= IntBounds
{
252 ulo
: *discrs
.iter().min().unwrap(),
253 uhi
: *discrs
.iter().max().unwrap(),
254 slo
: discrs
.iter().map(|n
| *n
as i64).min().unwrap(),
255 shi
: discrs
.iter().map(|n
| *n
as i64).max().unwrap()
257 return mk_cenum(cx
, hint
, &bounds
);
260 // Since there's at least one
261 // non-empty body, explicit discriminants should have
262 // been rejected by a checker before this point.
263 if !cases
.iter().enumerate().all(|(i
,c
)| c
.discr
== (i
as Disr
)) {
264 cx
.sess().bug(&format
!("non-C-like enum {} with specified \
266 ty
::item_path_str(cx
.tcx(),
270 if cases
.len() == 1 {
271 // Equivalent to a struct/tuple/newtype.
272 // (Typechecking will reject discriminant-sizing attrs.)
273 assert_eq
!(hint
, attr
::ReprAny
);
274 let mut ftys
= cases
[0].tys
.clone();
275 if dtor { ftys.push(cx.tcx().dtor_type()); }
276 return Univariant(mk_struct(cx
, &ftys
[..], false, t
),
277 dtor_to_init_u8(dtor
));
280 if !dtor
&& cases
.len() == 2 && hint
== attr
::ReprAny
{
281 // Nullable pointer optimization
284 if cases
[1 - discr
].is_zerolen(cx
, t
) {
285 let st
= mk_struct(cx
, &cases
[discr
].tys
,
287 match cases
[discr
].find_ptr(cx
) {
288 Some(ref df
) if df
.len() == 1 && st
.fields
.len() == 1 => {
289 return RawNullablePointer
{
290 nndiscr
: discr
as Disr
,
292 nullfields
: cases
[1 - discr
].tys
.clone()
295 Some(mut discrfield
) => {
297 discrfield
.reverse();
298 return StructWrappedNullablePointer
{
299 nndiscr
: discr
as Disr
,
301 discrfield
: discrfield
,
302 nullfields
: cases
[1 - discr
].tys
.clone()
313 assert
!((cases
.len() - 1) as i64 >= 0);
314 let bounds
= IntBounds
{ ulo
: 0, uhi
: (cases
.len() - 1) as u64,
315 slo
: 0, shi
: (cases
.len() - 1) as i64 };
316 let min_ity
= range_to_inttype(cx
, hint
, &bounds
);
318 // Create the set of structs that represent each variant
319 // Use the minimum integer type we figured out above
320 let fields
: Vec
<_
> = cases
.iter().map(|c
| {
321 let mut ftys
= vec
!(ty_of_inttype(cx
.tcx(), min_ity
));
322 ftys
.push_all(&c
.tys
);
323 if dtor { ftys.push(cx.tcx().dtor_type()); }
324 mk_struct(cx
, &ftys
, false, t
)
328 // Check to see if we should use a different type for the
329 // discriminant. If the overall alignment of the type is
330 // the same as the first field in each variant, we can safely use
331 // an alignment-sized type.
332 // We increase the size of the discriminant to avoid LLVM copying
333 // padding when it doesn't need to. This normally causes unaligned
334 // load/stores and excessive memcpy/memset operations. By using a
335 // bigger integer size, LLVM can be sure about it's contents and
336 // won't be so conservative.
337 // This check is needed to avoid increasing the size of types when
338 // the alignment of the first field is smaller than the overall
339 // alignment of the type.
340 let (_
, align
) = union_size_and_align(&fields
);
341 let mut use_align
= true;
343 // Get the first non-zero-sized field
344 let field
= st
.fields
.iter().skip(1).filter(|ty
| {
345 let t
= type_of
::sizing_type_of(cx
, **ty
);
346 machine
::llsize_of_real(cx
, t
) != 0 ||
347 // This case is only relevant for zero-sized types with large alignment
348 machine
::llalign_of_min(cx
, t
) != 1
351 if let Some(field
) = field
{
352 let field_align
= type_of
::align_of(cx
, *field
);
353 if field_align
!= align
{
359 let ity
= if use_align
{
360 // Use the overall alignment
362 1 => attr
::UnsignedInt(ast
::TyU8
),
363 2 => attr
::UnsignedInt(ast
::TyU16
),
364 4 => attr
::UnsignedInt(ast
::TyU32
),
365 8 if machine
::llalign_of_min(cx
, Type
::i64(cx
)) == 8 =>
366 attr
::UnsignedInt(ast
::TyU64
),
367 _
=> min_ity
// use min_ity as a fallback
373 let fields
: Vec
<_
> = cases
.iter().map(|c
| {
374 let mut ftys
= vec
!(ty_of_inttype(cx
.tcx(), ity
));
375 ftys
.push_all(&c
.tys
);
376 if dtor { ftys.push(cx.tcx().dtor_type()); }
377 mk_struct(cx
, &ftys
[..], false, t
)
380 ensure_enum_fits_in_address_space(cx
, &fields
[..], t
);
382 General(ity
, fields
, dtor_to_init_u8(dtor
))
384 _
=> cx
.sess().bug(&format
!("adt::represent_type called on non-ADT type: {}",
385 ty_to_string(cx
.tcx(), t
)))
389 // this should probably all be in ty
395 /// This represents the (GEP) indices to follow to get to the discriminant field
396 pub type DiscrField
= Vec
<usize>;
398 fn find_discr_field_candidate
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>,
400 mut path
: DiscrField
) -> Option
<DiscrField
> {
402 // Fat &T/&mut T/Box<T> i.e. T is [T], str, or Trait
403 ty
::ty_rptr(_
, ty
::mt { ty, .. }
) | ty
::ty_uniq(ty
) if !type_is_sized(tcx
, ty
) => {
404 path
.push(FAT_PTR_ADDR
);
408 // Regular thin pointer: &T/&mut T/Box<T>
409 ty
::ty_rptr(..) | ty
::ty_uniq(..) => Some(path
),
411 // Functions are just pointers
412 ty
::ty_bare_fn(..) => Some(path
),
414 // Is this the NonZero lang item wrapping a pointer or integer type?
