| use std::fmt; |
| |
| use itertools::Either; |
| use rustc_abi as abi; |
| use rustc_abi::{ |
| Align, BackendRepr, FIRST_VARIANT, FieldIdx, Primitive, Size, TagEncoding, VariantIdx, Variants, |
| }; |
| use rustc_middle::mir::interpret::{Pointer, Scalar, alloc_range}; |
| use rustc_middle::mir::{self, ConstValue}; |
| use rustc_middle::ty::Ty; |
| use rustc_middle::ty::layout::{LayoutOf, TyAndLayout}; |
| use rustc_middle::{bug, span_bug}; |
| use rustc_session::config::OptLevel; |
| use tracing::{debug, instrument}; |
| |
| use super::place::{PlaceRef, PlaceValue}; |
| use super::rvalue::transmute_scalar; |
| use super::{FunctionCx, LocalRef}; |
| use crate::MemFlags; |
| use crate::common::IntPredicate; |
| use crate::traits::*; |
| |
| /// 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 |
| /// [`LayoutTypeCodegenMethods::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 [`LayoutTypeCodegenMethods::backend_type`]. |
| Ref(PlaceValue<V>), |
| /// A single LLVM immediate value. |
| /// |
| /// An `OperandValue` *must* be this variant for any type for which |
| /// [`LayoutTypeCodegenMethods::is_backend_immediate`] returns `true`. |
| /// The backend value in this variant must be the *immediate* backend type, |
| /// as returned by [`LayoutTypeCodegenMethods::immediate_backend_type`]. |
| Immediate(V), |
| /// A pair of immediate LLVM values. Used by wide pointers too. |
| /// |
| /// # Invariants |
| /// - For `Pair(a, b)`, `a` is always at offset 0, but may have `FieldIdx(1..)` |
| /// - `b` is not at offset 0, because `V` is not a 1ZST type. |
| /// - `a` and `b` will have a different FieldIdx, but otherwise `b`'s may be lower |
| /// or they may not be adjacent, due to arbitrary numbers of 1ZST fields that |
| /// will not affect the shape of the data which determines if `Pair` will be used. |
| /// - An `OperandValue` *must* be this variant for any type for which |
| /// [`LayoutTypeCodegenMethods::is_backend_scalar_pair`] returns `true`. |
| /// - The backend values in this variant must be the *immediate* backend types, |
| /// as returned by [`LayoutTypeCodegenMethods::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 [`ConstCodegenMethods::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> { |
| /// 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(crate) 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(crate) 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: LayoutTypeCodegenMethods<'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(crate) fn from_const<Bx: BuilderMethods<'a, 'tcx, Value = V>>( |
| bx: &mut Bx, |
| val: mir::ConstValue, |
| ty: Ty<'tcx>, |
| ) -> Self { |
| let layout = bx.layout_of(ty); |
| |
| let val = match val { |
| ConstValue::Scalar(x) => { |
| let BackendRepr::Scalar(scalar) = layout.backend_repr 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 { alloc_id, meta } => { |
| let BackendRepr::ScalarPair(a_scalar, _) = layout.backend_repr else { |
| bug!("from_const: invalid ScalarPair layout: {:#?}", layout); |
| }; |
| let a = Scalar::from_pointer(Pointer::new(alloc_id.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, "{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::Primitive::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.backend_repr { |
| BackendRepr::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 } |
| } |
| BackendRepr::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: CodegenMethods<'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 BackendRepr::ScalarPair(..) = layout.backend_repr { |
| 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(crate) fn extract_field<Bx: BuilderMethods<'a, 'tcx, Value = V>>( |
