1 use super::place::PlaceRef;
2 use super::{FunctionCx, LocalRef};
10 use rustc_middle::mir::interpret::{ConstValue, Pointer, Scalar};
11 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
12 use rustc_middle::ty::Ty;
13 use rustc_target::abi::{Abi, Align, Size};
17 /// The representation of a Rust value. The enum variant is in fact
18 /// uniquely determined by the value's type, but is kept as a
20 #[derive(Copy, Clone, Debug)]
21 pub enum OperandValue<V> {
22 /// A reference to the actual operand. The data is guaranteed
23 /// to be valid for the operand's lifetime.
24 /// The second value, if any, is the extra data (vtable or length)
25 /// which indicates that it refers to an unsized rvalue.
26 Ref(V, Option<V>, Align),
27 /// A single LLVM value.
29 /// A pair of immediate LLVM values. Used by fat pointers too.
33 /// An `OperandRef` is an "SSA" reference to a Rust value, along with
36 /// NOTE: unless you know a value's type exactly, you should not
37 /// generate LLVM opcodes acting on it and instead act via methods,
38 /// to avoid nasty edge cases. In particular, using `Builder::store`
39 /// directly is sure to cause problems -- use `OperandRef::store`
41 #[derive(Copy, Clone)]
42 pub struct OperandRef<'tcx, V> {
44 pub val: OperandValue<V>,
46 // The layout of value, based on its Rust type.
47 pub layout: TyAndLayout<'tcx>,
50 impl<V: CodegenObject> fmt::Debug for OperandRef<'_, V> {
51 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
52 write!(f, "OperandRef({:?} @ {:?})", self.val, self.layout)
56 impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
57 pub fn new_zst<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
59 layout: TyAndLayout<'tcx>,
60 ) -> OperandRef<'tcx, V> {
61 assert!(layout.is_zst());
63 val: OperandValue::Immediate(bx.const_undef(bx.immediate_backend_type(layout))),
68 pub fn from_const<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
70 val: ConstValue<'tcx>,
73 let layout = bx.layout_of(ty);
76 ConstValue::Scalar(x) => {
77 let Abi::Scalar(scalar) = layout.abi else {
78 bug!("from_const: invalid ByVal layout: {:#?}", layout);
80 let llval = bx.scalar_to_backend(x, scalar, bx.immediate_backend_type(layout));
81 OperandValue::Immediate(llval)
83 ConstValue::ZeroSized => return OperandRef::new_zst(bx, layout),
84 ConstValue::Slice { data, start, end } => {
85 let Abi::ScalarPair(a_scalar, _) = layout.abi else {
86 bug!("from_const: invalid ScalarPair layout: {:#?}", layout);
88 let a = Scalar::from_pointer(
89 Pointer::new(bx.tcx().create_memory_alloc(data), Size::from_bytes(start)),
92 let a_llval = bx.scalar_to_backend(
95 bx.scalar_pair_element_backend_type(layout, 0, true),
97 let b_llval = bx.const_usize((end - start) as u64);
98 OperandValue::Pair(a_llval, b_llval)
100 ConstValue::ByRef { alloc, offset } => {
101 return bx.load_operand(bx.from_const_alloc(layout, alloc, offset));
105 OperandRef { val, layout }
108 /// Asserts that this operand refers to a scalar and returns
109 /// a reference to its value.
110 pub fn immediate(self) -> V {
112 OperandValue::Immediate(s) => s,
113 _ => bug!("not immediate: {:?}", self),
117 pub fn deref<Cx: LayoutTypeMethods<'tcx>>(self, cx: &Cx) -> PlaceRef<'tcx, V> {
118 if self.layout.ty.is_box() {
119 bug!("dereferencing {:?} in codegen", self.layout.ty);
122 let projected_ty = self
126 .unwrap_or_else(|| bug!("deref of non-pointer {:?}", self))
129 let (llptr, llextra) = match self.val {
130 OperandValue::Immediate(llptr) => (llptr, None),
131 OperandValue::Pair(llptr, llextra) => (llptr, Some(llextra)),
132 OperandValue::Ref(..) => bug!("Deref of by-Ref operand {:?}", self),
134 let layout = cx.layout_of(projected_ty);
135 PlaceRef { llval: llptr, llextra, layout, align: layout.align.abi }
138 /// If this operand is a `Pair`, we return an aggregate with the two values.
139 /// For other cases, see `immediate`.
140 pub fn immediate_or_packed_pair<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
144 if let OperandValue::Pair(a, b) = self.val {
145 let llty = bx.cx().backend_type(self.layout);
146 debug!("Operand::immediate_or_packed_pair: packing {:?} into {:?}", self, llty);
147 // Reconstruct the immediate aggregate.
148 let mut llpair = bx.cx().const_undef(llty);
149 let imm_a = bx.from_immediate(a);
150 let imm_b = bx.from_immediate(b);
151 llpair = bx.insert_value(llpair, imm_a, 0);
152 llpair = bx.insert_value(llpair, imm_b, 1);
159 /// If the type is a pair, we return a `Pair`, otherwise, an `Immediate`.
