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.
12 use rustc::ty::{self, layout, Ty, TypeFoldable};
14 use rustc::mir::tcx::LvalueTy;
15 use rustc_data_structures::indexed_vec::Idx;
18 use common::{self, CrateContext, C_uint};
29 use super::{MirContext, LocalRef};
30 use super::operand::OperandValue;
32 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
38 impl ops::BitOr for Alignment {
41 fn bitor(self, rhs: Self) -> Self {
43 (Alignment::Packed, _) => Alignment::Packed,
44 (Alignment::AbiAligned, a) => a,
50 pub fn from_packed(packed: bool) -> Self {
58 pub fn to_align(self) -> Option<u32> {
60 Alignment::Packed => Some(1),
61 Alignment::AbiAligned => None,
65 pub fn min_with(self, align: u32) -> Option<u32> {
67 Alignment::Packed => Some(1),
68 Alignment::AbiAligned => Some(align),
73 #[derive(Copy, Clone, Debug)]
74 pub struct LvalueRef<'tcx> {
75 /// Pointer to the contents of the lvalue
78 /// This lvalue's extra data if it is unsized, or null
79 pub llextra: ValueRef,
81 /// Monomorphized type of this lvalue, including variant information
82 pub ty: LvalueTy<'tcx>,
84 /// Whether this lvalue is known to be aligned according to its layout
85 pub alignment: Alignment,
88 impl<'a, 'tcx> LvalueRef<'tcx> {
89 pub fn new_sized(llval: ValueRef, lvalue_ty: LvalueTy<'tcx>,
90 alignment: Alignment) -> LvalueRef<'tcx> {
91 LvalueRef { llval: llval, llextra: ptr::null_mut(), ty: lvalue_ty, alignment: alignment }
94 pub fn new_sized_ty(llval: ValueRef, ty: Ty<'tcx>, alignment: Alignment) -> LvalueRef<'tcx> {
95 LvalueRef::new_sized(llval, LvalueTy::from_ty(ty), alignment)
98 pub fn new_unsized_ty(llval: ValueRef, llextra: ValueRef, ty: Ty<'tcx>, alignment: Alignment)
103 ty: LvalueTy::from_ty(ty),
104 alignment: alignment,
108 pub fn alloca(bcx: &Builder<'a, 'tcx>, ty: Ty<'tcx>, name: &str) -> LvalueRef<'tcx> {
109 debug!("alloca({:?}: {:?})", name, ty);
110 let tmp = bcx.alloca(type_of::type_of(bcx.ccx, ty), name);
111 assert!(!ty.has_param_types());
112 Self::new_sized_ty(tmp, ty, Alignment::AbiAligned)
115 pub fn len(&self, ccx: &CrateContext<'a, 'tcx>) -> ValueRef {
116 let ty = self.ty.to_ty(ccx.tcx());
118 ty::TyArray(_, n) => common::C_uint(ccx, n),
119 ty::TySlice(_) | ty::TyStr => {
120 assert!(self.llextra != ptr::null_mut());
123 _ => bug!("unexpected type `{}` in LvalueRef::len", ty)
127 pub fn has_extra(&self) -> bool {
128 !self.llextra.is_null()
133 bcx: &Builder<'a, 'tcx>,
135 fields: &Vec<Ty<'tcx>>,
138 ) -> (ValueRef, Alignment) {
139 let fty = fields[ix];
142 let alignment = self.alignment | Alignment::from_packed(st.packed);
144 let ptr_val = if needs_cast {
145 let fields = st.field_index_by_increasing_offset().map(|i| {
146 type_of::in_memory_type_of(ccx, fields[i])
147 }).collect::<Vec<_>>();
148 let real_ty = Type::struct_(ccx, &fields[..], st.packed);
149 bcx.pointercast(self.llval, real_ty.ptr_to())
154 // Simple case - we can just GEP the field
155 // * First field - Always aligned properly
156 // * Packed struct - There is no alignment padding
157 // * Field is sized - pointer is properly aligned already
158 if st.offsets[ix] == layout::Size::from_bytes(0) || st.packed ||
159 bcx.ccx.shared().type_is_sized(fty) {
160 return (bcx.struct_gep(ptr_val, st.memory_index[ix] as usize), alignment);
163 // If the type of the last field is [T] or str, then we don't need to do
166 ty::TySlice(..) | ty::TyStr => {
167 return (bcx.struct_gep(ptr_val, st.memory_index[ix] as usize), alignment);
172 // There's no metadata available, log the case and just do the GEP.
173 if !self.has_extra() {
174 debug!("Unsized field `{}`, of `{:?}` has no metadata for adjustment",
176 return (bcx.struct_gep(ptr_val, ix), alignment);
179 // We need to get the pointer manually now.
180 // We do this by casting to a *i8, then offsetting it by the appropriate amount.
181 // We do this instead of, say, simply adjusting the pointer from the result of a GEP
182 // because the field may have an arbitrary alignment in the LLVM representation
186 // struct Foo<T: ?Sized> {
191 // The type Foo<Foo<Trait>> is represented in LLVM as { u16, { u16, u8 }}, meaning that
192 // the `y` field has 16-bit alignment.
