1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use rustc::mir::interpret::ConstEvalErr;
13 use rustc::mir::interpret::{ConstValue, ScalarMaybeUndef};
15 use rustc::ty::layout::{self, Align, LayoutOf, TyLayout};
16 use rustc_data_structures::indexed_vec::Idx;
17 use rustc_data_structures::sync::Lrc;
20 use common::{CodegenCx, C_undef, C_usize};
21 use builder::{Builder, MemFlags};
23 use type_of::LayoutLlvmExt;
27 use super::{FunctionCx, LocalRef};
28 use super::constant::scalar_to_llvm;
29 use super::place::PlaceRef;
31 /// The representation of a Rust value. The enum variant is in fact
32 /// uniquely determined by the value's type, but is kept as a
34 #[derive(Copy, Clone, Debug)]
35 pub enum OperandValue<'ll> {
36 /// A reference to the actual operand. The data is guaranteed
37 /// to be valid for the operand's lifetime.
38 Ref(&'ll Value, Align),
39 /// A single LLVM value.
40 Immediate(&'ll Value),
41 /// A pair of immediate LLVM values. Used by fat pointers too.
42 Pair(&'ll Value, &'ll Value)
45 /// An `OperandRef` is an "SSA" reference to a Rust value, along with
48 /// NOTE: unless you know a value's type exactly, you should not
49 /// generate LLVM opcodes acting on it and instead act via methods,
50 /// to avoid nasty edge cases. In particular, using `Builder::store`
51 /// directly is sure to cause problems -- use `OperandRef::store`
53 #[derive(Copy, Clone)]
54 pub struct OperandRef<'ll, 'tcx> {
56 pub val: OperandValue<'ll>,
58 // The layout of value, based on its Rust type.
59 pub layout: TyLayout<'tcx>,
62 impl fmt::Debug for OperandRef<'ll, 'tcx> {
63 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
64 write!(f, "OperandRef({:?} @ {:?})", self.val, self.layout)
68 impl OperandRef<'ll, 'tcx> {
69 pub fn new_zst(cx: &CodegenCx<'ll, 'tcx>,
70 layout: TyLayout<'tcx>) -> OperandRef<'ll, 'tcx> {
71 assert!(layout.is_zst());
73 val: OperandValue::Immediate(C_undef(layout.immediate_llvm_type(cx))),
78 pub fn from_const(bx: &Builder<'a, 'll, 'tcx>,
79 val: &'tcx ty::Const<'tcx>)
80 -> Result<OperandRef<'ll, 'tcx>, Lrc<ConstEvalErr<'tcx>>> {
81 let layout = bx.cx.layout_of(val.ty);
84 return Ok(OperandRef::new_zst(bx.cx, layout));
87 let val = match val.val {
88 ConstValue::Unevaluated(..) => bug!(),
89 ConstValue::Scalar(x) => {
90 let scalar = match layout.abi {
91 layout::Abi::Scalar(ref x) => x,
92 _ => bug!("from_const: invalid ByVal layout: {:#?}", layout)
94 let llval = scalar_to_llvm(
98 layout.immediate_llvm_type(bx.cx),
100 OperandValue::Immediate(llval)
102 ConstValue::ScalarPair(a, b) => {
103 let (a_scalar, b_scalar) = match layout.abi {
104 layout::Abi::ScalarPair(ref a, ref b) => (a, b),
105 _ => bug!("from_const: invalid ScalarPair layout: {:#?}", layout)
107 let a_llval = scalar_to_llvm(
111 layout.scalar_pair_element_llvm_type(bx.cx, 0, true),
113 let b_layout = layout.scalar_pair_element_llvm_type(bx.cx, 1, true);
114 let b_llval = match b {
115 ScalarMaybeUndef::Scalar(b) => scalar_to_llvm(
121 ScalarMaybeUndef::Undef => C_undef(b_layout),
123 OperandValue::Pair(a_llval, b_llval)
125 ConstValue::ByRef(alloc, offset) => {
126 return Ok(PlaceRef::from_const_alloc(bx, layout, alloc, offset).load(bx));
136 /// Asserts that this operand refers to a scalar and returns
137 /// a reference to its value.
138 pub fn immediate(self) -> &'ll Value {
140 OperandValue::Immediate(s) => s,
141 _ => bug!("not immediate: {:?}", self)
145 pub fn deref(self, cx: &CodegenCx<'ll, 'tcx>) -> PlaceRef<'ll, 'tcx> {
146 let projected_ty = self.layout.ty.builtin_deref(true)
147 .unwrap_or_else(|| bug!("deref of non-pointer {:?}", self)).ty;
148 let (llptr, llextra) = match self.val {
149 OperandValue::Immediate(llptr) => (llptr, None),
150 OperandValue::Pair(llptr, llextra) => (llptr, Some(llextra)),
151 OperandValue::Ref(..) => bug!("Deref of by-Ref operand {:?}", self)
153 let layout = cx.layout_of(projected_ty);
162 /// If this operand is a `Pair`, we return an aggregate with the two values.
