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use std::assert_matches::assert_matches;
use std::fmt;
use arrayvec::ArrayVec;
use either::Either;
use rustc_middle::bug;
use rustc_middle::mir::interpret::{alloc_range, Pointer, Scalar};
use rustc_middle::mir::{self, ConstValue};
use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
use rustc_middle::ty::Ty;
use rustc_target::abi::{self, Abi, Align, Size};
use tracing::debug;
use super::place::{PlaceRef, PlaceValue};
use super::{FunctionCx, LocalRef};
use crate::traits::*;
use crate::{size_of_val, MemFlags};
/// The representation of a Rust value. The enum variant is in fact
/// uniquely determined by the value's type, but is kept as a
/// safety check.
#[derive(Copy, Clone, Debug)]
pub enum OperandValue<V> {
/// A reference to the actual operand. The data is guaranteed
/// to be valid for the operand's lifetime.
/// The second value, if any, is the extra data (vtable or length)
/// which indicates that it refers to an unsized rvalue.
///
/// An `OperandValue` *must* be this variant for any type for which
/// [`LayoutTypeMethods::is_backend_ref`] returns `true`.
/// (That basically amounts to "isn't one of the other variants".)
///
/// This holds a [`PlaceValue`] (like a [`PlaceRef`] does) with a pointer
/// to the location holding the value. The type behind that pointer is the
/// one returned by [`LayoutTypeMethods::backend_type`].
Ref(PlaceValue<V>),
/// A single LLVM immediate value.
///
/// An `OperandValue` *must* be this variant for any type for which
/// [`LayoutTypeMethods::is_backend_immediate`] returns `true`.
/// The backend value in this variant must be the *immediate* backend type,
/// as returned by [`LayoutTypeMethods::immediate_backend_type`].
Immediate(V),
/// A pair of immediate LLVM values. Used by fat pointers too.
///
/// An `OperandValue` *must* be this variant for any type for which
/// [`LayoutTypeMethods::is_backend_scalar_pair`] returns `true`.
/// The backend values in this variant must be the *immediate* backend types,
/// as returned by [`LayoutTypeMethods::scalar_pair_element_backend_type`]
/// with `immediate: true`.
Pair(V, V),
/// A value taking no bytes, and which therefore needs no LLVM value at all.
///
/// If you ever need a `V` to pass to something, get a fresh poison value
/// from [`ConstMethods::const_poison`].
///
/// An `OperandValue` *must* be this variant for any type for which
/// `is_zst` on its `Layout` returns `true`. Note however that
/// these values can still require alignment.
ZeroSized,
}
impl<V: CodegenObject> OperandValue<V> {
/// If this is ZeroSized/Immediate/Pair, return an array of the 0/1/2 values.
/// If this is Ref, return the place.
#[inline]
pub fn immediates_or_place(self) -> Either<ArrayVec<V, 2>, PlaceValue<V>> {
match self {
OperandValue::ZeroSized => Either::Left(ArrayVec::new()),
OperandValue::Immediate(a) => Either::Left(ArrayVec::from_iter([a])),
OperandValue::Pair(a, b) => Either::Left([a, b].into()),
OperandValue::Ref(p) => Either::Right(p),
}
}
/// Given an array of 0/1/2 immediate values, return ZeroSized/Immediate/Pair.
#[inline]
pub fn from_immediates(immediates: ArrayVec<V, 2>) -> Self {
let mut it = immediates.into_iter();
let Some(a) = it.next() else {
return OperandValue::ZeroSized;
};
let Some(b) = it.next() else {
return OperandValue::Immediate(a);
};
OperandValue::Pair(a, b)
}
/// Treat this value as a pointer and return the data pointer and
/// optional metadata as backend values.
///
/// If you're making a place, use [`Self::deref`] instead.
pub fn pointer_parts(self) -> (V, Option<V>) {
match self {
OperandValue::Immediate(llptr) => (llptr, None),
OperandValue::Pair(llptr, llextra) => (llptr, Some(llextra)),
_ => bug!("OperandValue cannot be a pointer: {self:?}"),
}
}
/// Treat this value as a pointer and return the place to which it points.