415 ty
::ty_struct(did
, substs
) if Some(did
) == tcx
.lang_items
.non_zero() => {
416 let nonzero_fields
= ty
::lookup_struct_fields(tcx
, did
);
417 assert_eq
!(nonzero_fields
.len(), 1);
418 let nonzero_field
= ty
::lookup_field_type(tcx
, did
, nonzero_fields
[0].id
, substs
);
419 match nonzero_field
.sty
{
420 ty
::ty_ptr(ty
::mt { ty, .. }
) if !type_is_sized(tcx
, ty
) => {
421 path
.push_all(&[0, FAT_PTR_ADDR
]);
424 ty
::ty_ptr(..) | ty
::ty_int(..) | ty
::ty_uint(..) => {
432 // Perhaps one of the fields of this struct is non-zero
433 // let's recurse and find out
434 ty
::ty_struct(def_id
, substs
) => {
435 let fields
= ty
::lookup_struct_fields(tcx
, def_id
);
436 for (j
, field
) in fields
.iter().enumerate() {
437 let field_ty
= ty
::lookup_field_type(tcx
, def_id
, field
.id
, substs
);
438 if let Some(mut fpath
) = find_discr_field_candidate(tcx
, field_ty
, path
.clone()) {
446 // Perhaps one of the upvars of this struct is non-zero
447 // Let's recurse and find out!
448 ty
::ty_closure(def_id
, substs
) => {
449 let typer
= NormalizingClosureTyper
::new(tcx
);
450 let upvars
= typer
.closure_upvars(def_id
, substs
).unwrap();
451 let upvar_types
= upvars
.iter().map(|u
| u
.ty
).collect
::<Vec
<_
>>();
453 for (j
, &ty
) in upvar_types
.iter().enumerate() {
454 if let Some(mut fpath
) = find_discr_field_candidate(tcx
, ty
, path
.clone()) {
462 // Can we use one of the fields in this tuple?
463 ty
::ty_tup(ref tys
) => {
464 for (j
, &ty
) in tys
.iter().enumerate() {
465 if let Some(mut fpath
) = find_discr_field_candidate(tcx
, ty
, path
.clone()) {
473 // Is this a fixed-size array of something non-zero
474 // with at least one element?
475 ty
::ty_vec(ety
, Some(d
)) if d
> 0 => {
476 if let Some(mut vpath
) = find_discr_field_candidate(tcx
, ety
, path
) {
484 // Anything else is not a pointer
489 impl<'tcx
> Case
<'tcx
> {
490 fn is_zerolen
<'a
>(&self, cx
: &CrateContext
<'a
, 'tcx
>, scapegoat
: Ty
<'tcx
>) -> bool
{
491 mk_struct(cx
, &self.tys
, false, scapegoat
).size
== 0
494 fn find_ptr
<'a
>(&self, cx
: &CrateContext
<'a
, 'tcx
>) -> Option
<DiscrField
> {
495 for (i
, &ty
) in self.tys
.iter().enumerate() {
496 if let Some(mut path
) = find_discr_field_candidate(cx
.tcx(), ty
, vec
![]) {
505 fn get_cases
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>,
507 substs
: &subst
::Substs
<'tcx
>)
509 ty
::enum_variants(tcx
, def_id
).iter().map(|vi
| {
510 let arg_tys
= vi
.args
.iter().map(|&raw_ty
| {
511 monomorphize
::apply_param_substs(tcx
, substs
, &raw_ty
)
513 Case { discr: vi.disr_val, tys: arg_tys }
517 fn mk_struct
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
518 tys
: &[Ty
<'tcx
>], packed
: bool
,
521 let sized
= tys
.iter().all(|&ty
| type_is_sized(cx
.tcx(), ty
));
522 let lltys
: Vec
<Type
> = if sized
{
523 tys
.iter().map(|&ty
| type_of
::sizing_type_of(cx
, ty
)).collect()
525 tys
.iter().filter(|&ty
| type_is_sized(cx
.tcx(), *ty
))
526 .map(|&ty
| type_of
::sizing_type_of(cx
, ty
)).collect()
529 ensure_struct_fits_in_address_space(cx
, &lltys
[..], packed
, scapegoat
);
531 let llty_rec
= Type
::struct_(cx
, &lltys
[..], packed
);
533 size
: machine
::llsize_of_alloc(cx
, llty_rec
),
534 align
: machine
::llalign_of_min(cx
, llty_rec
),
537 fields
: tys
.to_vec(),
549 fn mk_cenum
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
550 hint
: Hint
, bounds
: &IntBounds
)
552 let it
= range_to_inttype(cx
, hint
, bounds
);
554 attr
::SignedInt(_
) => CEnum(it
, bounds
.slo
as Disr
, bounds
.shi
as Disr
),
555 attr
::UnsignedInt(_
) => CEnum(it
, bounds
.ulo
, bounds
.uhi
)
559 fn range_to_inttype(cx
: &CrateContext
, hint
: Hint
, bounds
: &IntBounds
) -> IntType
{
560 debug
!("range_to_inttype: {:?} {:?}", hint
, bounds
);
561 // Lists of sizes to try. u64 is always allowed as a fallback.
