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
::*;
52 use llvm
::{ValueRef, True, IntEQ, IntNE}
;
53 use back
::abi
::FAT_PTR_ADDR
;
55 use middle
::ty
::{self, Ty, ClosureTyper}
;
59 use syntax
::attr
::IntType
;
63 use trans
::cleanup
::CleanupMethods
;
66 use trans
::debuginfo
::DebugLoc
;
68 use trans
::monomorphize
;
69 use trans
::type_
::Type
;
71 use util
::ppaux
::ty_to_string
;
73 type Hint
= attr
::ReprAttr
;
76 #[derive(Eq, PartialEq, Debug)]
78 /// C-like enums; basically an int.
79 CEnum(IntType
, Disr
, Disr
), // discriminant range (signedness based on the IntType)
80 /// Single-case variants, and structs/tuples/records.
82 /// Structs with destructors need a dynamic destroyedness flag to
83 /// avoid running the destructor too many times; this is included
84 /// in the `Struct` if present.
85 /// (The flag if nonzero, represents the initialization value to use;
86 /// if zero, then use no flag at all.)
87 Univariant(Struct
<'tcx
>, u8),
88 /// General-case enums: for each case there is a struct, and they
89 /// all start with a field for the discriminant.
91 /// Types with destructors need a dynamic destroyedness flag to
92 /// avoid running the destructor too many times; the last argument
93 /// indicates whether such a flag is present.
94 /// (The flag, if nonzero, represents the initialization value to use;
95 /// if zero, then use no flag at all.)
96 General(IntType
, Vec
<Struct
<'tcx
>>, u8),
97 /// Two cases distinguished by a nullable pointer: the case with discriminant
98 /// `nndiscr` must have single field which is known to be nonnull due to its type.
99 /// The other case is known to be zero sized. Hence we represent the enum
100 /// as simply a nullable pointer: if not null it indicates the `nndiscr` variant,
101 /// otherwise it indicates the other case.
105 nullfields
: Vec
<Ty
<'tcx
>>
107 /// Two cases distinguished by a nullable pointer: the case with discriminant
108 /// `nndiscr` is represented by the struct `nonnull`, where the `discrfield`th
109 /// field is known to be nonnull due to its type; if that field is null, then
110 /// it represents the other case, which is inhabited by at most one value
111 /// (and all other fields are undefined/unused).
113 /// For example, `std::option::Option` instantiated at a safe pointer type
114 /// is represented such that `None` is a null pointer and `Some` is the
115 /// identity function.
116 StructWrappedNullablePointer
{
117 nonnull
: Struct
<'tcx
>,
119 discrfield
: DiscrField
,
120 nullfields
: Vec
<Ty
<'tcx
>>,
124 /// For structs, and struct-like parts of anything fancier.
125 #[derive(Eq, PartialEq, Debug)]
126 pub struct Struct
<'tcx
> {
127 // If the struct is DST, then the size and alignment do not take into
128 // account the unsized fields of the struct.
133 pub fields
: Vec
<Ty
<'tcx
>>
136 /// Convenience for `represent_type`. There should probably be more or
137 /// these, for places in trans where the `Ty` isn't directly
139 pub fn represent_node
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>,
140 node
: ast
::NodeId
) -> Rc
<Repr
<'tcx
>> {
141 represent_type(bcx
.ccx(), node_id_type(bcx
, node
))
144 /// Decides how to represent a given type.
145 pub fn represent_type
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
146 t
: Ty
<'tcx
>) -> Rc
<Repr
<'tcx
>> {
147 debug
!("Representing: {}", ty_to_string(cx
.tcx(), t
));
148 match cx
.adt_reprs().borrow().get(&t
) {
149 Some(repr
) => return repr
.clone(),
153 let repr
= Rc
::new(represent_type_uncached(cx
, t
));
154 debug
!("Represented as: {:?}", repr
);
155 cx
.adt_reprs().borrow_mut().insert(t
, repr
.clone());
159 macro_rules
! repeat_u8_as_u32
{
160 ($name
:expr
) => { (($name
as u32) << 24 |
161 ($name
as u32) << 16 |
162 ($name
as u32) << 8 |
165 macro_rules
! repeat_u8_as_u64
{
166 ($name
:expr
) => { ((repeat_u8_as_u32
!($name
) as u64) << 32 |
167 (repeat_u8_as_u32
!($name
) as u64)) }
170 pub const DTOR_NEEDED
: u8 = 0xd4;
171 pub const DTOR_NEEDED_U32
: u32 = repeat_u8_as_u32
!(DTOR_NEEDED
);
172 pub const DTOR_NEEDED_U64
: u64 = repeat_u8_as_u64
!(DTOR_NEEDED
);
174 pub fn dtor_needed_usize(ccx
: &CrateContext
) -> usize {
175 match &ccx
.tcx().sess
.target
.target
.target_pointer_width
[..] {
176 "32" => DTOR_NEEDED_U32
as usize,
177 "64" => DTOR_NEEDED_U64
as usize,
178 tws
=> panic
!("Unsupported target word size for int: {}", tws
),
182 pub const DTOR_DONE
: u8 = 0x1d;
183 pub const DTOR_DONE_U32
: u32 = repeat_u8_as_u32
!(DTOR_DONE
);
184 pub const DTOR_DONE_U64
: u64 = repeat_u8_as_u64
!(DTOR_DONE
);
186 pub fn dtor_done_usize(ccx
: &CrateContext
) -> usize {
187 match &ccx
.tcx().sess
.target
.target
.target_pointer_width
[..] {
188 "32" => DTOR_DONE_U32
as usize,
189 "64" => DTOR_DONE_U64
as usize,
190 tws
=> panic
!("Unsupported target word size for int: {}", tws
),
194 fn dtor_to_init_u8(dtor
: bool
) -> u8 {
195 if dtor { DTOR_NEEDED }
else { 0 }
198 pub trait GetDtorType
<'tcx
> { fn dtor_type(&self) -> Ty<'tcx>; }
199 impl<'tcx
> GetDtorType
<'tcx
> for ty
::ctxt
<'tcx
> {
200 fn dtor_type(&self) -> Ty
<'tcx
> { self.types.u8 }
203 fn dtor_active(flag
: u8) -> bool
{
207 fn represent_type_uncached
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
208 t
: Ty
<'tcx
>) -> Repr
<'tcx
> {
210 ty
::ty_tup(ref elems
) => {
211 Univariant(mk_struct(cx
, &elems
[..], false, t
), 0)
213 ty
::ty_struct(def_id
, substs
) => {
214 let fields
= ty
::lookup_struct_fields(cx
.tcx(), def_id
);
215 let mut ftys
= fields
.iter().map(|field
| {
216 let fty
= ty
::lookup_field_type(cx
.tcx(), def_id
, field
.id
, substs
);
217 monomorphize
::normalize_associated_type(cx
.tcx(), &fty
)
218 }).collect
::<Vec
<_
>>();
219 let packed
= ty
::lookup_packed(cx
.tcx(), def_id
);
220 let dtor
= ty
::ty_dtor(cx
.tcx(), def_id
).has_drop_flag();
221 if dtor { ftys.push(cx.tcx().dtor_type()); }
223 Univariant(mk_struct(cx
, &ftys
[..], packed
, t
), dtor_to_init_u8(dtor
))
225 ty
::ty_closure(def_id
, substs
) => {
226 let typer
= NormalizingClosureTyper
::new(cx
.tcx());
227 let upvars
= typer
.closure_upvars(def_id
, substs
).unwrap();
228 let upvar_types
= upvars
.iter().map(|u
| u
.ty
).collect
::<Vec
<_
>>();
229 Univariant(mk_struct(cx
, &upvar_types
[..], false, t
), 0)
231 ty
::ty_enum(def_id
, substs
) => {
232 let cases
= get_cases(cx
.tcx(), def_id
, substs
);
233 let hint
= *ty
::lookup_repr_hints(cx
.tcx(), def_id
).get(0)
234 .unwrap_or(&attr
::ReprAny
);
236 let dtor
= ty
::ty_dtor(cx
.tcx(), def_id
).has_drop_flag();
238 if cases
.len() == 0 {
239 // Uninhabitable; represent as unit
240 // (Typechecking will reject discriminant-sizing attrs.)