| &self, |
| fx: &mut FunctionCx<'a, 'tcx, Bx>, |
| bx: &mut Bx, |
| i: usize, |
| ) -> Self { |
| let field = self.layout.field(bx.cx(), i); |
| let offset = self.layout.fields.offset(i); |
| |
| if !bx.is_backend_ref(self.layout) && bx.is_backend_ref(field) { |
| // Part of https://github.com/rust-lang/compiler-team/issues/838 |
| span_bug!( |
| fx.mir.span, |
| "Non-ref type {self:?} cannot project to ref field type {field:?}", |
| ); |
| } |
| |
| let val = if field.is_zst() { |
| OperandValue::ZeroSized |
| } else if field.size == self.layout.size { |
| assert_eq!(offset.bytes(), 0); |
| fx.codegen_transmute_operand(bx, *self, field) |
| } else { |
| let (in_scalar, imm) = match (self.val, self.layout.backend_repr) { |
| // Extract a scalar component from a pair. |
| (OperandValue::Pair(a_llval, b_llval), BackendRepr::ScalarPair(a, b)) => { |
| if offset.bytes() == 0 { |
| assert_eq!(field.size, a.size(bx.cx())); |
| (Some(a), 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())); |
| (Some(b), b_llval) |
| } |
| } |
| |
| _ => { |
| span_bug!(fx.mir.span, "OperandRef::extract_field({:?}): not applicable", self) |
| } |
| }; |
| OperandValue::Immediate(match field.backend_repr { |
| BackendRepr::SimdVector { .. } => imm, |
| BackendRepr::Scalar(out_scalar) => { |
| let Some(in_scalar) = in_scalar else { |
| span_bug!( |
| fx.mir.span, |
| "OperandRef::extract_field({:?}): missing input scalar for output scalar", |
| self |
| ) |
| }; |
| if in_scalar != out_scalar { |
| // If the backend and backend_immediate types might differ, |
| // flip back to the backend type then to the new immediate. |
| // This avoids nop truncations, but still handles things like |
| // Bools in union fields needs to be truncated. |
| let backend = bx.from_immediate(imm); |
| bx.to_immediate_scalar(backend, out_scalar) |
| } else { |
| imm |
| } |
| } |
| BackendRepr::ScalarPair(_, _) | BackendRepr::Memory { .. } => bug!(), |
| }) |
| }; |
| |
| OperandRef { val, layout: field } |
| } |
| |
| /// Obtain the actual discriminant of a value. |
| #[instrument(level = "trace", skip(fx, bx))] |
| pub fn codegen_get_discr<Bx: BuilderMethods<'a, 'tcx, Value = V>>( |
| self, |
| fx: &mut FunctionCx<'a, 'tcx, Bx>, |
| bx: &mut Bx, |
| cast_to: Ty<'tcx>, |
| ) -> V { |
| let dl = &bx.tcx().data_layout; |
| let cast_to_layout = bx.cx().layout_of(cast_to); |
| let cast_to = bx.cx().immediate_backend_type(cast_to_layout); |
| |
| // We check uninhabitedness separately because a type like |
| // `enum Foo { Bar(i32, !) }` is still reported as `Variants::Single`, |
| // *not* as `Variants::Empty`. |
| if self.layout.is_uninhabited() { |
| return bx.cx().const_poison(cast_to); |
| } |
| |
| let (tag_scalar, tag_encoding, tag_field) = match self.layout.variants { |
| Variants::Empty => unreachable!("we already handled uninhabited types"), |
| Variants::Single { index } => { |
| let discr_val = |
| if let Some(discr) = self.layout.ty.discriminant_for_variant(bx.tcx(), index) { |
| discr.val |
| } else { |
| // This arm is for types which are neither enums nor coroutines, |
| // and thus for which the only possible "variant" should be the first one. |
| assert_eq!(index, FIRST_VARIANT); |
| // There's thus no actual discriminant to return, so we return |
| // what it would have been if this was a single-variant enum. |
| 0 |
| }; |
| return bx.cx().const_uint_big(cast_to, discr_val); |
| } |
| Variants::Multiple { tag, ref tag_encoding, tag_field, .. } => { |
| (tag, tag_encoding, tag_field) |
| } |
| }; |
| |
| // Read the tag/niche-encoded discriminant from memory. |
| let tag_op = match self.val { |