562 #[allow(non_upper_case_globals)]
563 const choose_shortest
: &'
static [IntType
] = &[
564 attr
::UnsignedInt(ast
::TyU8
), attr
::SignedInt(ast
::TyI8
),
565 attr
::UnsignedInt(ast
::TyU16
), attr
::SignedInt(ast
::TyI16
),
566 attr
::UnsignedInt(ast
::TyU32
), attr
::SignedInt(ast
::TyI32
)];
567 #[allow(non_upper_case_globals)]
568 const at_least_32
: &'
static [IntType
] = &[
569 attr
::UnsignedInt(ast
::TyU32
), attr
::SignedInt(ast
::TyI32
)];
573 attr
::ReprInt(span
, ity
) => {
574 if !bounds_usable(cx
, ity
, bounds
) {
575 cx
.sess().span_bug(span
, "representation hint insufficient for discriminant range")
579 attr
::ReprExtern
=> {
580 attempts
= match &cx
.sess().target
.target
.arch
[..] {
581 // WARNING: the ARM EABI has two variants; the one corresponding to `at_least_32`
582 // appears to be used on Linux and NetBSD, but some systems may use the variant
583 // corresponding to `choose_shortest`. However, we don't run on those yet...?
584 "arm" => at_least_32
,
589 attempts
= choose_shortest
;
591 attr
::ReprPacked
=> {
592 cx
.tcx().sess
.bug("range_to_inttype: found ReprPacked on an enum");
595 for &ity
in attempts
{
596 if bounds_usable(cx
, ity
, bounds
) {
600 return attr
::UnsignedInt(ast
::TyU64
);
603 pub fn ll_inttype(cx
: &CrateContext
, ity
: IntType
) -> Type
{
605 attr
::SignedInt(t
) => Type
::int_from_ty(cx
, t
),
606 attr
::UnsignedInt(t
) => Type
::uint_from_ty(cx
, t
)
610 fn bounds_usable(cx
: &CrateContext
, ity
: IntType
, bounds
: &IntBounds
) -> bool
{
611 debug
!("bounds_usable: {:?} {:?}", ity
, bounds
);
613 attr
::SignedInt(_
) => {
614 let lllo
= C_integral(ll_inttype(cx
, ity
), bounds
.slo
as u64, true);
615 let llhi
= C_integral(ll_inttype(cx
, ity
), bounds
.shi
as u64, true);
616 bounds
.slo
== const_to_int(lllo
) as i64 && bounds
.shi
== const_to_int(llhi
) as i64
618 attr
::UnsignedInt(_
) => {
619 let lllo
= C_integral(ll_inttype(cx
, ity
), bounds
.ulo
, false);
620 let llhi
= C_integral(ll_inttype(cx
, ity
), bounds
.uhi
, false);
621 bounds
.ulo
== const_to_uint(lllo
) as u64 && bounds
.uhi
== const_to_uint(llhi
) as u64
626 pub fn ty_of_inttype
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>, ity
: IntType
) -> Ty
<'tcx
> {
628 attr
::SignedInt(t
) => ty
::mk_mach_int(tcx
, t
),
629 attr
::UnsignedInt(t
) => ty
::mk_mach_uint(tcx
, t
)
633 // LLVM doesn't like types that don't fit in the address space
634 fn ensure_struct_fits_in_address_space
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>,
637 scapegoat
: Ty
<'tcx
>) {
639 for &llty
in fields
{
640 // Invariant: offset < ccx.obj_size_bound() <= 1<<61
642 let type_align
= machine
::llalign_of_min(ccx
, llty
);
643 offset
= roundup(offset
, type_align
);
645 // type_align is a power-of-2, so still offset < ccx.obj_size_bound()
646 // llsize_of_alloc(ccx, llty) is also less than ccx.obj_size_bound()
647 // so the sum is less than 1<<62 (and therefore can't overflow).
648 offset
+= machine
::llsize_of_alloc(ccx
, llty
);
650 if offset
>= ccx
.obj_size_bound() {
651 ccx
.report_overbig_object(scapegoat
);
656 fn union_size_and_align(sts
: &[Struct
]) -> (machine
::llsize
, machine
::llalign
) {
657 let size
= sts
.iter().map(|st
| st
.size
).max().unwrap();
658 let align
= sts
.iter().map(|st
| st
.align
).max().unwrap();
659 (roundup(size
, align
), align
)
662 fn ensure_enum_fits_in_address_space
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>,
664 scapegoat
: Ty
<'tcx
>) {
665 let (total_size
, _
) = union_size_and_align(fields
);
667 if total_size
>= ccx
.obj_size_bound() {
668 ccx
.report_overbig_object(scapegoat
);
673 /// LLVM-level types are a little complicated.
675 /// C-like enums need to be actual ints, not wrapped in a struct,
676 /// because that changes the ABI on some platforms (see issue #10308).