194 let meta = self.llextra;
197 let offset = st.offsets[ix].bytes();
198 let unaligned_offset = C_uint(bcx.ccx, offset);
200 // Get the alignment of the field
201 let (_, align) = glue::size_and_align_of_dst(bcx, fty, meta);
203 // Bump the unaligned offset up to the appropriate alignment using the
204 // following expression:
206 // (unaligned offset + (align - 1)) & -align
209 let align_sub_1 = bcx.sub(align, C_uint(bcx.ccx, 1u64));
210 let offset = bcx.and(bcx.add(unaligned_offset, align_sub_1),
213 debug!("struct_field_ptr: DST field offset: {:?}", Value(offset));
215 // Cast and adjust pointer
216 let byte_ptr = bcx.pointercast(ptr_val, Type::i8p(bcx.ccx));
217 let byte_ptr = bcx.gep(byte_ptr, &[offset]);
219 // Finally, cast back to the type expected
220 let ll_fty = type_of::in_memory_type_of(bcx.ccx, fty);
221 debug!("struct_field_ptr: Field type is {:?}", ll_fty);
222 (bcx.pointercast(byte_ptr, ll_fty.ptr_to()), alignment)
225 /// Access a field, at a point when the value's case is known.
226 pub fn trans_field_ptr(self, bcx: &Builder<'a, 'tcx>, ix: usize) -> (ValueRef, Alignment) {
227 let discr = match self.ty {
228 LvalueTy::Ty { .. } => 0,
229 LvalueTy::Downcast { variant_index, .. } => variant_index,
231 let t = self.ty.to_ty(bcx.tcx());
232 let l = bcx.ccx.layout_of(t);
233 // Note: if this ever needs to generate conditionals (e.g., if we
234 // decide to do some kind of cdr-coding-like non-unique repr
235 // someday), it will need to return a possibly-new bcx as well.
237 layout::Univariant { ref variant, .. } => {
238 assert_eq!(discr, 0);
239 self.struct_field_ptr(bcx, &variant,
240 &adt::compute_fields(bcx.ccx, t, 0, false), ix, false)
242 layout::Vector { count, .. } => {
243 assert_eq!(discr, 0);
244 assert!((ix as u64) < count);
245 (bcx.struct_gep(self.llval, ix), self.alignment)
247 layout::General { discr: d, ref variants, .. } => {
248 let mut fields = adt::compute_fields(bcx.ccx, t, discr, false);
249 fields.insert(0, d.to_ty(&bcx.tcx(), false));
250 self.struct_field_ptr(bcx, &variants[discr], &fields, ix + 1, true)
252 layout::UntaggedUnion { ref variants } => {
253 let fields = adt::compute_fields(bcx.ccx, t, 0, false);
254 let ty = type_of::in_memory_type_of(bcx.ccx, fields[ix]);
255 (bcx.pointercast(self.llval, ty.ptr_to()),
256 self.alignment | Alignment::from_packed(variants.packed))
258 layout::RawNullablePointer { nndiscr, .. } |
259 layout::StructWrappedNullablePointer { nndiscr, .. } if discr as u64 != nndiscr => {
260 let nullfields = adt::compute_fields(bcx.ccx, t, (1-nndiscr) as usize, false);
261 // The unit-like case might have a nonzero number of unit-like fields.
262 // (e.d., Result of Either with (), as one side.)
263 let ty = type_of::type_of(bcx.ccx, nullfields[ix]);
264 assert_eq!(machine::llsize_of_alloc(bcx.ccx, ty), 0);
265 (bcx.pointercast(self.llval, ty.ptr_to()), Alignment::Packed)
267 layout::RawNullablePointer { nndiscr, .. } => {
268 let nnty = adt::compute_fields(bcx.ccx, t, nndiscr as usize, false)[0];
270 assert_eq!(discr as u64, nndiscr);
271 let ty = type_of::type_of(bcx.ccx, nnty);
272 (bcx.pointercast(self.llval, ty.ptr_to()), self.alignment)
274 layout::StructWrappedNullablePointer { ref nonnull, nndiscr, .. } => {
275 assert_eq!(discr as u64, nndiscr);
276 self.struct_field_ptr(bcx, &nonnull,
277 &adt::compute_fields(bcx.ccx, t, discr, false), ix, false)
279 _ => bug!("element access in type without elements: {} represented as {:#?}", t, l)
284 impl<'a, 'tcx> MirContext<'a, 'tcx> {
285 pub fn trans_lvalue(&mut self,
286 bcx: &Builder<'a, 'tcx>,
287 lvalue: &mir::Lvalue<'tcx>)
289 debug!("trans_lvalue(lvalue={:?})", lvalue);
294 if let mir::Lvalue::Local(index) = *lvalue {
295 match self.locals[index] {
296 LocalRef::Lvalue(lvalue) => {
299 LocalRef::Operand(..) => {
300 bug!("using operand local {:?} as lvalue", lvalue);
305 let result = match *lvalue {
306 mir::Lvalue::Local(_) => bug!(), // handled above
307 mir::Lvalue::Static(def_id) => {
308 let const_ty = self.monomorphized_lvalue_ty(lvalue);
309 LvalueRef::new_sized(consts::get_static(ccx, def_id),
310 LvalueTy::from_ty(const_ty),
311 Alignment::AbiAligned)
313 mir::Lvalue::Projection(box mir::Projection {
315 elem: mir::ProjectionElem::Deref
317 // Load the pointer from its location.