///
/// The pointer immediate doesn't inherently know its alignment,
/// so you need to pass it in. If you want to get it from a type's ABI
/// alignment, then maybe you want [`OperandRef::deref`] instead.
///
/// This is the inverse of [`PlaceValue::address`].
pub fn deref(self, align: Align) -> PlaceValue<V> {
let (llval, llextra) = self.pointer_parts();
PlaceValue { llval, llextra, align }
}
pub(crate) fn is_expected_variant_for_type<'tcx, Cx: LayoutTypeMethods<'tcx>>(
&self,
cx: &Cx,
ty: TyAndLayout<'tcx>,
) -> bool {
match self {
OperandValue::ZeroSized => ty.is_zst(),
OperandValue::Immediate(_) => cx.is_backend_immediate(ty),
OperandValue::Pair(_, _) => cx.is_backend_scalar_pair(ty),
OperandValue::Ref(_) => cx.is_backend_ref(ty),
}
}
}
/// An `OperandRef` is an "SSA" reference to a Rust value, along with
/// its type.
///
/// NOTE: unless you know a value's type exactly, you should not
/// generate LLVM opcodes acting on it and instead act via methods,
/// to avoid nasty edge cases. In particular, using `Builder::store`
/// directly is sure to cause problems -- use `OperandRef::store`
/// instead.
#[derive(Copy, Clone)]
pub struct OperandRef<'tcx, V> {
/// The value.
pub val: OperandValue<V>,
/// The layout of value, based on its Rust type.
pub layout: TyAndLayout<'tcx>,
}
impl<V: CodegenObject> fmt::Debug for OperandRef<'_, V> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "OperandRef({:?} @ {:?})", self.val, self.layout)
}
}
impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
pub fn zero_sized(layout: TyAndLayout<'tcx>) -> OperandRef<'tcx, V> {
assert!(layout.is_zst());
OperandRef { val: OperandValue::ZeroSized, layout }
}
pub fn from_const<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
bx: &mut Bx,
val: mir::ConstValue<'tcx>,
ty: Ty<'tcx>,
) -> Self {
let layout = bx.layout_of(ty);
let val = match val {
ConstValue::Scalar(x) => {
let Abi::Scalar(scalar) = layout.abi else {
bug!("from_const: invalid ByVal layout: {:#?}", layout);
};
let llval = bx.scalar_to_backend(x, scalar, bx.immediate_backend_type(layout));
OperandValue::Immediate(llval)
}
ConstValue::ZeroSized => return OperandRef::zero_sized(layout),
ConstValue::Slice { data, meta } => {
let Abi::ScalarPair(a_scalar, _) = layout.abi else {
bug!("from_const: invalid ScalarPair layout: {:#?}", layout);
};
let a = Scalar::from_pointer(
Pointer::new(bx.tcx().reserve_and_set_memory_alloc(data).into(), Size::ZERO),
&bx.tcx(),
);
let a_llval = bx.scalar_to_backend(
a,
a_scalar,
bx.scalar_pair_element_backend_type(layout, 0, true),
);
let b_llval = bx.const_usize(meta);
OperandValue::Pair(a_llval, b_llval)
}
ConstValue::Indirect { alloc_id, offset } => {
let alloc = bx.tcx().global_alloc(alloc_id).unwrap_memory();
return Self::from_const_alloc(bx, layout, alloc, offset);
}
};
OperandRef { val, layout }
}
fn from_const_alloc<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
bx: &mut Bx,
layout: TyAndLayout<'tcx>,
alloc: rustc_middle::mir::interpret::ConstAllocation<'tcx>,
offset: Size,
) -> Self {
let alloc_align = alloc.inner().align;
assert!(alloc_align >= layout.align.abi);
let read_scalar = |start, size, s: abi::Scalar, ty| {
match alloc.0.read_scalar(
bx,
alloc_range(start, size),
/*read_provenance*/ matches!(s.primitive(), abi::Pointer(_)),
) {
Ok(val) => bx.scalar_to_backend(val, s, ty),
Err(_) => bx.const_poison(ty),
}
};
// It may seem like all types with `Scalar` or `ScalarPair` ABI are fair game at this point.