678 /// For nominal types, in some cases, we need to use LLVM named structs
679 /// and fill in the actual contents in a second pass to prevent
680 /// unbounded recursion; see also the comments in `trans::type_of`.
681 pub fn type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>, r
: &Repr
<'tcx
>) -> Type
{
682 generic_type_of(cx
, r
, None
, false, false)
684 // Pass dst=true if the type you are passing is a DST. Yes, we could figure
685 // this out, but if you call this on an unsized type without realising it, you
686 // are going to get the wrong type (it will not include the unsized parts of it).
687 pub fn sizing_type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
688 r
: &Repr
<'tcx
>, dst
: bool
) -> Type
{
689 generic_type_of(cx
, r
, None
, true, dst
)
691 pub fn incomplete_type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
692 r
: &Repr
<'tcx
>, name
: &str) -> Type
{
693 generic_type_of(cx
, r
, Some(name
), false, false)
695 pub fn finish_type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
696 r
: &Repr
<'tcx
>, llty
: &mut Type
) {
698 CEnum(..) | General(..) | RawNullablePointer { .. }
=> { }
699 Univariant(ref st
, _
) | StructWrappedNullablePointer { nonnull: ref st, .. }
=>
700 llty
.set_struct_body(&struct_llfields(cx
, st
, false, false),
705 fn generic_type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
711 CEnum(ity
, _
, _
) => ll_inttype(cx
, ity
),
712 RawNullablePointer { nnty, .. }
=> type_of
::sizing_type_of(cx
, nnty
),
713 Univariant(ref st
, _
) | StructWrappedNullablePointer { nonnull: ref st, .. }
=> {
716 Type
::struct_(cx
, &struct_llfields(cx
, st
, sizing
, dst
),
719 Some(name
) => { assert_eq!(sizing, false); Type::named_struct(cx, name) }
722 General(ity
, ref sts
, _
) => {
723 // We need a representation that has:
724 // * The alignment of the most-aligned field
725 // * The size of the largest variant (rounded up to that alignment)
726 // * No alignment padding anywhere any variant has actual data
727 // (currently matters only for enums small enough to be immediate)
728 // * The discriminant in an obvious place.
730 // So we start with the discriminant, pad it up to the alignment with
731 // more of its own type, then use alignment-sized ints to get the rest
734 // FIXME #10604: this breaks when vector types are present.
735 let (size
, align
) = union_size_and_align(&sts
[..]);
736 let align_s
= align
as u64;
737 assert_eq
!(size
% align_s
, 0);
738 let align_units
= size
/ align_s
- 1;
740 let discr_ty
= ll_inttype(cx
, ity
);
741 let discr_size
= machine
::llsize_of_alloc(cx
, discr_ty
);
742 let fill_ty
= match align_s
{
743 1 => Type
::array(&Type
::i8(cx
), align_units
),
744 2 => Type
::array(&Type
::i16(cx
), align_units
),
745 4 => Type
::array(&Type
::i32(cx
), align_units
),
746 8 if machine
::llalign_of_min(cx
, Type
::i64(cx
)) == 8 =>
747 Type
::array(&Type
::i64(cx
), align_units
),
748 a
if a
.count_ones() == 1 => Type
::array(&Type
::vector(&Type
::i32(cx
), a
/ 4),
750 _
=> panic
!("unsupported enum alignment: {}", align
)
752 assert_eq
!(machine
::llalign_of_min(cx
, fill_ty
), align
);
753 assert_eq
!(align_s
% discr_size
, 0);
754 let fields
= [discr_ty
,
755 Type
::array(&discr_ty
, align_s
/ discr_size
- 1),
758 None
=> Type
::struct_(cx
, &fields
[..], false),
760 let mut llty
= Type
::named_struct(cx
, name
);
761 llty
.set_struct_body(&fields
[..], false);
769 fn struct_llfields
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>, st
: &Struct
<'tcx
>,
770 sizing
: bool
, dst
: bool
) -> Vec
<Type
> {
772 st
.fields
.iter().filter(|&ty
| !dst
|| type_is_sized(cx
.tcx(), *ty
))
773 .map(|&ty
| type_of
::sizing_type_of(cx
, ty
)).collect()
775 st
.fields
.iter().map(|&ty
| type_of
::in_memory_type_of(cx
, ty
)).collect()
779 /// Obtain a representation of the discriminant sufficient to translate
780 /// destructuring; this may or may not involve the actual discriminant.
782 /// This should ideally be less tightly tied to `_match`.
783 pub fn trans_switch
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>,
784 r
: &Repr
<'tcx
>, scrutinee
: ValueRef
)
785 -> (_match
::BranchKind
, Option
<ValueRef
>) {
787 CEnum(..) | General(..) |
788 RawNullablePointer { .. }
| StructWrappedNullablePointer { .. }
=> {
789 (_match
::Switch
, Some(trans_get_discr(bcx
, r
, scrutinee
, None
)))
792 // N.B.: Univariant means <= 1 enum variants (*not* == 1 variants).
793 (_match
::Single
, None
)
800 /// Obtain the actual discriminant of a value.