160 pub fn from_immediate_or_packed_pair<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
163 layout: TyAndLayout<'tcx>,
165 let val = if let Abi::ScalarPair(a, b) = layout.abi {
166 debug!("Operand::from_immediate_or_packed_pair: unpacking {:?} @ {:?}", llval, layout);
168 // Deconstruct the immediate aggregate.
169 let a_llval = bx.extract_value(llval, 0);
170 let a_llval = bx.to_immediate_scalar(a_llval, a);
171 let b_llval = bx.extract_value(llval, 1);
172 let b_llval = bx.to_immediate_scalar(b_llval, b);
173 OperandValue::Pair(a_llval, b_llval)
175 OperandValue::Immediate(llval)
177 OperandRef { val, layout }
180 pub fn extract_field<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
185 let field = self.layout.field(bx.cx(), i);
186 let offset = self.layout.fields.offset(i);
188 let mut val = match (self.val, self.layout.abi) {
189 // If the field is ZST, it has no data.
190 _ if field.is_zst() => {
191 return OperandRef::new_zst(bx, field);
194 // Newtype of a scalar, scalar pair or vector.
195 (OperandValue::Immediate(_) | OperandValue::Pair(..), _)
196 if field.size == self.layout.size =>
198 assert_eq!(offset.bytes(), 0);
202 // Extract a scalar component from a pair.
203 (OperandValue::Pair(a_llval, b_llval), Abi::ScalarPair(a, b)) => {
204 if offset.bytes() == 0 {
205 assert_eq!(field.size, a.size(bx.cx()));
206 OperandValue::Immediate(a_llval)
208 assert_eq!(offset, a.size(bx.cx()).align_to(b.align(bx.cx()).abi));
209 assert_eq!(field.size, b.size(bx.cx()));
210 OperandValue::Immediate(b_llval)
214 // `#[repr(simd)]` types are also immediate.
215 (OperandValue::Immediate(llval), Abi::Vector { .. }) => {
216 OperandValue::Immediate(bx.extract_element(llval, bx.cx().const_usize(i as u64)))
219 _ => bug!("OperandRef::extract_field({:?}): not applicable", self),
222 match (&mut val, field.abi) {
223 (OperandValue::Immediate(llval), _) => {
224 // Bools in union fields needs to be truncated.
225 *llval = bx.to_immediate(*llval, field);
226 // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
227 *llval = bx.bitcast(*llval, bx.cx().immediate_backend_type(field));
229 (OperandValue::Pair(a, b), Abi::ScalarPair(a_abi, b_abi)) => {
230 // Bools in union fields needs to be truncated.
231 *a = bx.to_immediate_scalar(*a, a_abi);
232 *b = bx.to_immediate_scalar(*b, b_abi);
233 // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
234 *a = bx.bitcast(*a, bx.cx().scalar_pair_element_backend_type(field, 0, true));
235 *b = bx.bitcast(*b, bx.cx().scalar_pair_element_backend_type(field, 1, true));
237 (OperandValue::Pair(..), _) => bug!(),
238 (OperandValue::Ref(..), _) => bug!(),
241 OperandRef { val, layout: field }
245 impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
246 pub fn store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
249 dest: PlaceRef<'tcx, V>,
251 self.store_with_flags(bx, dest, MemFlags::empty());
254 pub fn volatile_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
257 dest: PlaceRef<'tcx, V>,
259 self.store_with_flags(bx, dest, MemFlags::VOLATILE);
262 pub fn unaligned_volatile_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
265 dest: PlaceRef<'tcx, V>,
267 self.store_with_flags(bx, dest, MemFlags::VOLATILE | MemFlags::UNALIGNED);
270 pub fn nontemporal_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
273 dest: PlaceRef<'tcx, V>,
275 self.store_with_flags(bx, dest, MemFlags::NONTEMPORAL);
278 fn store_with_flags<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
281 dest: PlaceRef<'tcx, V>,
284 debug!("OperandRef::store: operand={:?}, dest={:?}", self, dest);
285 // Avoid generating stores of zero-sized values, because the only way to have a zero-sized
286 // value is through `undef`, and store itself is useless.
287 if dest.layout.is_zst() {
291 OperandValue::Ref(r, None, source_align) => {
292 if flags.contains(MemFlags::NONTEMPORAL) {
293 // HACK(nox): This is inefficient but there is no nontemporal memcpy.