// However, `MaybeUninit<u64>` is considered a `Scalar` as far as its layout is concerned --
// and yet cannot be represented by an interpreter `Scalar`, since we have to handle the
// case where some of the bytes are initialized and others are not. So, we need an extra
// check that walks over the type of `mplace` to make sure it is truly correct to treat this
// like a `Scalar` (or `ScalarPair`).
match layout.abi {
Abi::Scalar(s @ abi::Scalar::Initialized { .. }) => {
let size = s.size(bx);
assert_eq!(size, layout.size, "abi::Scalar size does not match layout size");
let val = read_scalar(offset, size, s, bx.immediate_backend_type(layout));
OperandRef { val: OperandValue::Immediate(val), layout }
}
Abi::ScalarPair(
a @ abi::Scalar::Initialized { .. },
b @ abi::Scalar::Initialized { .. },
) => {
let (a_size, b_size) = (a.size(bx), b.size(bx));
let b_offset = (offset + a_size).align_to(b.align(bx).abi);
assert!(b_offset.bytes() > 0);
let a_val = read_scalar(
offset,
a_size,
a,
bx.scalar_pair_element_backend_type(layout, 0, true),
);
let b_val = read_scalar(
b_offset,
b_size,
b,
bx.scalar_pair_element_backend_type(layout, 1, true),
);
OperandRef { val: OperandValue::Pair(a_val, b_val), layout }
}
_ if layout.is_zst() => OperandRef::zero_sized(layout),
_ => {
// Neither a scalar nor scalar pair. Load from a place
// FIXME: should we cache `const_data_from_alloc` to avoid repeating this for the
// same `ConstAllocation`?
let init = bx.const_data_from_alloc(alloc);
let base_addr = bx.static_addr_of(init, alloc_align, None);
let llval = bx.const_ptr_byte_offset(base_addr, offset);
bx.load_operand(PlaceRef::new_sized(llval, layout))
}
}
}
/// Asserts that this operand refers to a scalar and returns
/// a reference to its value.
pub fn immediate(self) -> V {
match self.val {
OperandValue::Immediate(s) => s,
_ => bug!("not immediate: {:?}", self),
}
}
/// Asserts that this operand is a pointer (or reference) and returns
/// the place to which it points. (This requires no code to be emitted
/// as we represent places using the pointer to the place.)
///
/// This uses [`Ty::builtin_deref`] to include the type of the place and
/// assumes the place is aligned to the pointee's usual ABI alignment.
///
/// If you don't need the type, see [`OperandValue::pointer_parts`]
/// or [`OperandValue::deref`].
pub fn deref<Cx: LayoutTypeMethods<'tcx>>(self, cx: &Cx) -> PlaceRef<'tcx, V> {
if self.layout.ty.is_box() {
// Derefer should have removed all Box derefs
bug!("dereferencing {:?} in codegen", self.layout.ty);
}
let projected_ty = self
.layout
.ty
.builtin_deref(true)
.unwrap_or_else(|| bug!("deref of non-pointer {:?}", self));
let layout = cx.layout_of(projected_ty);
self.val.deref(layout.align.abi).with_type(layout)
}
/// If this operand is a `Pair`, we return an aggregate with the two values.
/// For other cases, see `immediate`.
pub fn immediate_or_packed_pair<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
self,
bx: &mut Bx,
) -> V {
if let OperandValue::Pair(a, b) = self.val {
let llty = bx.cx().immediate_backend_type(self.layout);
debug!("Operand::immediate_or_packed_pair: packing {:?} into {:?}", self, llty);
// Reconstruct the immediate aggregate.
let mut llpair = bx.cx().const_poison(llty);
llpair = bx.insert_value(llpair, a, 0);
llpair = bx.insert_value(llpair, b, 1);
llpair
} else {
self.immediate()
}
}
/// If the type is a pair, we return a `Pair`, otherwise, an `Immediate`.