| OperandValue::ZeroSized => bug!(), |
| OperandValue::Immediate(_) | OperandValue::Pair(_, _) => { |
| self.extract_field(fx, bx, tag_field.as_usize()) |
| } |
| OperandValue::Ref(place) => { |
| let tag = place.with_type(self.layout).project_field(bx, tag_field.as_usize()); |
| bx.load_operand(tag) |
| } |
| }; |
| let tag_imm = tag_op.immediate(); |
| |
| // Decode the discriminant (specifically if it's niche-encoded). |
| match *tag_encoding { |
| TagEncoding::Direct => { |
| let signed = match tag_scalar.primitive() { |
| // We use `i1` for bytes that are always `0` or `1`, |
| // e.g., `#[repr(i8)] enum E { A, B }`, but we can't |
| // let LLVM interpret the `i1` as signed, because |
| // then `i1 1` (i.e., `E::B`) is effectively `i8 -1`. |
| Primitive::Int(_, signed) => !tag_scalar.is_bool() && signed, |
| _ => false, |
| }; |
| bx.intcast(tag_imm, cast_to, signed) |
| } |
| TagEncoding::Niche { untagged_variant, ref niche_variants, niche_start } => { |
| // Cast to an integer so we don't have to treat a pointer as a |
| // special case. |
| let (tag, tag_llty) = match tag_scalar.primitive() { |
| // FIXME(erikdesjardins): handle non-default addrspace ptr sizes |
| Primitive::Pointer(_) => { |
| let t = bx.type_from_integer(dl.ptr_sized_integer()); |
| let tag = bx.ptrtoint(tag_imm, t); |
| (tag, t) |
| } |
| _ => (tag_imm, bx.cx().immediate_backend_type(tag_op.layout)), |
| }; |
| |
| // `layout_sanity_check` ensures that we only get here for cases where the discriminant |
| // value and the variant index match, since that's all `Niche` can encode. |
| |
| let relative_max = niche_variants.end().as_u32() - niche_variants.start().as_u32(); |
| let niche_start_const = bx.cx().const_uint_big(tag_llty, niche_start); |
| |
| // We have a subrange `niche_start..=niche_end` inside `range`. |
| // If the value of the tag is inside this subrange, it's a |
| // "niche value", an increment of the discriminant. Otherwise it |
| // indicates the untagged variant. |
| // A general algorithm to extract the discriminant from the tag |
| // is: |
| // relative_tag = tag - niche_start |
| // is_niche = relative_tag <= (ule) relative_max |
| // discr = if is_niche { |
| // cast(relative_tag) + niche_variants.start() |
| // } else { |
| // untagged_variant |
| // } |
| // However, we will likely be able to emit simpler code. |
| let (is_niche, tagged_discr, delta) = if relative_max == 0 { |
| // Best case scenario: only one tagged variant. This will |
| // likely become just a comparison and a jump. |
| // The algorithm is: |
| // is_niche = tag == niche_start |
| // discr = if is_niche { |
| // niche_start |
| // } else { |
| // untagged_variant |
| // } |
| let is_niche = bx.icmp(IntPredicate::IntEQ, tag, niche_start_const); |
| let tagged_discr = |
| bx.cx().const_uint(cast_to, niche_variants.start().as_u32() as u64); |
| (is_niche, tagged_discr, 0) |
| } else { |
| // Thanks to parameter attributes and load metadata, LLVM already knows |
| // the general valid range of the tag. It's possible, though, for there |
| // to be an impossible value *in the middle*, which those ranges don't |
| // communicate, so it's worth an `assume` to let the optimizer know. |
| // Most importantly, this means when optimizing a variant test like |
| // `SELECT(is_niche, complex, CONST) == CONST` it's ok to simplify that |
| // to `!is_niche` because the `complex` part can't possibly match. |
| // |
| // This was previously asserted on `tagged_discr` below, where the |
| // impossible value is more obvious, but that caused an intermediate |
| // value to become multi-use and thus not optimize, so instead this |