241 assert_eq
!(hint
, attr
::ReprAny
);
242 let ftys
= if dtor { vec!(cx.tcx().dtor_type()) }
else { vec!() }
;
243 return Univariant(mk_struct(cx
, &ftys
[..], false, t
),
244 dtor_to_init_u8(dtor
));
247 if !dtor
&& cases
.iter().all(|c
| c
.tys
.len() == 0) {
248 // All bodies empty -> intlike
249 let discrs
: Vec
<u64> = cases
.iter().map(|c
| c
.discr
).collect();
250 let bounds
= IntBounds
{
251 ulo
: *discrs
.iter().min().unwrap(),
252 uhi
: *discrs
.iter().max().unwrap(),
253 slo
: discrs
.iter().map(|n
| *n
as i64).min().unwrap(),
254 shi
: discrs
.iter().map(|n
| *n
as i64).max().unwrap()
256 return mk_cenum(cx
, hint
, &bounds
);
259 // Since there's at least one
260 // non-empty body, explicit discriminants should have
261 // been rejected by a checker before this point.
262 if !cases
.iter().enumerate().all(|(i
,c
)| c
.discr
== (i
as Disr
)) {
263 cx
.sess().bug(&format
!("non-C-like enum {} with specified \
265 ty
::item_path_str(cx
.tcx(),
269 if cases
.len() == 1 {
270 // Equivalent to a struct/tuple/newtype.
271 // (Typechecking will reject discriminant-sizing attrs.)
272 assert_eq
!(hint
, attr
::ReprAny
);
273 let mut ftys
= cases
[0].tys
.clone();
274 if dtor { ftys.push(cx.tcx().dtor_type()); }
275 return Univariant(mk_struct(cx
, &ftys
[..], false, t
),
276 dtor_to_init_u8(dtor
));
279 if !dtor
&& cases
.len() == 2 && hint
== attr
::ReprAny
{
280 // Nullable pointer optimization
283 if cases
[1 - discr
].is_zerolen(cx
, t
) {
284 let st
= mk_struct(cx
, &cases
[discr
].tys
,
286 match cases
[discr
].find_ptr(cx
) {
287 Some(ref df
) if df
.len() == 1 && st
.fields
.len() == 1 => {
288 return RawNullablePointer
{
289 nndiscr
: discr
as Disr
,
291 nullfields
: cases
[1 - discr
].tys
.clone()
294 Some(mut discrfield
) => {
296 discrfield
.reverse();
297 return StructWrappedNullablePointer
{
298 nndiscr
: discr
as Disr
,
300 discrfield
: discrfield
,
301 nullfields
: cases
[1 - discr
].tys
.clone()
312 assert
!((cases
.len() - 1) as i64 >= 0);
313 let bounds
= IntBounds
{ ulo
: 0, uhi
: (cases
.len() - 1) as u64,
314 slo
: 0, shi
: (cases
.len() - 1) as i64 };
315 let min_ity
= range_to_inttype(cx
, hint
, &bounds
);
317 // Create the set of structs that represent each variant
318 // Use the minimum integer type we figured out above
319 let fields
: Vec
<_
> = cases
.iter().map(|c
| {
320 let mut ftys
= vec
!(ty_of_inttype(cx
.tcx(), min_ity
));
321 ftys
.push_all(&c
.tys
);
322 if dtor { ftys.push(cx.tcx().dtor_type()); }
323 mk_struct(cx
, &ftys
, false, t
)
327 // Check to see if we should use a different type for the
328 // discriminant. If the overall alignment of the type is
329 // the same as the first field in each variant, we can safely use
330 // an alignment-sized type.
331 // We increase the size of the discriminant to avoid LLVM copying
332 // padding when it doesn't need to. This normally causes unaligned
333 // load/stores and excessive memcpy/memset operations. By using a
334 // bigger integer size, LLVM can be sure about it's contents and
335 // won't be so conservative.
336 // This check is needed to avoid increasing the size of types when
337 // the alignment of the first field is smaller than the overall
338 // alignment of the type.