163 /// For other cases, see `immediate`.
164 pub fn immediate_or_packed_pair(self, bx: &Builder<'a, 'll, 'tcx>) -> &'ll Value {
165 if let OperandValue::Pair(a, b) = self.val {
166 let llty = self.layout.llvm_type(bx.cx);
167 debug!("Operand::immediate_or_packed_pair: packing {:?} into {:?}",
169 // Reconstruct the immediate aggregate.
170 let mut llpair = C_undef(llty);
171 llpair = bx.insert_value(llpair, base::from_immediate(bx, a), 0);
172 llpair = bx.insert_value(llpair, base::from_immediate(bx, b), 1);
179 /// If the type is a pair, we return a `Pair`, otherwise, an `Immediate`.
180 pub fn from_immediate_or_packed_pair(bx: &Builder<'a, 'll, 'tcx>,
182 layout: TyLayout<'tcx>)
183 -> OperandRef<'ll, 'tcx> {
184 let val = if let layout::Abi::ScalarPair(ref a, ref b) = layout.abi {
185 debug!("Operand::from_immediate_or_packed_pair: unpacking {:?} @ {:?}",
188 // Deconstruct the immediate aggregate.
189 let a_llval = base::to_immediate_scalar(bx, bx.extract_value(llval, 0), a);
190 let b_llval = base::to_immediate_scalar(bx, bx.extract_value(llval, 1), b);
191 OperandValue::Pair(a_llval, b_llval)
193 OperandValue::Immediate(llval)
195 OperandRef { val, layout }
198 pub fn extract_field(&self, bx: &Builder<'a, 'll, 'tcx>, i: usize) -> OperandRef<'ll, 'tcx> {
199 let field = self.layout.field(bx.cx, i);
200 let offset = self.layout.fields.offset(i);
202 let mut val = match (self.val, &self.layout.abi) {
203 // If the field is ZST, it has no data.
204 _ if field.is_zst() => {
205 return OperandRef::new_zst(bx.cx, field);
208 // Newtype of a scalar, scalar pair or vector.
209 (OperandValue::Immediate(_), _) |
210 (OperandValue::Pair(..), _) if field.size == self.layout.size => {
211 assert_eq!(offset.bytes(), 0);
215 // Extract a scalar component from a pair.
216 (OperandValue::Pair(a_llval, b_llval), &layout::Abi::ScalarPair(ref a, ref b)) => {
217 if offset.bytes() == 0 {
218 assert_eq!(field.size, a.value.size(bx.cx));
219 OperandValue::Immediate(a_llval)
221 assert_eq!(offset, a.value.size(bx.cx)
222 .abi_align(b.value.align(bx.cx)));
223 assert_eq!(field.size, b.value.size(bx.cx));
224 OperandValue::Immediate(b_llval)
228 // `#[repr(simd)]` types are also immediate.
229 (OperandValue::Immediate(llval), &layout::Abi::Vector { .. }) => {
230 OperandValue::Immediate(
231 bx.extract_element(llval, C_usize(bx.cx, i as u64)))
234 _ => bug!("OperandRef::extract_field({:?}): not applicable", self)
237 // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
239 OperandValue::Immediate(ref mut llval) => {
240 *llval = bx.bitcast(*llval, field.immediate_llvm_type(bx.cx));
242 OperandValue::Pair(ref mut a, ref mut b) => {
243 *a = bx.bitcast(*a, field.scalar_pair_element_llvm_type(bx.cx, 0, true));
244 *b = bx.bitcast(*b, field.scalar_pair_element_llvm_type(bx.cx, 1, true));
246 OperandValue::Ref(..) => bug!()
256 impl OperandValue<'ll> {
257 pub fn store(self, bx: &Builder<'a, 'll, 'tcx>, dest: PlaceRef<'ll, 'tcx>) {
258 self.store_with_flags(bx, dest, MemFlags::empty());
261 pub fn volatile_store(self, bx: &Builder<'a, 'll, 'tcx>, dest: PlaceRef<'ll, 'tcx>) {
262 self.store_with_flags(bx, dest, MemFlags::VOLATILE);
265 pub fn unaligned_volatile_store(self, bx: &Builder<'a, 'll, 'tcx>, dest: PlaceRef<'ll, 'tcx>) {
266 self.store_with_flags(bx, dest, MemFlags::VOLATILE | MemFlags::UNALIGNED);
269 pub fn nontemporal_store(self, bx: &Builder<'a, 'll, 'tcx>, dest: PlaceRef<'ll, 'tcx>) {
270 self.store_with_flags(bx, dest, MemFlags::NONTEMPORAL);
275 bx: &Builder<'a, 'll, 'tcx>,
276 dest: PlaceRef<'ll, 'tcx>,
279 debug!("OperandRef::store: operand={:?}, dest={:?}", self, dest);
280 // Avoid generating stores of zero-sized values, because the only way to have a zero-sized
281 // value is through `undef`, and store itself is useless.