| // assumes on the original input which is always multi-use. See |
| // <https://github.com/llvm/llvm-project/issues/134024#issuecomment-3131782555> |
| // |
| // FIXME: If we ever get range assume operand bundles in LLVM (so we |
| // don't need the `icmp`s in the instruction stream any more), it |
| // might be worth moving this back to being on the switch argument |
| // where it's more obviously applicable. |
| if niche_variants.contains(&untagged_variant) |
| && bx.cx().sess().opts.optimize != OptLevel::No |
| { |
| let impossible = niche_start |
| .wrapping_add(u128::from(untagged_variant.as_u32())) |
| .wrapping_sub(u128::from(niche_variants.start().as_u32())); |
| let impossible = bx.cx().const_uint_big(tag_llty, impossible); |
| let ne = bx.icmp(IntPredicate::IntNE, tag, impossible); |
| bx.assume(ne); |
| } |
| |
| // With multiple niched variants we'll have to actually compute |
| // the variant index from the stored tag. |
| // |
| // However, there's still one small optimization we can often do for |
| // determining *whether* a tag value is a natural value or a niched |
| // variant. The general algorithm involves a subtraction that often |
| // wraps in practice, making it tricky to analyse. However, in cases |
| // where there are few enough possible values of the tag that it doesn't |
| // need to wrap around, we can instead just look for the contiguous |
| // tag values on the end of the range with a single comparison. |
| // |
| // For example, take the type `enum Demo { A, B, Untagged(bool) }`. |
| // The `bool` is {0, 1}, and the two other variants are given the |
| // tags {2, 3} respectively. That means the `tag_range` is |
| // `[0, 3]`, which doesn't wrap as unsigned (nor as signed), so |
| // we can test for the niched variants with just `>= 2`. |
| // |
| // That means we're looking either for the niche values *above* |
| // the natural values of the untagged variant: |
| // |
| // niche_start niche_end |
| // | | |
| // v v |
| // MIN -------------+---------------------------+---------- MAX |
| // ^ | is niche | |
| // | +---------------------------+ |
| // | | |
| // tag_range.start tag_range.end |
| // |
| // Or *below* the natural values: |
| // |
| // niche_start niche_end |
| // | | |
| // v v |
| // MIN ----+-----------------------+---------------------- MAX |
| // | is niche | ^ |
| // +-----------------------+ | |
| // | | |
| // tag_range.start tag_range.end |
| // |
| // With those two options and having the flexibility to choose |
| // between a signed or unsigned comparison on the tag, that |
| // covers most realistic scenarios. The tests have a (contrived) |
| // example of a 1-byte enum with over 128 niched variants which |
| // wraps both as signed as unsigned, though, and for something |
| // like that we're stuck with the general algorithm. |
| |
| let tag_range = tag_scalar.valid_range(&dl); |
| let tag_size = tag_scalar.size(&dl); |
| let niche_end = u128::from(relative_max).wrapping_add(niche_start); |
| let niche_end = tag_size.truncate(niche_end); |
| |
| let relative_discr = bx.sub(tag, niche_start_const); |
| let cast_tag = bx.intcast(relative_discr, cast_to, false); |
| let is_niche = if tag_range.no_unsigned_wraparound(tag_size) == Ok(true) { |
| if niche_start == tag_range.start { |
| let niche_end_const = bx.cx().const_uint_big(tag_llty, niche_end); |
| bx.icmp(IntPredicate::IntULE, tag, niche_end_const) |
| } else { |
| assert_eq!(niche_end, tag_range.end); |
| bx.icmp(IntPredicate::IntUGE, tag, niche_start_const) |
| } |
| } else if tag_range.no_signed_wraparound(tag_size) == Ok(true) { |
| if niche_start == tag_range.start { |