339 let (_
, align
) = union_size_and_align(&fields
);
340 let mut use_align
= true;
342 // Get the first non-zero-sized field
343 let field
= st
.fields
.iter().skip(1).filter(|ty
| {
344 let t
= type_of
::sizing_type_of(cx
, **ty
);
345 machine
::llsize_of_real(cx
, t
) != 0 ||
346 // This case is only relevant for zero-sized types with large alignment
347 machine
::llalign_of_min(cx
, t
) != 1
350 if let Some(field
) = field
{
351 let field_align
= type_of
::align_of(cx
, *field
);
352 if field_align
!= align
{
358 let ity
= if use_align
{
359 // Use the overall alignment
361 1 => attr
::UnsignedInt(ast
::TyU8
),
362 2 => attr
::UnsignedInt(ast
::TyU16
),
363 4 => attr
::UnsignedInt(ast
::TyU32
),
364 8 if machine
::llalign_of_min(cx
, Type
::i64(cx
)) == 8 =>
365 attr
::UnsignedInt(ast
::TyU64
),
366 _
=> min_ity
// use min_ity as a fallback
372 let fields
: Vec
<_
> = cases
.iter().map(|c
| {
373 let mut ftys
= vec
!(ty_of_inttype(cx
.tcx(), ity
));
374 ftys
.push_all(&c
.tys
);
375 if dtor { ftys.push(cx.tcx().dtor_type()); }
376 mk_struct(cx
, &ftys
[..], false, t
)
379 ensure_enum_fits_in_address_space(cx
, &fields
[..], t
);
381 General(ity
, fields
, dtor_to_init_u8(dtor
))
383 _
=> cx
.sess().bug(&format
!("adt::represent_type called on non-ADT type: {}",
384 ty_to_string(cx
.tcx(), t
)))
388 // this should probably all be in ty
394 /// This represents the (GEP) indices to follow to get to the discriminant field
395 pub type DiscrField
= Vec
<usize>;
397 fn find_discr_field_candidate
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>,
399 mut path
: DiscrField
) -> Option
<DiscrField
> {
401 // Fat &T/&mut T/Box<T> i.e. T is [T], str, or Trait
402 ty
::ty_rptr(_
, ty
::mt { ty, .. }
) | ty
::ty_uniq(ty
) if !type_is_sized(tcx
, ty
) => {
403 path
.push(FAT_PTR_ADDR
);
407 // Regular thin pointer: &T/&mut T/Box<T>
408 ty
::ty_rptr(..) | ty
::ty_uniq(..) => Some(path
),
410 // Functions are just pointers
411 ty
::ty_bare_fn(..) => Some(path
),
413 // Is this the NonZero lang item wrapping a pointer or integer type?
414 ty
::ty_struct(did
, substs
) if Some(did
) == tcx
.lang_items
.non_zero() => {
415 let nonzero_fields
= ty
::lookup_struct_fields(tcx
, did
);
416 assert_eq
!(nonzero_fields
.len(), 1);
417 let nonzero_field
= ty
::lookup_field_type(tcx
, did
, nonzero_fields
[0].id
, substs
);
418 match nonzero_field
.sty
{
419 ty
::ty_ptr(..) | ty
::ty_int(..) | ty
::ty_uint(..) => {
427 // Perhaps one of the fields of this struct is non-zero
428 // let's recurse and find out
429 ty
::ty_struct(def_id
, substs
) => {
430 let fields
= ty
::lookup_struct_fields(tcx
, def_id
);
431 for (j
, field
) in fields
.iter().enumerate() {
432 let field_ty
= ty
::lookup_field_type(tcx
, def_id
, field
.id
, substs
);
433 if let Some(mut fpath
) = find_discr_field_candidate(tcx
, field_ty
, path
.clone()) {
441 // Can we use one of the fields in this tuple?
442 ty
::ty_tup(ref tys
) => {
443 for (j
, &ty
) in tys
.iter().enumerate() {
444 if let Some(mut fpath
) = find_discr_field_candidate(tcx
, ty
, path
.clone()) {
452 // Is this a fixed-size array of something non-zero
453 // with at least one element?
454 ty
::ty_vec(ety
, Some(d
)) if d
> 0 => {
455 if let Some(mut vpath
) = find_discr_field_candidate(tcx
, ety
, path
) {
463 // Anything else is not a pointer
468 impl<'tcx
> Case
<'tcx
> {
469 fn is_zerolen
<'a
>(&self, cx
: &CrateContext
<'a
, 'tcx
>, scapegoat
: Ty
<'tcx
>) -> bool
{
470 mk_struct(cx
, &self.tys
, false, scapegoat
).size
== 0
473 fn find_ptr
<'a
>(&self, cx
: &CrateContext
<'a
, 'tcx
>) -> Option
<DiscrField
> {
474 for (i
, &ty
) in self.tys
.iter().enumerate() {
475 if let Some(mut path
) = find_discr_field_candidate(cx
.tcx(), ty
, vec
![]) {
484 fn get_cases
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>,
486 substs
: &subst
::Substs
<'tcx
>)
488 ty
::enum_variants(tcx
, def_id
).iter().map(|vi
| {
489 let arg_tys
= vi
.args
.iter().map(|&raw_ty
| {
490 monomorphize
::apply_param_substs(tcx
, substs
, &raw_ty
)
492 Case { discr: vi.disr_val, tys: arg_tys }
496 fn mk_struct
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
497 tys
: &[Ty
<'tcx
>], packed
: bool
,
500 let sized
= tys
.iter().all(|&ty
| type_is_sized(cx
.tcx(), ty
));
501 let lltys
: Vec
<Type
> = if sized
{
503 .map(|&ty
| type_of
::sizing_type_of(cx
, ty
)).collect()
505 tys
.iter().filter(|&ty
| type_is_sized(cx
.tcx(), *ty
))
506 .map(|&ty
| type_of
::sizing_type_of(cx
, ty
)).collect()
509 ensure_struct_fits_in_address_space(cx
, &lltys
[..], packed
, scapegoat
);
511 let llty_rec
= Type
::struct_(cx
, &lltys
[..], packed
);
513 size
: machine
::llsize_of_alloc(cx
, llty_rec
),
514 align
: machine
::llalign_of_min(cx
, llty_rec
),
517 fields
: tys
.to_vec(),
529 fn mk_cenum
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
530 hint
: Hint
, bounds
: &IntBounds
)
532 let it
= range_to_inttype(cx
, hint
, bounds
);
534 attr
::SignedInt(_
) => CEnum(it
, bounds
.slo
as Disr
, bounds
.shi
as Disr
),
535 attr
::UnsignedInt(_
) => CEnum(it
, bounds
.ulo
, bounds
.uhi
)
539 fn range_to_inttype(cx
: &CrateContext
, hint
: Hint
, bounds
: &IntBounds
) -> IntType
{
540 debug
!("range_to_inttype: {:?} {:?}", hint
, bounds
);
541 // Lists of sizes to try. u64 is always allowed as a fallback.