294 let ty = bx.backend_type(dest.layout);
295 let ptr = bx.pointercast(r, bx.type_ptr_to(ty));
296 let val = bx.load(ty, ptr, source_align);
297 bx.store_with_flags(val, dest.llval, dest.align, flags);
300 base::memcpy_ty(bx, dest.llval, dest.align, r, source_align, dest.layout, flags)
302 OperandValue::Ref(_, Some(_), _) => {
303 bug!("cannot directly store unsized values");
305 OperandValue::Immediate(s) => {
306 let val = bx.from_immediate(s);
307 bx.store_with_flags(val, dest.llval, dest.align, flags);
309 OperandValue::Pair(a, b) => {
310 let Abi::ScalarPair(a_scalar, b_scalar) = dest.layout.abi else {
311 bug!("store_with_flags: invalid ScalarPair layout: {:#?}", dest.layout);
313 let ty = bx.backend_type(dest.layout);
314 let b_offset = a_scalar.size(bx).align_to(b_scalar.align(bx).abi);
316 let llptr = bx.struct_gep(ty, dest.llval, 0);
317 let val = bx.from_immediate(a);
318 let align = dest.align;
319 bx.store_with_flags(val, llptr, align, flags);
321 let llptr = bx.struct_gep(ty, dest.llval, 1);
322 let val = bx.from_immediate(b);
323 let align = dest.align.restrict_for_offset(b_offset);
324 bx.store_with_flags(val, llptr, align, flags);
329 pub fn store_unsized<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
332 indirect_dest: PlaceRef<'tcx, V>,
334 debug!("OperandRef::store_unsized: operand={:?}, indirect_dest={:?}", self, indirect_dest);
335 let flags = MemFlags::empty();
337 // `indirect_dest` must have `*mut T` type. We extract `T` out of it.
338 let unsized_ty = indirect_dest
342 .unwrap_or_else(|| bug!("indirect_dest has non-pointer type: {:?}", indirect_dest))
345 let OperandValue::Ref(llptr, Some(llextra), _) = self else {
346 bug!("store_unsized called with a sized value")
349 // FIXME: choose an appropriate alignment, or use dynamic align somehow
350 let max_align = Align::from_bits(128).unwrap();
351 let min_align = Align::from_bits(8).unwrap();
353 // Allocate an appropriate region on the stack, and copy the value into it
354 let (llsize, _) = glue::size_and_align_of_dst(bx, unsized_ty, Some(llextra));
355 let lldst = bx.array_alloca(bx.cx().type_i8(), llsize, max_align);
356 bx.memcpy(lldst, max_align, llptr, min_align, llsize, flags);
358 // Store the allocated region and the extra to the indirect place.
359 let indirect_operand = OperandValue::Pair(lldst, llextra);
360 indirect_operand.store(bx, indirect_dest);
364 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
365 fn maybe_codegen_consume_direct(
368 place_ref: mir::PlaceRef<'tcx>,
369 ) -> Option<OperandRef<'tcx, Bx::Value>> {
370 debug!("maybe_codegen_consume_direct(place_ref={:?})", place_ref);
372 match self.locals[place_ref.local] {
373 LocalRef::Operand(Some(mut o)) => {
374 // Moves out of scalar and scalar pair fields are trivial.
375 for elem in place_ref.projection.iter() {
377 mir::ProjectionElem::Field(ref f, _) => {
378 o = o.extract_field(bx, f.index());
380 mir::ProjectionElem::Index(_)
381 | mir::ProjectionElem::ConstantIndex { .. } => {
382 // ZSTs don't require any actual memory access.
383 // FIXME(eddyb) deduplicate this with the identical
384 // checks in `codegen_consume` and `extract_field`.
385 let elem = o.layout.field(bx.cx(), 0);
387 o = OperandRef::new_zst(bx, elem);
398 LocalRef::Operand(None) => {
399 bug!("use of {:?} before def", place_ref);
401 LocalRef::Place(..) | LocalRef::UnsizedPlace(..) => {
402 // watch out for locals that do not have an
403 // alloca; they are handled somewhat differently
409 pub fn codegen_consume(
412 place_ref: mir::PlaceRef<'tcx>,
413 ) -> OperandRef<'tcx, Bx::Value> {
414 debug!("codegen_consume(place_ref={:?})", place_ref);
416 let ty = self.monomorphized_place_ty(place_ref);
417 let layout = bx.cx().layout_of(ty);
419 // ZSTs don't require any actual memory access.
421 return OperandRef::new_zst(bx, layout);
424 if let Some(o) = self.maybe_codegen_consume_direct(bx, place_ref) {
428 // for most places, to consume them we just load them
429 // out from their home
430 let place = self.codegen_place(bx, place_ref);
431 bx.load_operand(place)
434 pub fn codegen_operand(
437 operand: &mir::Operand<'tcx>,
438 ) -> OperandRef<'tcx, Bx::Value> {
439 debug!("codegen_operand(operand={:?})", operand);
442 mir::Operand::Copy(ref place) | mir::Operand::Move(ref place) => {
443 self.codegen_consume(bx, place.as_ref())
446 mir::Operand::Constant(ref constant) => {
447 // This cannot fail because we checked all required_consts in advance.
448 self.eval_mir_constant_to_operand(bx, constant).unwrap_or_else(|_err| {
449 span_bug!(constant.span, "erroneous constant not captured by required_consts")