pub fn from_immediate_or_packed_pair<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
bx: &mut Bx,
llval: V,
layout: TyAndLayout<'tcx>,
) -> Self {
let val = if let Abi::ScalarPair(..) = layout.abi {
debug!("Operand::from_immediate_or_packed_pair: unpacking {:?} @ {:?}", llval, layout);
// Deconstruct the immediate aggregate.
let a_llval = bx.extract_value(llval, 0);
let b_llval = bx.extract_value(llval, 1);
OperandValue::Pair(a_llval, b_llval)
} else {
OperandValue::Immediate(llval)
};
OperandRef { val, layout }
}
pub fn extract_field<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
&self,
bx: &mut Bx,
i: usize,
) -> Self {
let field = self.layout.field(bx.cx(), i);
let offset = self.layout.fields.offset(i);
let mut val = match (self.val, self.layout.abi) {
// If the field is ZST, it has no data.
_ if field.is_zst() => OperandValue::ZeroSized,
// Newtype of a scalar, scalar pair or vector.
(OperandValue::Immediate(_) | OperandValue::Pair(..), _)
if field.size == self.layout.size =>
{
assert_eq!(offset.bytes(), 0);
self.val
}
// Extract a scalar component from a pair.
(OperandValue::Pair(a_llval, b_llval), Abi::ScalarPair(a, b)) => {
if offset.bytes() == 0 {
assert_eq!(field.size, a.size(bx.cx()));
OperandValue::Immediate(a_llval)
} else {
assert_eq!(offset, a.size(bx.cx()).align_to(b.align(bx.cx()).abi));
assert_eq!(field.size, b.size(bx.cx()));
OperandValue::Immediate(b_llval)
}
}
// `#[repr(simd)]` types are also immediate.
(OperandValue::Immediate(llval), Abi::Vector { .. }) => {
OperandValue::Immediate(bx.extract_element(llval, bx.cx().const_usize(i as u64)))
}
_ => bug!("OperandRef::extract_field({:?}): not applicable", self),
};
match (&mut val, field.abi) {
(OperandValue::ZeroSized, _) => {}
(
OperandValue::Immediate(llval),
Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. },
) => {
// Bools in union fields needs to be truncated.
*llval = bx.to_immediate(*llval, field);
}
(OperandValue::Pair(a, b), Abi::ScalarPair(a_abi, b_abi)) => {
// Bools in union fields needs to be truncated.
*a = bx.to_immediate_scalar(*a, a_abi);
*b = bx.to_immediate_scalar(*b, b_abi);
}
// Newtype vector of array, e.g. #[repr(simd)] struct S([i32; 4]);
(OperandValue::Immediate(llval), Abi::Aggregate { sized: true }) => {
assert_matches!(self.layout.abi, Abi::Vector { .. });
let llfield_ty = bx.cx().backend_type(field);
// Can't bitcast an aggregate, so round trip through memory.
let llptr = bx.alloca(field.size, field.align.abi);
bx.store(*llval, llptr, field.align.abi);
*llval = bx.load(llfield_ty, llptr, field.align.abi);
}
(OperandValue::Immediate(_), Abi::Uninhabited | Abi::Aggregate { sized: false }) => {
bug!()
}
(OperandValue::Pair(..), _) => bug!(),
(OperandValue::Ref(..), _) => bug!(),
}
OperandRef { val, layout: field }
}
}
impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
/// Returns an `OperandValue` that's generally UB to use in any way.
///
/// Depending on the `layout`, returns `ZeroSized` for ZSTs, an `Immediate` or
/// `Pair` containing poison value(s), or a `Ref` containing a poison pointer.