542 #[allow(non_upper_case_globals)]
543 const choose_shortest
: &'
static [IntType
] = &[
544 attr
::UnsignedInt(ast
::TyU8
), attr
::SignedInt(ast
::TyI8
),
545 attr
::UnsignedInt(ast
::TyU16
), attr
::SignedInt(ast
::TyI16
),
546 attr
::UnsignedInt(ast
::TyU32
), attr
::SignedInt(ast
::TyI32
)];
547 #[allow(non_upper_case_globals)]
548 const at_least_32
: &'
static [IntType
] = &[
549 attr
::UnsignedInt(ast
::TyU32
), attr
::SignedInt(ast
::TyI32
)];
553 attr
::ReprInt(span
, ity
) => {
554 if !bounds_usable(cx
, ity
, bounds
) {
555 cx
.sess().span_bug(span
, "representation hint insufficient for discriminant range")
559 attr
::ReprExtern
=> {
560 attempts
= match &cx
.sess().target
.target
.arch
[..] {
561 // WARNING: the ARM EABI has two variants; the one corresponding to `at_least_32`
562 // appears to be used on Linux and NetBSD, but some systems may use the variant
563 // corresponding to `choose_shortest`. However, we don't run on those yet...?
564 "arm" => at_least_32
,
569 attempts
= choose_shortest
;
571 attr
::ReprPacked
=> {
572 cx
.tcx().sess
.bug("range_to_inttype: found ReprPacked on an enum");
575 for &ity
in attempts
{
576 if bounds_usable(cx
, ity
, bounds
) {
580 return attr
::UnsignedInt(ast
::TyU64
);
583 pub fn ll_inttype(cx
: &CrateContext
, ity
: IntType
) -> Type
{
585 attr
::SignedInt(t
) => Type
::int_from_ty(cx
, t
),
586 attr
::UnsignedInt(t
) => Type
::uint_from_ty(cx
, t
)
590 fn bounds_usable(cx
: &CrateContext
, ity
: IntType
, bounds
: &IntBounds
) -> bool
{
591 debug
!("bounds_usable: {:?} {:?}", ity
, bounds
);
593 attr
::SignedInt(_
) => {
594 let lllo
= C_integral(ll_inttype(cx
, ity
), bounds
.slo
as u64, true);
595 let llhi
= C_integral(ll_inttype(cx
, ity
), bounds
.shi
as u64, true);
596 bounds
.slo
== const_to_int(lllo
) as i64 && bounds
.shi
== const_to_int(llhi
) as i64
598 attr
::UnsignedInt(_
) => {
599 let lllo
= C_integral(ll_inttype(cx
, ity
), bounds
.ulo
, false);
600 let llhi
= C_integral(ll_inttype(cx
, ity
), bounds
.uhi
, false);
601 bounds
.ulo
== const_to_uint(lllo
) as u64 && bounds
.uhi
== const_to_uint(llhi
) as u64
606 pub fn ty_of_inttype
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>, ity
: IntType
) -> Ty
<'tcx
> {
608 attr
::SignedInt(t
) => ty
::mk_mach_int(tcx
, t
),
609 attr
::UnsignedInt(t
) => ty
::mk_mach_uint(tcx
, t
)
613 // LLVM doesn't like types that don't fit in the address space
614 fn ensure_struct_fits_in_address_space
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>,
617 scapegoat
: Ty
<'tcx
>) {
619 for &llty
in fields
{
620 // Invariant: offset < ccx.obj_size_bound() <= 1<<61
622 let type_align
= machine
::llalign_of_min(ccx
, llty
);
623 offset
= roundup(offset
, type_align
);
625 // type_align is a power-of-2, so still offset < ccx.obj_size_bound()
626 // llsize_of_alloc(ccx, llty) is also less than ccx.obj_size_bound()
627 // so the sum is less than 1<<62 (and therefore can't overflow).
628 offset
+= machine
::llsize_of_alloc(ccx
, llty
);
630 if offset
>= ccx
.obj_size_bound() {
631 ccx
.report_overbig_object(scapegoat
);
636 fn union_size_and_align(sts
: &[Struct
]) -> (machine
::llsize
, machine
::llalign
) {
637 let size
= sts
.iter().map(|st
| st
.size
).max().unwrap();
638 let align
= sts
.iter().map(|st
| st
.align
).max().unwrap();
639 (roundup(size
, align
), align
)
642 fn ensure_enum_fits_in_address_space
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>,
644 scapegoat
: Ty
<'tcx
>) {
645 let (total_size
, _
) = union_size_and_align(fields
);
647 if total_size
>= ccx
.obj_size_bound() {
648 ccx
.report_overbig_object(scapegoat
);
653 /// LLVM-level types are a little complicated.
655 /// C-like enums need to be actual ints, not wrapped in a struct,
656 /// because that changes the ABI on some platforms (see issue #10308).
658 /// For nominal types, in some cases, we need to use LLVM named structs
659 /// and fill in the actual contents in a second pass to prevent
660 /// unbounded recursion; see also the comments in `trans::type_of`.
661 pub fn type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>, r
: &Repr
<'tcx
>) -> Type
{
662 generic_type_of(cx
, r
, None
, false, false)
664 // Pass dst=true if the type you are passing is a DST. Yes, we could figure
665 // this out, but if you call this on an unsized type without realising it, you
666 // are going to get the wrong type (it will not include the unsized parts of it).
667 pub fn sizing_type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
668 r
: &Repr
<'tcx
>, dst
: bool
) -> Type
{
669 generic_type_of(cx
, r
, None
, true, dst
)
671 pub fn incomplete_type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
672 r
: &Repr
<'tcx
>, name
: &str) -> Type
{
673 generic_type_of(cx
, r
, Some(name
), false, false)
675 pub fn finish_type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
676 r
: &Repr
<'tcx
>, llty
: &mut Type
) {
678 CEnum(..) | General(..) | RawNullablePointer { .. }
=> { }
679 Univariant(ref st
, _
) | StructWrappedNullablePointer { nonnull: ref st, .. }
=>
680 llty
.set_struct_body(&struct_llfields(cx
, st
, false, false),
685 fn generic_type_of
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>,
691 CEnum(ity
, _
, _
) => ll_inttype(cx
, ity
),
692 RawNullablePointer { nnty, .. }
=> type_of
::sizing_type_of(cx
, nnty
),
693 Univariant(ref st
, _
) | StructWrappedNullablePointer { nonnull: ref st, .. }
=> {
696 Type
::struct_(cx
, &struct_llfields(cx
, st
, sizing
, dst
),
699 Some(name
) => { assert_eq!(sizing, false); Type::named_struct(cx, name) }
702 General(ity
, ref sts
, _
) => {
703 // We need a representation that has:
704 // * The alignment of the most-aligned field
705 // * The size of the largest variant (rounded up to that alignment)
706 // * No alignment padding anywhere any variant has actual data
707 // (currently matters only for enums small enough to be immediate)
708 // * The discriminant in an obvious place.