801 pub fn trans_get_discr
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
<'tcx
>,
802 scrutinee
: ValueRef
, cast_to
: Option
<Type
>)
806 debug
!("trans_get_discr r: {:?}", r
);
808 CEnum(ity
, min
, max
) => {
809 val
= load_discr(bcx
, ity
, scrutinee
, min
, max
);
810 signed
= ity
.is_signed();
812 General(ity
, ref cases
, _
) => {
813 let ptr
= GEPi(bcx
, scrutinee
, &[0, 0]);
814 val
= load_discr(bcx
, ity
, ptr
, 0, (cases
.len() - 1) as Disr
);
815 signed
= ity
.is_signed();
818 val
= C_u8(bcx
.ccx(), 0);
821 RawNullablePointer { nndiscr, nnty, .. }
=> {
822 let cmp
= if nndiscr
== 0 { IntEQ }
else { IntNE }
;
823 let llptrty
= type_of
::sizing_type_of(bcx
.ccx(), nnty
);
824 val
= ICmp(bcx
, cmp
, Load(bcx
, scrutinee
), C_null(llptrty
), DebugLoc
::None
);
827 StructWrappedNullablePointer { nndiscr, ref discrfield, .. }
=> {
828 val
= struct_wrapped_nullable_bitdiscr(bcx
, nndiscr
, discrfield
, scrutinee
);
834 Some(llty
) => if signed { SExt(bcx, val, llty) }
else { ZExt(bcx, val, llty) }
838 fn struct_wrapped_nullable_bitdiscr(bcx
: Block
, nndiscr
: Disr
, discrfield
: &DiscrField
,
839 scrutinee
: ValueRef
) -> ValueRef
{
840 let llptrptr
= GEPi(bcx
, scrutinee
, &discrfield
[..]);
841 let llptr
= Load(bcx
, llptrptr
);
842 let cmp
= if nndiscr
== 0 { IntEQ }
else { IntNE }
;
843 ICmp(bcx
, cmp
, llptr
, C_null(val_ty(llptr
)), DebugLoc
::None
)
846 /// Helper for cases where the discriminant is simply loaded.
847 fn load_discr(bcx
: Block
, ity
: IntType
, ptr
: ValueRef
, min
: Disr
, max
: Disr
)
849 let llty
= ll_inttype(bcx
.ccx(), ity
);
850 assert_eq
!(val_ty(ptr
), llty
.ptr_to());
851 let bits
= machine
::llbitsize_of_real(bcx
.ccx(), llty
);
853 let bits
= bits
as usize;
854 let mask
= (!0u64 >> (64 - bits
)) as Disr
;
855 // For a (max) discr of -1, max will be `-1 as usize`, which overflows.
856 // However, that is fine here (it would still represent the full range),
857 if (max
.wrapping_add(1)) & mask
== min
& mask
{
858 // i.e., if the range is everything. The lo==hi case would be
859 // rejected by the LLVM verifier (it would mean either an
860 // empty set, which is impossible, or the entire range of the
861 // type, which is pointless).
864 // llvm::ConstantRange can deal with ranges that wrap around,
865 // so an overflow on (max + 1) is fine.
866 LoadRangeAssert(bcx
, ptr
, min
, (max
.wrapping_add(1)), /* signed: */ True
)
870 /// Yield information about how to dispatch a case of the
871 /// discriminant-like value returned by `trans_switch`.
873 /// This should ideally be less tightly tied to `_match`.
874 pub fn trans_case
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
, discr
: Disr
)
875 -> _match
::OptResult
<'blk
, 'tcx
> {
877 CEnum(ity
, _
, _
) => {
878 _match
::SingleResult(Result
::new(bcx
, C_integral(ll_inttype(bcx
.ccx(), ity
),
879 discr
as u64, true)))
881 General(ity
, _
, _
) => {
882 _match
::SingleResult(Result
::new(bcx
, C_integral(ll_inttype(bcx
.ccx(), ity
),
883 discr
as u64, true)))
886 bcx
.ccx().sess().bug("no cases for univariants or structs")
888 RawNullablePointer { .. }
|
889 StructWrappedNullablePointer { .. }
=> {
890 assert
!(discr
== 0 || discr
== 1);
891 _match
::SingleResult(Result
::new(bcx
, C_bool(bcx
.ccx(), discr
!= 0)))
896 /// Set the discriminant for a new value of the given case of the given
898 pub fn trans_set_discr
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
<'tcx
>,
899 val
: ValueRef
, discr
: Disr
) {
901 CEnum(ity
, min
, max
) => {
902 assert_discr_in_range(ity
, min
, max
, discr
);
903 Store(bcx
, C_integral(ll_inttype(bcx
.ccx(), ity
), discr
as u64, true),
906 General(ity
, ref cases
, dtor
) => {
907 if dtor_active(dtor
) {
908 let ptr
= trans_field_ptr(bcx
, r
, val
, discr
,
909 cases
[discr
as usize].fields
.len() - 2);
910 Store(bcx
, C_u8(bcx
.ccx(), DTOR_NEEDED
as usize), ptr
);
912 Store(bcx
, C_integral(ll_inttype(bcx
.ccx(), ity
), discr
as u64, true),
913 GEPi(bcx
, val
, &[0, 0]));
915 Univariant(ref st
, dtor
) => {
916 assert_eq
!(discr
, 0);
917 if dtor_active(dtor
) {
918 Store(bcx
, C_u8(bcx
.ccx(), DTOR_NEEDED
as usize),
919 GEPi(bcx
, val
, &[0, st
.fields
.len() - 1]));
922 RawNullablePointer { nndiscr, nnty, ..}
=> {
923 if discr
!= nndiscr
{
924 let llptrty
= type_of
::sizing_type_of(bcx
.ccx(), nnty
);
925 Store(bcx
, C_null(llptrty
), val
);
928 StructWrappedNullablePointer { nndiscr, ref discrfield, .. }
=> {
929 if discr
!= nndiscr
{
930 let llptrptr
= GEPi(bcx
, val
, &discrfield
[..]);
931 let llptrty
= val_ty(llptrptr
).element_type();
932 Store(bcx
, C_null(llptrty
), llptrptr
);
938 fn assert_discr_in_range(ity
: IntType
, min
: Disr
, max
: Disr
, discr
: Disr
) {
940 attr
::UnsignedInt(_
) => assert
!(min
<= discr
&& discr
<= max
),
941 attr
::SignedInt(_
) => assert
!(min
as i64 <= discr
as i64 && discr
as i64 <= max
as i64)
945 /// The number of fields in a given case; for use when obtaining this
946 /// information from the type or definition is less convenient.