282 if dest.layout.is_zst() {
286 OperandValue::Ref(r, source_align) => {
287 base::memcpy_ty(bx, dest.llval, r, dest.layout,
288 source_align.min(dest.align), flags)
290 OperandValue::Immediate(s) => {
291 let val = base::from_immediate(bx, s);
292 bx.store_with_flags(val, dest.llval, dest.align, flags);
294 OperandValue::Pair(a, b) => {
295 for (i, &x) in [a, b].iter().enumerate() {
296 let llptr = bx.struct_gep(dest.llval, i as u64);
297 let val = base::from_immediate(bx, x);
298 bx.store_with_flags(val, llptr, dest.align, flags);
305 impl FunctionCx<'a, 'll, 'tcx> {
306 fn maybe_codegen_consume_direct(&mut self,
307 bx: &Builder<'a, 'll, 'tcx>,
308 place: &mir::Place<'tcx>)
309 -> Option<OperandRef<'ll, 'tcx>>
311 debug!("maybe_codegen_consume_direct(place={:?})", place);
313 // watch out for locals that do not have an
314 // alloca; they are handled somewhat differently
315 if let mir::Place::Local(index) = *place {
316 match self.locals[index] {
317 LocalRef::Operand(Some(o)) => {
320 LocalRef::Operand(None) => {
321 bug!("use of {:?} before def", place);
323 LocalRef::Place(..) => {
329 // Moves out of scalar and scalar pair fields are trivial.
330 if let &mir::Place::Projection(ref proj) = place {
331 if let Some(o) = self.maybe_codegen_consume_direct(bx, &proj.base) {
333 mir::ProjectionElem::Field(ref f, _) => {
334 return Some(o.extract_field(bx, f.index()));
336 mir::ProjectionElem::Index(_) |
337 mir::ProjectionElem::ConstantIndex { .. } => {
338 // ZSTs don't require any actual memory access.
339 // FIXME(eddyb) deduplicate this with the identical
340 // checks in `codegen_consume` and `extract_field`.
341 let elem = o.layout.field(bx.cx, 0);
343 return Some(OperandRef::new_zst(bx.cx, elem));
354 pub fn codegen_consume(&mut self,
355 bx: &Builder<'a, 'll, 'tcx>,
356 place: &mir::Place<'tcx>)
357 -> OperandRef<'ll, 'tcx>
359 debug!("codegen_consume(place={:?})", place);
361 let ty = self.monomorphized_place_ty(place);
362 let layout = bx.cx.layout_of(ty);
364 // ZSTs don't require any actual memory access.
366 return OperandRef::new_zst(bx.cx, layout);
369 if let Some(o) = self.maybe_codegen_consume_direct(bx, place) {
373 // for most places, to consume them we just load them
374 // out from their home
375 self.codegen_place(bx, place).load(bx)
378 pub fn codegen_operand(&mut self,
379 bx: &Builder<'a, 'll, 'tcx>,
380 operand: &mir::Operand<'tcx>)
381 -> OperandRef<'ll, 'tcx>
383 debug!("codegen_operand(operand={:?})", operand);
386 mir::Operand::Copy(ref place) |
387 mir::Operand::Move(ref place) => {
388 self.codegen_consume(bx, place)
391 mir::Operand::Constant(ref constant) => {
392 let ty = self.monomorphize(&constant.ty);
393 self.eval_mir_constant(bx, constant)
394 .and_then(|c| OperandRef::from_const(bx, c))
395 .unwrap_or_else(|err| {
397 bx.tcx().at(constant.span),
398 "could not evaluate constant operand",
400 // Allow RalfJ to sleep soundly knowing that even refactorings that remove
401 // the above error (or silence it under some conditions) will not cause UB
402 let fnname = bx.cx.get_intrinsic(&("llvm.trap"));
403 bx.call(fnname, &[], None);
404 // We've errored, so we don't have to produce working code.
405 let layout = bx.cx.layout_of(ty);
407 C_undef(layout.llvm_type(bx.cx).ptr_to()),