710 // So we start with the discriminant, pad it up to the alignment with
711 // more of its own type, then use alignment-sized ints to get the rest
714 // FIXME #10604: this breaks when vector types are present.
715 let (size
, align
) = union_size_and_align(&sts
[..]);
716 let align_s
= align
as u64;
717 assert_eq
!(size
% align_s
, 0);
718 let align_units
= size
/ align_s
- 1;
720 let discr_ty
= ll_inttype(cx
, ity
);
721 let discr_size
= machine
::llsize_of_alloc(cx
, discr_ty
);
722 let fill_ty
= match align_s
{
723 1 => Type
::array(&Type
::i8(cx
), align_units
),
724 2 => Type
::array(&Type
::i16(cx
), align_units
),
725 4 => Type
::array(&Type
::i32(cx
), align_units
),
726 8 if machine
::llalign_of_min(cx
, Type
::i64(cx
)) == 8 =>
727 Type
::array(&Type
::i64(cx
), align_units
),
728 a
if a
.count_ones() == 1 => Type
::array(&Type
::vector(&Type
::i32(cx
), a
/ 4),
730 _
=> panic
!("unsupported enum alignment: {}", align
)
732 assert_eq
!(machine
::llalign_of_min(cx
, fill_ty
), align
);
733 assert_eq
!(align_s
% discr_size
, 0);
734 let fields
= [discr_ty
,
735 Type
::array(&discr_ty
, align_s
/ discr_size
- 1),
738 None
=> Type
::struct_(cx
, &fields
[..], false),
740 let mut llty
= Type
::named_struct(cx
, name
);
741 llty
.set_struct_body(&fields
[..], false);
749 fn struct_llfields
<'a
, 'tcx
>(cx
: &CrateContext
<'a
, 'tcx
>, st
: &Struct
<'tcx
>,
750 sizing
: bool
, dst
: bool
) -> Vec
<Type
> {
752 st
.fields
.iter().filter(|&ty
| !dst
|| type_is_sized(cx
.tcx(), *ty
))
753 .map(|&ty
| type_of
::sizing_type_of(cx
, ty
)).collect()
755 st
.fields
.iter().map(|&ty
| type_of
::in_memory_type_of(cx
, ty
)).collect()
759 /// Obtain a representation of the discriminant sufficient to translate
760 /// destructuring; this may or may not involve the actual discriminant.
762 /// This should ideally be less tightly tied to `_match`.
763 pub fn trans_switch
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>,
764 r
: &Repr
<'tcx
>, scrutinee
: ValueRef
)
765 -> (_match
::BranchKind
, Option
<ValueRef
>) {
767 CEnum(..) | General(..) |
768 RawNullablePointer { .. }
| StructWrappedNullablePointer { .. }
=> {
769 (_match
::Switch
, Some(trans_get_discr(bcx
, r
, scrutinee
, None
)))
772 (_match
::Single
, None
)
779 /// Obtain the actual discriminant of a value.
780 pub fn trans_get_discr
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
<'tcx
>,
781 scrutinee
: ValueRef
, cast_to
: Option
<Type
>)
785 debug
!("trans_get_discr r: {:?}", r
);
787 CEnum(ity
, min
, max
) => {
788 val
= load_discr(bcx
, ity
, scrutinee
, min
, max
);
789 signed
= ity
.is_signed();
791 General(ity
, ref cases
, _
) => {
792 let ptr
= GEPi(bcx
, scrutinee
, &[0, 0]);
793 val
= load_discr(bcx
, ity
, ptr
, 0, (cases
.len() - 1) as Disr
);
794 signed
= ity
.is_signed();
797 val
= C_u8(bcx
.ccx(), 0);
800 RawNullablePointer { nndiscr, nnty, .. }
=> {
801 let cmp
= if nndiscr
== 0 { IntEQ }
else { IntNE }
;
802 let llptrty
= type_of
::sizing_type_of(bcx
.ccx(), nnty
);
803 val
= ICmp(bcx
, cmp
, Load(bcx
, scrutinee
), C_null(llptrty
), DebugLoc
::None
);
806 StructWrappedNullablePointer { nndiscr, ref discrfield, .. }
=> {
807 val
= struct_wrapped_nullable_bitdiscr(bcx
, nndiscr
, discrfield
, scrutinee
);
813 Some(llty
) => if signed { SExt(bcx, val, llty) }
else { ZExt(bcx, val, llty) }
817 fn struct_wrapped_nullable_bitdiscr(bcx
: Block
, nndiscr
: Disr
, discrfield
: &DiscrField
,
818 scrutinee
: ValueRef
) -> ValueRef
{
819 let llptrptr
= GEPi(bcx
, scrutinee
, &discrfield
[..]);
820 let llptr
= Load(bcx
, llptrptr
);
821 let cmp
= if nndiscr
== 0 { IntEQ }
else { IntNE }
;
822 ICmp(bcx
, cmp
, llptr
, C_null(val_ty(llptr
)), DebugLoc
::None
)
825 /// Helper for cases where the discriminant is simply loaded.
826 fn load_discr(bcx
: Block
, ity
: IntType
, ptr
: ValueRef
, min
: Disr
, max
: Disr
)
828 let llty
= ll_inttype(bcx
.ccx(), ity
);
829 assert_eq
!(val_ty(ptr
), llty
.ptr_to());
830 let bits
= machine
::llbitsize_of_real(bcx
.ccx(), llty
);
832 let bits
= bits
as usize;
833 let mask
= (!0u64 >> (64 - bits
)) as Disr
;
834 // For a (max) discr of -1, max will be `-1 as usize`, which overflows.