947 pub fn num_args(r
: &Repr
, discr
: Disr
) -> usize {
950 Univariant(ref st
, dtor
) => {
951 assert_eq
!(discr
, 0);
952 st
.fields
.len() - (if dtor_active(dtor
) { 1 }
else { 0 }
)
954 General(_
, ref cases
, dtor
) => {
955 cases
[discr
as usize].fields
.len() - 1 - (if dtor_active(dtor
) { 1 }
else { 0 }
)
957 RawNullablePointer { nndiscr, ref nullfields, .. }
=> {
958 if discr
== nndiscr { 1 }
else { nullfields.len() }
960 StructWrappedNullablePointer
{ ref nonnull
, nndiscr
,
961 ref nullfields
, .. } => {
962 if discr
== nndiscr { nonnull.fields.len() }
else { nullfields.len() }
967 /// Access a field, at a point when the value's case is known.
968 pub fn trans_field_ptr
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
<'tcx
>,
969 val
: ValueRef
, discr
: Disr
, ix
: usize) -> ValueRef
{
970 // Note: if this ever needs to generate conditionals (e.g., if we
971 // decide to do some kind of cdr-coding-like non-unique repr
972 // someday), it will need to return a possibly-new bcx as well.
975 bcx
.ccx().sess().bug("element access in C-like enum")
977 Univariant(ref st
, _dtor
) => {
978 assert_eq
!(discr
, 0);
979 struct_field_ptr(bcx
, st
, val
, ix
, false)
981 General(_
, ref cases
, _
) => {
982 struct_field_ptr(bcx
, &cases
[discr
as usize], val
, ix
+ 1, true)
984 RawNullablePointer { nndiscr, ref nullfields, .. }
|
985 StructWrappedNullablePointer { nndiscr, ref nullfields, .. }
if discr
!= nndiscr
=> {
986 // The unit-like case might have a nonzero number of unit-like fields.
987 // (e.d., Result of Either with (), as one side.)
988 let ty
= type_of
::type_of(bcx
.ccx(), nullfields
[ix
]);
989 assert_eq
!(machine
::llsize_of_alloc(bcx
.ccx(), ty
), 0);
990 // The contents of memory at this pointer can't matter, but use
991 // the value that's "reasonable" in case of pointer comparison.
992 PointerCast(bcx
, val
, ty
.ptr_to())
994 RawNullablePointer { nndiscr, nnty, .. }
=> {
996 assert_eq
!(discr
, nndiscr
);
997 let ty
= type_of
::type_of(bcx
.ccx(), nnty
);
998 PointerCast(bcx
, val
, ty
.ptr_to())
1000 StructWrappedNullablePointer { ref nonnull, nndiscr, .. }
=> {
1001 assert_eq
!(discr
, nndiscr
);
1002 struct_field_ptr(bcx
, nonnull
, val
, ix
, false)
1007 pub fn struct_field_ptr
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, st
: &Struct
<'tcx
>, val
: ValueRef
,
1008 ix
: usize, needs_cast
: bool
) -> ValueRef
{
1009 let val
= if needs_cast
{
1010 let ccx
= bcx
.ccx();
1011 let fields
= st
.fields
.iter().map(|&ty
| type_of
::type_of(ccx
, ty
)).collect
::<Vec
<_
>>();
1012 let real_ty
= Type
::struct_(ccx
, &fields
[..], st
.packed
);
1013 PointerCast(bcx
, val
, real_ty
.ptr_to())
1018 GEPi(bcx
, val
, &[0, ix
])
1021 pub fn fold_variants
<'blk
, 'tcx
, F
>(bcx
: Block
<'blk
, 'tcx
>,
1025 -> Block
<'blk
, 'tcx
> where
1026 F
: FnMut(Block
<'blk
, 'tcx
>, &Struct
<'tcx
>, ValueRef
) -> Block
<'blk
, 'tcx
>,
1030 Univariant(ref st
, _
) => {
1033 General(ity
, ref cases
, _
) => {
1034 let ccx
= bcx
.ccx();
1035 let unr_cx
= fcx
.new_temp_block("enum-variant-iter-unr");
1036 Unreachable(unr_cx
);
1038 let discr_val
= trans_get_discr(bcx
, r
, value
, None
);
1039 let llswitch
= Switch(bcx
, discr_val
, unr_cx
.llbb
, cases
.len());
1040 let bcx_next
= fcx
.new_temp_block("enum-variant-iter-next");
1042 for (discr
, case
) in cases
.iter().enumerate() {
1043 let mut variant_cx
= fcx
.new_temp_block(
1044 &format
!("enum-variant-iter-{}", &discr
.to_string())
1046 let rhs_val
= C_integral(ll_inttype(ccx
, ity
), discr
as u64, true);
1047 AddCase(llswitch
, rhs_val
, variant_cx
.llbb
);
1049 let fields
= case
.fields
.iter().map(|&ty
|
1050 type_of
::type_of(bcx
.ccx(), ty
)).collect
::<Vec
<_
>>();
1051 let real_ty
= Type
::struct_(ccx
, &fields
[..], case
.packed
);
1052 let variant_value
= PointerCast(variant_cx
, value
, real_ty
.ptr_to());
1054 variant_cx
= f(variant_cx
, case
, variant_value
);
1055 Br(variant_cx
, bcx_next
.llbb
, DebugLoc
::None
);
1064 /// Access the struct drop flag, if present.