318 let ptr = self.trans_consume(bcx, base);
319 let projected_ty = LvalueTy::from_ty(ptr.ty)
320 .projection_ty(tcx, &mir::ProjectionElem::Deref);
321 let projected_ty = self.monomorphize(&projected_ty);
322 let (llptr, llextra) = match ptr.val {
323 OperandValue::Immediate(llptr) => (llptr, ptr::null_mut()),
324 OperandValue::Pair(llptr, llextra) => (llptr, llextra),
325 OperandValue::Ref(..) => bug!("Deref of by-Ref type {:?}", ptr.ty)
331 alignment: Alignment::AbiAligned,
334 mir::Lvalue::Projection(ref projection) => {
335 let tr_base = self.trans_lvalue(bcx, &projection.base);
336 let projected_ty = tr_base.ty.projection_ty(tcx, &projection.elem);
337 let projected_ty = self.monomorphize(&projected_ty);
338 let align = tr_base.alignment;
340 let project_index = |llindex| {
341 let element = if let ty::TySlice(_) = tr_base.ty.to_ty(tcx).sty {
342 // Slices already point to the array element type.
343 bcx.inbounds_gep(tr_base.llval, &[llindex])
345 let zero = common::C_uint(bcx.ccx, 0u64);
346 bcx.inbounds_gep(tr_base.llval, &[zero, llindex])
351 let ((llprojected, align), llextra) = match projection.elem {
352 mir::ProjectionElem::Deref => bug!(),
353 mir::ProjectionElem::Field(ref field, _) => {
354 let llextra = if self.ccx.shared().type_is_sized(projected_ty.to_ty(tcx)) {
359 (tr_base.trans_field_ptr(bcx, field.index()), llextra)
361 mir::ProjectionElem::Index(ref index) => {
362 let index = self.trans_operand(bcx, index);
363 (project_index(self.prepare_index(bcx, index.immediate())), ptr::null_mut())
365 mir::ProjectionElem::ConstantIndex { offset,
368 let lloffset = C_uint(bcx.ccx, offset);
369 (project_index(lloffset), ptr::null_mut())
371 mir::ProjectionElem::ConstantIndex { offset,
374 let lloffset = C_uint(bcx.ccx, offset);
375 let lllen = tr_base.len(bcx.ccx);
376 let llindex = bcx.sub(lllen, lloffset);
377 (project_index(llindex), ptr::null_mut())
379 mir::ProjectionElem::Subslice { from, to } => {
380 let llindex = C_uint(bcx.ccx, from);
381 let (llbase, align) = project_index(llindex);
383 let base_ty = tr_base.ty.to_ty(bcx.tcx());
386 // must cast the lvalue pointer type to the new
387 // array type (*[%_; new_len]).
388 let base_ty = self.monomorphized_lvalue_ty(lvalue);
389 let llbasety = type_of::type_of(bcx.ccx, base_ty).ptr_to();
390 let llbase = bcx.pointercast(llbase, llbasety);
391 ((llbase, align), ptr::null_mut())
394 assert!(tr_base.llextra != ptr::null_mut());
395 let lllen = bcx.sub(tr_base.llextra,
396 C_uint(bcx.ccx, from+to));
397 ((llbase, align), lllen)
399 _ => bug!("unexpected type {:?} in Subslice", base_ty)
402 mir::ProjectionElem::Downcast(..) => {
403 ((tr_base.llval, align), tr_base.llextra)
414 debug!("trans_lvalue(lvalue={:?}) => {:?}", lvalue, result);
418 /// Adjust the bitwidth of an index since LLVM is less forgiving
421 /// nmatsakis: is this still necessary? Not sure.
422 fn prepare_index(&mut self, bcx: &Builder<'a, 'tcx>, llindex: ValueRef) -> ValueRef {
423 let index_size = machine::llbitsize_of_real(bcx.ccx, common::val_ty(llindex));
424 let int_size = machine::llbitsize_of_real(bcx.ccx, bcx.ccx.int_type());
425 if index_size < int_size {
426 bcx.zext(llindex, bcx.ccx.int_type())
427 } else if index_size > int_size {
428 bcx.trunc(llindex, bcx.ccx.int_type())
434 pub fn monomorphized_lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> Ty<'tcx> {
435 let tcx = self.ccx.tcx();
436 let lvalue_ty = lvalue.ty(&self.mir, tcx);
437 self.monomorphize(&lvalue_ty.to_ty(tcx))