835 // However, that is fine here (it would still represent the full range),
836 if (max
.wrapping_add(1)) & mask
== min
& mask
{
837 // i.e., if the range is everything. The lo==hi case would be
838 // rejected by the LLVM verifier (it would mean either an
839 // empty set, which is impossible, or the entire range of the
840 // type, which is pointless).
843 // llvm::ConstantRange can deal with ranges that wrap around,
844 // so an overflow on (max + 1) is fine.
845 LoadRangeAssert(bcx
, ptr
, min
, (max
.wrapping_add(1)), /* signed: */ True
)
849 /// Yield information about how to dispatch a case of the
850 /// discriminant-like value returned by `trans_switch`.
852 /// This should ideally be less tightly tied to `_match`.
853 pub fn trans_case
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
, discr
: Disr
)
854 -> _match
::OptResult
<'blk
, 'tcx
> {
856 CEnum(ity
, _
, _
) => {
857 _match
::SingleResult(Result
::new(bcx
, C_integral(ll_inttype(bcx
.ccx(), ity
),
858 discr
as u64, true)))
860 General(ity
, _
, _
) => {
861 _match
::SingleResult(Result
::new(bcx
, C_integral(ll_inttype(bcx
.ccx(), ity
),
862 discr
as u64, true)))
865 bcx
.ccx().sess().bug("no cases for univariants or structs")
867 RawNullablePointer { .. }
|
868 StructWrappedNullablePointer { .. }
=> {
869 assert
!(discr
== 0 || discr
== 1);
870 _match
::SingleResult(Result
::new(bcx
, C_bool(bcx
.ccx(), discr
!= 0)))
875 /// Set the discriminant for a new value of the given case of the given
877 pub fn trans_set_discr
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
<'tcx
>,
878 val
: ValueRef
, discr
: Disr
) {
880 CEnum(ity
, min
, max
) => {
881 assert_discr_in_range(ity
, min
, max
, discr
);
882 Store(bcx
, C_integral(ll_inttype(bcx
.ccx(), ity
), discr
as u64, true),
885 General(ity
, ref cases
, dtor
) => {
886 if dtor_active(dtor
) {
887 let ptr
= trans_field_ptr(bcx
, r
, val
, discr
,
888 cases
[discr
as usize].fields
.len() - 2);
889 Store(bcx
, C_u8(bcx
.ccx(), DTOR_NEEDED
as usize), ptr
);
891 Store(bcx
, C_integral(ll_inttype(bcx
.ccx(), ity
), discr
as u64, true),
892 GEPi(bcx
, val
, &[0, 0]))
894 Univariant(ref st
, dtor
) => {
895 assert_eq
!(discr
, 0);
896 if dtor_active(dtor
) {
897 Store(bcx
, C_u8(bcx
.ccx(), DTOR_NEEDED
as usize),
898 GEPi(bcx
, val
, &[0, st
.fields
.len() - 1]));
901 RawNullablePointer { nndiscr, nnty, ..}
=> {
902 if discr
!= nndiscr
{
903 let llptrty
= type_of
::sizing_type_of(bcx
.ccx(), nnty
);
904 Store(bcx
, C_null(llptrty
), val
)
907 StructWrappedNullablePointer { nndiscr, ref discrfield, .. }
=> {
908 if discr
!= nndiscr
{
909 let llptrptr
= GEPi(bcx
, val
, &discrfield
[..]);
910 let llptrty
= val_ty(llptrptr
).element_type();
911 Store(bcx
, C_null(llptrty
), llptrptr
)
917 fn assert_discr_in_range(ity
: IntType
, min
: Disr
, max
: Disr
, discr
: Disr
) {
919 attr
::UnsignedInt(_
) => assert
!(min
<= discr
&& discr
<= max
),
920 attr
::SignedInt(_
) => assert
!(min
as i64 <= discr
as i64 && discr
as i64 <= max
as i64)
924 /// The number of fields in a given case; for use when obtaining this
925 /// information from the type or definition is less convenient.
926 pub fn num_args(r
: &Repr
, discr
: Disr
) -> usize {
929 Univariant(ref st
, dtor
) => {
930 assert_eq
!(discr
, 0);
931 st
.fields
.len() - (if dtor_active(dtor
) { 1 }
else { 0 }
)
933 General(_
, ref cases
, dtor
) => {
934 cases
[discr
as usize].fields
.len() - 1 - (if dtor_active(dtor
) { 1 }
else { 0 }
)
936 RawNullablePointer { nndiscr, ref nullfields, .. }
=> {
937 if discr
== nndiscr { 1 }
else { nullfields.len() }
939 StructWrappedNullablePointer
{ ref nonnull
, nndiscr
,
940 ref nullfields
, .. } => {
941 if discr
== nndiscr { nonnull.fields.len() }
else { nullfields.len() }
946 /// Access a field, at a point when the value's case is known.
947 pub fn trans_field_ptr
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
<'tcx
>,
948 val
: ValueRef
, discr
: Disr
, ix
: usize) -> ValueRef
{
949 // Note: if this ever needs to generate conditionals (e.g., if we
950 // decide to do some kind of cdr-coding-like non-unique repr
951 // someday), it will need to return a possibly-new bcx as well.
954 bcx
.ccx().sess().bug("element access in C-like enum")
956 Univariant(ref st
, _dtor
) => {
957 assert_eq
!(discr
, 0);
958 struct_field_ptr(bcx
, st
, val
, ix
, false)
960 General(_
, ref cases
, _
) => {
961 struct_field_ptr(bcx
, &cases
[discr
as usize], val
, ix
+ 1, true)
963 RawNullablePointer { nndiscr, ref nullfields, .. }
|
964 StructWrappedNullablePointer { nndiscr, ref nullfields, .. }
if discr
!= nndiscr
=> {
965 // The unit-like case might have a nonzero number of unit-like fields.
966 // (e.d., Result of Either with (), as one side.)
967 let ty
= type_of
::type_of(bcx
.ccx(), nullfields
[ix
]);
968 assert_eq
!(machine
::llsize_of_alloc(bcx
.ccx(), ty
), 0);
969 // The contents of memory at this pointer can't matter, but use
970 // the value that's "reasonable" in case of pointer comparison.