1065 pub fn trans_drop_flag_ptr
<'blk
, 'tcx
>(mut bcx
: Block
<'blk
, 'tcx
>,
1068 -> datum
::DatumBlock
<'blk
, 'tcx
, datum
::Expr
>
1070 let tcx
= bcx
.tcx();
1071 let ptr_ty
= ty
::mk_imm_ptr(bcx
.tcx(), tcx
.dtor_type());
1073 Univariant(ref st
, dtor
) if dtor_active(dtor
) => {
1074 let flag_ptr
= GEPi(bcx
, val
, &[0, st
.fields
.len() - 1]);
1075 datum
::immediate_rvalue_bcx(bcx
, flag_ptr
, ptr_ty
).to_expr_datumblock()
1077 General(_
, _
, dtor
) if dtor_active(dtor
) => {
1079 let custom_cleanup_scope
= fcx
.push_custom_cleanup_scope();
1080 let scratch
= unpack_datum
!(bcx
, datum
::lvalue_scratch_datum(
1081 bcx
, tcx
.dtor_type(), "drop_flag",
1082 cleanup
::CustomScope(custom_cleanup_scope
), (), |_
, bcx
, _
| bcx
1084 bcx
= fold_variants(bcx
, r
, val
, |variant_cx
, st
, value
| {
1085 let ptr
= struct_field_ptr(variant_cx
, st
, value
, (st
.fields
.len() - 1), false);
1086 datum
::Datum
::new(ptr
, ptr_ty
, datum
::Lvalue
)
1087 .store_to(variant_cx
, scratch
.val
)
1089 let expr_datum
= scratch
.to_expr_datum();
1090 fcx
.pop_custom_cleanup_scope(custom_cleanup_scope
);
1091 datum
::DatumBlock
::new(bcx
, expr_datum
)
1093 _
=> bcx
.ccx().sess().bug("tried to get drop flag of non-droppable type")
1097 /// Construct a constant value, suitable for initializing a
1098 /// GlobalVariable, given a case and constant values for its fields.
1099 /// Note that this may have a different LLVM type (and different
1100 /// alignment!) from the representation's `type_of`, so it needs a
1101 /// pointer cast before use.
1103 /// The LLVM type system does not directly support unions, and only
1104 /// pointers can be bitcast, so a constant (and, by extension, the
1105 /// GlobalVariable initialized by it) will have a type that can vary
1106 /// depending on which case of an enum it is.
1108 /// To understand the alignment situation, consider `enum E { V64(u64),
1109 /// V32(u32, u32) }` on Windows. The type has 8-byte alignment to
1110 /// accommodate the u64, but `V32(x, y)` would have LLVM type `{i32,
1111 /// i32, i32}`, which is 4-byte aligned.
1113 /// Currently the returned value has the same size as the type, but
1114 /// this could be changed in the future to avoid allocating unnecessary
1115 /// space after values of shorter-than-maximum cases.
1116 pub fn trans_const
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>, r
: &Repr
<'tcx
>, discr
: Disr
,
1117 vals
: &[ValueRef
]) -> ValueRef
{
1119 CEnum(ity
, min
, max
) => {
1120 assert_eq
!(vals
.len(), 0);
1121 assert_discr_in_range(ity
, min
, max
, discr
);
1122 C_integral(ll_inttype(ccx
, ity
), discr
as u64, true)
1124 General(ity
, ref cases
, _
) => {
1125 let case
= &cases
[discr
as usize];
1126 let (max_sz
, _
) = union_size_and_align(&cases
[..]);
1127 let lldiscr
= C_integral(ll_inttype(ccx
, ity
), discr
as u64, true);
1128 let mut f
= vec
![lldiscr
];
1130 let mut contents
= build_const_struct(ccx
, case
, &f
[..]);
1131 contents
.push_all(&[padding(ccx
, max_sz
- case
.size
)]);
1132 C_struct(ccx
, &contents
[..], false)
1134 Univariant(ref st
, _dro
) => {
1135 assert
!(discr
== 0);
1136 let contents
= build_const_struct(ccx
, st
, vals
);
1137 C_struct(ccx
, &contents
[..], st
.packed
)
1139 RawNullablePointer { nndiscr, nnty, .. }
=> {
1140 if discr
== nndiscr
{
1141 assert_eq
!(vals
.len(), 1);
1144 C_null(type_of
::sizing_type_of(ccx
, nnty
))
1147 StructWrappedNullablePointer { ref nonnull, nndiscr, .. }
=> {
1148 if discr
== nndiscr
{
1149 C_struct(ccx
, &build_const_struct(ccx
,
1154 let vals
= nonnull
.fields
.iter().map(|&ty
| {
1155 // Always use null even if it's not the `discrfield`th
1156 // field; see #8506.