///
/// Supports sized types only.
pub fn poison<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
bx: &mut Bx,
layout: TyAndLayout<'tcx>,
) -> OperandValue<V> {
assert!(layout.is_sized());
if layout.is_zst() {
OperandValue::ZeroSized
} else if bx.cx().is_backend_immediate(layout) {
let ibty = bx.cx().immediate_backend_type(layout);
OperandValue::Immediate(bx.const_poison(ibty))
} else if bx.cx().is_backend_scalar_pair(layout) {
let ibty0 = bx.cx().scalar_pair_element_backend_type(layout, 0, true);
let ibty1 = bx.cx().scalar_pair_element_backend_type(layout, 1, true);
OperandValue::Pair(bx.const_poison(ibty0), bx.const_poison(ibty1))
} else {
let ptr = bx.cx().type_ptr();
OperandValue::Ref(PlaceValue::new_sized(bx.const_poison(ptr), layout.align.abi))
}
}
pub fn store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
self,
bx: &mut Bx,
dest: PlaceRef<'tcx, V>,
) {
self.store_with_flags(bx, dest, MemFlags::empty());
}
pub fn volatile_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
self,
bx: &mut Bx,
dest: PlaceRef<'tcx, V>,
) {
self.store_with_flags(bx, dest, MemFlags::VOLATILE);
}
pub fn unaligned_volatile_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
self,
bx: &mut Bx,
dest: PlaceRef<'tcx, V>,
) {
self.store_with_flags(bx, dest, MemFlags::VOLATILE | MemFlags::UNALIGNED);
}
pub fn nontemporal_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
self,
bx: &mut Bx,
dest: PlaceRef<'tcx, V>,
) {
self.store_with_flags(bx, dest, MemFlags::NONTEMPORAL);
}
pub(crate) fn store_with_flags<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
self,
bx: &mut Bx,
dest: PlaceRef<'tcx, V>,
flags: MemFlags,
) {
debug!("OperandRef::store: operand={:?}, dest={:?}", self, dest);
match self {
OperandValue::ZeroSized => {
// Avoid generating stores of zero-sized values, because the only way to have a zero-sized
// value is through `undef`/`poison`, and the store itself is useless.
}
OperandValue::Ref(val) => {
assert!(dest.layout.is_sized(), "cannot directly store unsized values");
if val.llextra.is_some() {
bug!("cannot directly store unsized values");
}
bx.typed_place_copy_with_flags(dest.val, val, dest.layout, flags);
}
OperandValue::Immediate(s) => {
let val = bx.from_immediate(s);
bx.store_with_flags(val, dest.val.llval, dest.val.align, flags);
}
OperandValue::Pair(a, b) => {
let Abi::ScalarPair(a_scalar, b_scalar) = dest.layout.abi else {
bug!("store_with_flags: invalid ScalarPair layout: {:#?}", dest.layout);
};
let b_offset = a_scalar.size(bx).align_to(b_scalar.align(bx).abi);
let val = bx.from_immediate(a);
let align = dest.val.align;
bx.store_with_flags(val, dest.val.llval, align, flags);
let llptr = bx.inbounds_ptradd(dest.val.llval, bx.const_usize(b_offset.bytes()));
let val = bx.from_immediate(b);
let align = dest.val.align.restrict_for_offset(b_offset);
bx.store_with_flags(val, llptr, align, flags);
}
}
}
pub fn store_unsized<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
self,
bx: &mut Bx,
indirect_dest: PlaceRef<'tcx, V>,
) {
debug!("OperandRef::store_unsized: operand={:?}, indirect_dest={:?}", self, indirect_dest);
// `indirect_dest` must have `*mut T` type. We extract `T` out of it.
let unsized_ty = indirect_dest
.layout
.ty
.builtin_deref(true)
.unwrap_or_else(|| bug!("indirect_dest has non-pointer type: {:?}", indirect_dest));
let OperandValue::Ref(PlaceValue { llval: llptr, llextra: Some(llextra), .. }) = self
else {
bug!("store_unsized called with a sized value (or with an extern type)")
};
// Allocate an appropriate region on the stack, and copy the value into it. Since alloca
// doesn't support dynamic alignment, we allocate an extra align - 1 bytes, and align the
// pointer manually.