971 PointerCast(bcx
, val
, ty
.ptr_to())
973 RawNullablePointer { nndiscr, nnty, .. }
=> {
975 assert_eq
!(discr
, nndiscr
);
976 let ty
= type_of
::type_of(bcx
.ccx(), nnty
);
977 PointerCast(bcx
, val
, ty
.ptr_to())
979 StructWrappedNullablePointer { ref nonnull, nndiscr, .. }
=> {
980 assert_eq
!(discr
, nndiscr
);
981 struct_field_ptr(bcx
, nonnull
, val
, ix
, false)
986 pub fn struct_field_ptr
<'blk
, 'tcx
>(bcx
: Block
<'blk
, 'tcx
>, st
: &Struct
<'tcx
>, val
: ValueRef
,
987 ix
: usize, needs_cast
: bool
) -> ValueRef
{
988 let val
= if needs_cast
{
990 let fields
= st
.fields
.iter().map(|&ty
| type_of
::type_of(ccx
, ty
)).collect
::<Vec
<_
>>();
991 let real_ty
= Type
::struct_(ccx
, &fields
[..], st
.packed
);
992 PointerCast(bcx
, val
, real_ty
.ptr_to())
997 GEPi(bcx
, val
, &[0, ix
])
1000 pub fn fold_variants
<'blk
, 'tcx
, F
>(bcx
: Block
<'blk
, 'tcx
>,
1004 -> Block
<'blk
, 'tcx
> where
1005 F
: FnMut(Block
<'blk
, 'tcx
>, &Struct
<'tcx
>, ValueRef
) -> Block
<'blk
, 'tcx
>,
1009 Univariant(ref st
, _
) => {
1012 General(ity
, ref cases
, _
) => {
1013 let ccx
= bcx
.ccx();
1014 let unr_cx
= fcx
.new_temp_block("enum-variant-iter-unr");
1015 Unreachable(unr_cx
);
1017 let discr_val
= trans_get_discr(bcx
, r
, value
, None
);
1018 let llswitch
= Switch(bcx
, discr_val
, unr_cx
.llbb
, cases
.len());
1019 let bcx_next
= fcx
.new_temp_block("enum-variant-iter-next");
1021 for (discr
, case
) in cases
.iter().enumerate() {
1022 let mut variant_cx
= fcx
.new_temp_block(
1023 &format
!("enum-variant-iter-{}", &discr
.to_string())
1025 let rhs_val
= C_integral(ll_inttype(ccx
, ity
), discr
as u64, true);
1026 AddCase(llswitch
, rhs_val
, variant_cx
.llbb
);
1028 let fields
= case
.fields
.iter().map(|&ty
|
1029 type_of
::type_of(bcx
.ccx(), ty
)).collect
::<Vec
<_
>>();
1030 let real_ty
= Type
::struct_(ccx
, &fields
[..], case
.packed
);
1031 let variant_value
= PointerCast(variant_cx
, value
, real_ty
.ptr_to());
1033 variant_cx
= f(variant_cx
, case
, variant_value
);
1034 Br(variant_cx
, bcx_next
.llbb
, DebugLoc
::None
);
1043 /// Access the struct drop flag, if present.
1044 pub fn trans_drop_flag_ptr
<'blk
, 'tcx
>(mut bcx
: Block
<'blk
, 'tcx
>, r
: &Repr
<'tcx
>, val
: ValueRef
)
1045 -> datum
::DatumBlock
<'blk
, 'tcx
, datum
::Expr
>
1047 let tcx
= bcx
.tcx();
1048 let ptr_ty
= ty
::mk_imm_ptr(bcx
.tcx(), tcx
.dtor_type());
1050 Univariant(ref st
, dtor
) if dtor_active(dtor
) => {
1051 let flag_ptr
= GEPi(bcx
, val
, &[0, st
.fields
.len() - 1]);
1052 datum
::immediate_rvalue_bcx(bcx
, flag_ptr
, ptr_ty
).to_expr_datumblock()
1054 General(_
, _
, dtor
) if dtor_active(dtor
) => {
1056 let custom_cleanup_scope
= fcx
.push_custom_cleanup_scope();
1057 let scratch
= unpack_datum
!(bcx
, datum
::lvalue_scratch_datum(
1058 bcx
, tcx
.dtor_type(), "drop_flag",
1059 cleanup
::CustomScope(custom_cleanup_scope
), (), |_
, bcx
, _
| bcx
1061 bcx
= fold_variants(bcx
, r
, val
, |variant_cx
, st
, value
| {
1062 let ptr
= struct_field_ptr(variant_cx
, st
, value
, (st
.fields
.len() - 1), false);
1063 datum
::Datum
::new(ptr
, ptr_ty
, datum
::Rvalue
::new(datum
::ByRef
))
1064 .store_to(variant_cx
, scratch
.val
)
1066 let expr_datum
= scratch
.to_expr_datum();
1067 fcx
.pop_custom_cleanup_scope(custom_cleanup_scope
);
1068 datum
::DatumBlock
::new(bcx
, expr_datum
)
1070 _
=> bcx
.ccx().sess().bug("tried to get drop flag of non-droppable type")
1074 /// Construct a constant value, suitable for initializing a
1075 /// GlobalVariable, given a case and constant values for its fields.
1076 /// Note that this may have a different LLVM type (and different
1077 /// alignment!) from the representation's `type_of`, so it needs a
1078 /// pointer cast before use.
1080 /// The LLVM type system does not directly support unions, and only
1081 /// pointers can be bitcast, so a constant (and, by extension, the
1082 /// GlobalVariable initialized by it) will have a type that can vary
1083 /// depending on which case of an enum it is.
1085 /// To understand the alignment situation, consider `enum E { V64(u64),
1086 /// V32(u32, u32) }` on Windows. The type has 8-byte alignment to
1087 /// accommodate the u64, but `V32(x, y)` would have LLVM type `{i32,
1088 /// i32, i32}`, which is 4-byte aligned.
1090 /// Currently the returned value has the same size as the type, but
1091 /// this could be changed in the future to avoid allocating unnecessary
1092 /// space after values of shorter-than-maximum cases.