1157 C_null(type_of
::sizing_type_of(ccx
, ty
))
1158 }).collect
::<Vec
<ValueRef
>>();
1159 C_struct(ccx
, &build_const_struct(ccx
,
1168 /// Compute struct field offsets relative to struct begin.
1169 fn compute_struct_field_offsets
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>,
1170 st
: &Struct
<'tcx
>) -> Vec
<u64> {
1171 let mut offsets
= vec
!();
1174 for &ty
in &st
.fields
{
1175 let llty
= type_of
::sizing_type_of(ccx
, ty
);
1177 let type_align
= type_of
::align_of(ccx
, ty
);
1178 offset
= roundup(offset
, type_align
);
1180 offsets
.push(offset
);
1181 offset
+= machine
::llsize_of_alloc(ccx
, llty
);
1183 assert_eq
!(st
.fields
.len(), offsets
.len());
1187 /// Building structs is a little complicated, because we might need to
1188 /// insert padding if a field's value is less aligned than its type.
1190 /// Continuing the example from `trans_const`, a value of type `(u32,
1191 /// E)` should have the `E` at offset 8, but if that field's
1192 /// initializer is 4-byte aligned then simply translating the tuple as
1193 /// a two-element struct will locate it at offset 4, and accesses to it
1194 /// will read the wrong memory.
1195 fn build_const_struct
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>,
1196 st
: &Struct
<'tcx
>, vals
: &[ValueRef
])
1198 assert_eq
!(vals
.len(), st
.fields
.len());
1200 let target_offsets
= compute_struct_field_offsets(ccx
, st
);
1202 // offset of current value
1204 let mut cfields
= Vec
::new();
1205 for (&val
, &target_offset
) in vals
.iter().zip(target_offsets
.iter()) {
1207 let val_align
= machine
::llalign_of_min(ccx
, val_ty(val
));
1208 offset
= roundup(offset
, val_align
);
1210 if offset
!= target_offset
{
1211 cfields
.push(padding(ccx
, target_offset
- offset
));
1212 offset
= target_offset
;
1214 assert
!(!is_undef(val
));
1216 offset
+= machine
::llsize_of_alloc(ccx
, val_ty(val
));
1219 assert
!(st
.sized
&& offset
<= st
.size
);
1220 if offset
!= st
.size
{
1221 cfields
.push(padding(ccx
, st
.size
- offset
));
1227 fn padding(ccx
: &CrateContext
, size
: u64) -> ValueRef
{
1228 C_undef(Type
::array(&Type
::i8(ccx
), size
))
1231 // FIXME this utility routine should be somewhere more general
1233 fn roundup(x
: u64, a
: u32) -> u64 { let a = a as u64; ((x + (a - 1)) / a) * a }
1235 /// Get the discriminant of a constant value.
1236 pub fn const_get_discrim(ccx
: &CrateContext
, r
: &Repr
, val
: ValueRef
) -> Disr
{
1238 CEnum(ity
, _
, _
) => {
1240 attr
::SignedInt(..) => const_to_int(val
) as Disr
,
1241 attr
::UnsignedInt(..) => const_to_uint(val
) as Disr
1244 General(ity
, _
, _
) => {
1246 attr
::SignedInt(..) => const_to_int(const_get_elt(ccx
, val
, &[0])) as Disr
,
1247 attr
::UnsignedInt(..) => const_to_uint(const_get_elt(ccx
, val
, &[0])) as Disr
1250 Univariant(..) => 0,
1251 RawNullablePointer { .. }
| StructWrappedNullablePointer { .. }
=> {
1252 ccx
.sess().bug("const discrim access of non c-like enum")
1257 /// Extract a field of a constant value, as appropriate for its
1260 /// (Not to be confused with `common::const_get_elt`, which operates on
1261 /// raw LLVM-level structs and arrays.)
1262 pub fn const_get_field(ccx
: &CrateContext
, r
: &Repr
, val
: ValueRef
,
1263 _discr
: Disr
, ix
: usize) -> ValueRef
{
1265 CEnum(..) => ccx
.sess().bug("element access in C-like enum const"),
1266 Univariant(..) => const_struct_field(ccx
, val
, ix
),
1267 General(..) => const_struct_field(ccx
, val
, ix
+ 1),
1268 RawNullablePointer { .. }
=> {
1272 StructWrappedNullablePointer{ .. }
=> const_struct_field(ccx
, val
, ix
)
1276 /// Extract field of struct-like const, skipping our alignment padding.
1277 fn const_struct_field(ccx
: &CrateContext
, val
: ValueRef
, ix
: usize) -> ValueRef
{
1278 // Get the ix-th non-undef element of the struct.
1279 let mut real_ix
= 0; // actual position in the struct
1280 let mut ix
= ix
; // logical index relative to real_ix
1284 field
= const_get_elt(ccx
, val
, &[real_ix
]);
1285 if !is_undef(field
) {
1288 real_ix
= real_ix
+ 1;
1294 real_ix
= real_ix
+ 1;