let (size, align) = size_of_val::size_and_align_of_dst(bx, unsized_ty, Some(llextra));
let one = bx.const_usize(1);
let align_minus_1 = bx.sub(align, one);
let size_extra = bx.add(size, align_minus_1);
let min_align = Align::ONE;
let alloca = bx.dynamic_alloca(size_extra, min_align);
let address = bx.ptrtoint(alloca, bx.type_isize());
let neg_address = bx.neg(address);
let offset = bx.and(neg_address, align_minus_1);
let dst = bx.inbounds_ptradd(alloca, offset);
bx.memcpy(dst, min_align, llptr, min_align, size, MemFlags::empty());
// Store the allocated region and the extra to the indirect place.
let indirect_operand = OperandValue::Pair(dst, llextra);
indirect_operand.store(bx, indirect_dest);
}
}
impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
fn maybe_codegen_consume_direct(
&mut self,
bx: &mut Bx,
place_ref: mir::PlaceRef<'tcx>,
) -> Option<OperandRef<'tcx, Bx::Value>> {
debug!("maybe_codegen_consume_direct(place_ref={:?})", place_ref);
match self.locals[place_ref.local] {
LocalRef::Operand(mut o) => {
// Moves out of scalar and scalar pair fields are trivial.
for elem in place_ref.projection.iter() {
match elem {
mir::ProjectionElem::Field(ref f, _) => {
assert!(
!o.layout.ty.is_any_ptr(),
"Bad PlaceRef: destructing pointers should use cast/PtrMetadata, \
but tried to access field {f:?} of pointer {o:?}",
);
o = o.extract_field(bx, f.index());
}
mir::ProjectionElem::Index(_)
| mir::ProjectionElem::ConstantIndex { .. } => {
// ZSTs don't require any actual memory access.
// FIXME(eddyb) deduplicate this with the identical
// checks in `codegen_consume` and `extract_field`.
let elem = o.layout.field(bx.cx(), 0);
if elem.is_zst() {
o = OperandRef::zero_sized(elem);
} else {
return None;
}
}
_ => return None,
}
}
Some(o)
}
LocalRef::PendingOperand => {
bug!("use of {:?} before def", place_ref);
}
LocalRef::Place(..) | LocalRef::UnsizedPlace(..) => {
// watch out for locals that do not have an
// alloca; they are handled somewhat differently
None
}
}
}
pub fn codegen_consume(
&mut self,
bx: &mut Bx,
place_ref: mir::PlaceRef<'tcx>,
) -> OperandRef<'tcx, Bx::Value> {
debug!("codegen_consume(place_ref={:?})", place_ref);
let ty = self.monomorphized_place_ty(place_ref);
let layout = bx.cx().layout_of(ty);
// ZSTs don't require any actual memory access.
if layout.is_zst() {
return OperandRef::zero_sized(layout);
}
if let Some(o) = self.maybe_codegen_consume_direct(bx, place_ref) {
return o;
}
// for most places, to consume them we just load them
// out from their home
let place = self.codegen_place(bx, place_ref);
bx.load_operand(place)
}
pub fn codegen_operand(
&mut self,
bx: &mut Bx,
operand: &mir::Operand<'tcx>,
) -> OperandRef<'tcx, Bx::Value> {
debug!("codegen_operand(operand={:?})", operand);
match *operand {
mir::Operand::Copy(ref place) | mir::Operand::Move(ref place) => {
self.codegen_consume(bx, place.as_ref())
}
mir::Operand::Constant(ref constant) => {
let constant_ty = self.monomorphize(constant.ty());
// Most SIMD vector constants should be passed as immediates.
// (In particular, some intrinsics really rely on this.)
if constant_ty.is_simd() {
// However, some SIMD types do not actually use the vector ABI
// (in particular, packed SIMD types do not). Ensure we exclude those.
let layout = bx.layout_of(constant_ty);
if let Abi::Vector { .. } = layout.abi {
let (llval, ty) = self.immediate_const_vector(bx, constant);
return OperandRef {
val: OperandValue::Immediate(llval),
layout: bx.layout_of(ty),
};
}
}
self.eval_mir_constant_to_operand(bx, constant)
}
}
}
}