1093 pub fn trans_const
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>, r
: &Repr
<'tcx
>, discr
: Disr
,
1094 vals
: &[ValueRef
]) -> ValueRef
{
1096 CEnum(ity
, min
, max
) => {
1097 assert_eq
!(vals
.len(), 0);
1098 assert_discr_in_range(ity
, min
, max
, discr
);
1099 C_integral(ll_inttype(ccx
, ity
), discr
as u64, true)
1101 General(ity
, ref cases
, _
) => {
1102 let case
= &cases
[discr
as usize];
1103 let (max_sz
, _
) = union_size_and_align(&cases
[..]);
1104 let lldiscr
= C_integral(ll_inttype(ccx
, ity
), discr
as u64, true);
1105 let mut f
= vec
![lldiscr
];
1107 let mut contents
= build_const_struct(ccx
, case
, &f
[..]);
1108 contents
.push_all(&[padding(ccx
, max_sz
- case
.size
)]);
1109 C_struct(ccx
, &contents
[..], false)
1111 Univariant(ref st
, _dro
) => {
1112 assert
!(discr
== 0);
1113 let contents
= build_const_struct(ccx
, st
, vals
);
1114 C_struct(ccx
, &contents
[..], st
.packed
)
1116 RawNullablePointer { nndiscr, nnty, .. }
=> {
1117 if discr
== nndiscr
{
1118 assert_eq
!(vals
.len(), 1);
1121 C_null(type_of
::sizing_type_of(ccx
, nnty
))
1124 StructWrappedNullablePointer { ref nonnull, nndiscr, .. }
=> {
1125 if discr
== nndiscr
{
1126 C_struct(ccx
, &build_const_struct(ccx
,
1131 let vals
= nonnull
.fields
.iter().map(|&ty
| {
1132 // Always use null even if it's not the `discrfield`th
1133 // field; see #8506.
1134 C_null(type_of
::sizing_type_of(ccx
, ty
))
1135 }).collect
::<Vec
<ValueRef
>>();
1136 C_struct(ccx
, &build_const_struct(ccx
,
1145 /// Compute struct field offsets relative to struct begin.
1146 fn compute_struct_field_offsets
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>,
1147 st
: &Struct
<'tcx
>) -> Vec
<u64> {
1148 let mut offsets
= vec
!();
1151 for &ty
in &st
.fields
{
1152 let llty
= type_of
::sizing_type_of(ccx
, ty
);
1154 let type_align
= type_of
::align_of(ccx
, ty
);
1155 offset
= roundup(offset
, type_align
);
1157 offsets
.push(offset
);
1158 offset
+= machine
::llsize_of_alloc(ccx
, llty
);
1160 assert_eq
!(st
.fields
.len(), offsets
.len());
1164 /// Building structs is a little complicated, because we might need to
1165 /// insert padding if a field's value is less aligned than its type.
1167 /// Continuing the example from `trans_const`, a value of type `(u32,
1168 /// E)` should have the `E` at offset 8, but if that field's
1169 /// initializer is 4-byte aligned then simply translating the tuple as
1170 /// a two-element struct will locate it at offset 4, and accesses to it
1171 /// will read the wrong memory.
1172 fn build_const_struct
<'a
, 'tcx
>(ccx
: &CrateContext
<'a
, 'tcx
>,
1173 st
: &Struct
<'tcx
>, vals
: &[ValueRef
])
1175 assert_eq
!(vals
.len(), st
.fields
.len());
1177 let target_offsets
= compute_struct_field_offsets(ccx
, st
);
1179 // offset of current value
1181 let mut cfields
= Vec
::new();
1182 for (&val
, &target_offset
) in vals
.iter().zip(target_offsets
.iter()) {
1184 let val_align
= machine
::llalign_of_min(ccx
, val_ty(val
));
1185 offset
= roundup(offset
, val_align
);
1187 if offset
!= target_offset
{
1188 cfields
.push(padding(ccx
, target_offset
- offset
));
1189 offset
= target_offset
;
1191 assert
!(!is_undef(val
));
1193 offset
+= machine
::llsize_of_alloc(ccx
, val_ty(val
));
1196 assert
!(st
.sized
&& offset
<= st
.size
);
1197 if offset
!= st
.size
{
1198 cfields
.push(padding(ccx
, st
.size
- offset
));
1204 fn padding(ccx
: &CrateContext
, size
: u64) -> ValueRef
{
1205 C_undef(Type
::array(&Type
::i8(ccx
), size
))
1208 // FIXME this utility routine should be somewhere more general
1210 fn roundup(x
: u64, a
: u32) -> u64 { let a = a as u64; ((x + (a - 1)) / a) * a }
1212 /// Get the discriminant of a constant value.
1213 pub fn const_get_discrim(ccx
: &CrateContext
, r
: &Repr
, val
: ValueRef
) -> Disr
{
1215 CEnum(ity
, _
, _
) => {
1217 attr
::SignedInt(..) => const_to_int(val
) as Disr
,
1218 attr
::UnsignedInt(..) => const_to_uint(val
) as Disr
1221 General(ity
, _
, _
) => {
1223 attr
::SignedInt(..) => const_to_int(const_get_elt(ccx
, val
, &[0])) as Disr
,
1224 attr
::UnsignedInt(..) => const_to_uint(const_get_elt(ccx
, val
, &[0])) as Disr
1227 Univariant(..) => 0,
1228 RawNullablePointer { .. }
| StructWrappedNullablePointer { .. }
=> {
1229 ccx
.sess().bug("const discrim access of non c-like enum")
1234 /// Extract a field of a constant value, as appropriate for its
1237 /// (Not to be confused with `common::const_get_elt`, which operates on
1238 /// raw LLVM-level structs and arrays.)
1239 pub fn const_get_field(ccx
: &CrateContext
, r
: &Repr
, val
: ValueRef
,
1240 _discr
: Disr
, ix
: usize) -> ValueRef
{
1242 CEnum(..) => ccx
.sess().bug("element access in C-like enum const"),
1243 Univariant(..) => const_struct_field(ccx
, val
, ix
),
1244 General(..) => const_struct_field(ccx
, val
, ix
+ 1),
1245 RawNullablePointer { .. }
=> {
1249 StructWrappedNullablePointer{ .. }
=> const_struct_field(ccx
, val
, ix
)
1253 /// Extract field of struct-like const, skipping our alignment padding.
1254 fn const_struct_field(ccx
: &CrateContext
, val
: ValueRef
, ix
: usize) -> ValueRef
{
1255 // Get the ix-th non-undef element of the struct.
1256 let mut real_ix
= 0; // actual position in the struct
1257 let mut ix
= ix
; // logical index relative to real_ix
1261 field
= const_get_elt(ccx
, val
, &[real_ix
]);
1262 if !is_undef(field
) {
1265 real_ix
= real_ix
+ 1;
1271 real_ix
= real_ix
+ 1;