| let niche_end_const = bx.cx().const_uint_big(tag_llty, niche_end); |
| bx.icmp(IntPredicate::IntSLE, tag, niche_end_const) |
| } else { |
| assert_eq!(niche_end, tag_range.end); |
| bx.icmp(IntPredicate::IntSGE, tag, niche_start_const) |
| } |
| } else { |
| bx.icmp( |
| IntPredicate::IntULE, |
| relative_discr, |
| bx.cx().const_uint(tag_llty, relative_max as u64), |
| ) |
| }; |
| |
| (is_niche, cast_tag, niche_variants.start().as_u32() as u128) |
| }; |
| |
| let tagged_discr = if delta == 0 { |
| tagged_discr |
| } else { |
| bx.add(tagged_discr, bx.cx().const_uint_big(cast_to, delta)) |
| }; |
| |
| let untagged_variant_const = |
| bx.cx().const_uint(cast_to, u64::from(untagged_variant.as_u32())); |
| |
| let discr = bx.select(is_niche, tagged_discr, untagged_variant_const); |
| |
| // In principle we could insert assumes on the possible range of `discr`, but |
| // currently in LLVM this isn't worth it because the original `tag` will |
| // have either a `range` parameter attribute or `!range` metadata, |
| // or come from a `transmute` that already `assume`d it. |
| |
| discr |
| } |
| } |
| } |
| } |
| |
| /// Each of these variants starts out as `Either::Right` when it's uninitialized, |
| /// then setting the field changes that to `Either::Left` with the backend value. |
| #[derive(Debug, Copy, Clone)] |
| enum OperandValueBuilder<V> { |
| ZeroSized, |
| Immediate(Either<V, abi::Scalar>), |
| Pair(Either<V, abi::Scalar>, Either<V, abi::Scalar>), |
| /// `repr(simd)` types need special handling because they each have a non-empty |
| /// array field (which uses [`OperandValue::Ref`]) despite the SIMD type itself |
| /// using [`OperandValue::Immediate`] which for any other kind of type would |
| /// mean that its one non-ZST field would also be [`OperandValue::Immediate`]. |
| Vector(Either<V, ()>), |
| } |
| |
| /// Allows building up an `OperandRef` by setting fields one at a time. |
| #[derive(Debug, Copy, Clone)] |
| pub(super) struct OperandRefBuilder<'tcx, V> { |
| val: OperandValueBuilder<V>, |
| layout: TyAndLayout<'tcx>, |
| } |
| |
| impl<'a, 'tcx, V: CodegenObject> OperandRefBuilder<'tcx, V> { |
| /// Creates an uninitialized builder for an instance of the `layout`. |
| /// |
| /// ICEs for [`BackendRepr::Memory`] types (other than ZSTs), which should |
| /// be built up inside a [`PlaceRef`] instead as they need an allocated place |
| /// into which to write the values of the fields. |
| pub(super) fn new(layout: TyAndLayout<'tcx>) -> Self { |
| let val = match layout.backend_repr { |
| BackendRepr::Memory { .. } if layout.is_zst() => OperandValueBuilder::ZeroSized, |
| BackendRepr::Scalar(s) => OperandValueBuilder::Immediate(Either::Right(s)), |
| BackendRepr::ScalarPair(a, b) => { |
| OperandValueBuilder::Pair(Either::Right(a), Either::Right(b)) |
| } |
| BackendRepr::SimdVector { .. } => OperandValueBuilder::Vector(Either::Right(())), |
| BackendRepr::Memory { .. } => { |
| bug!("Cannot use non-ZST Memory-ABI type in operand builder: {layout:?}"); |
| } |
| }; |
| OperandRefBuilder { val, layout } |
| } |
| |
| pub(super) fn insert_field<Bx: BuilderMethods<'a, 'tcx, Value = V>>( |
| &mut self, |
| bx: &mut Bx, |
| variant: VariantIdx, |
| field: FieldIdx, |
| field_operand: OperandRef<'tcx, V>, |
| ) { |
| if let OperandValue::ZeroSized = field_operand.val { |
| // A ZST never adds any state, so just ignore it. |
| // This special-casing is worth it because of things like |
| // `Result<!, !>` where `Ok(never)` is legal to write, |
| // but the type shows as FieldShape::Primitive so we can't |
| // actually look at the layout for the field being set. |
| return; |
| } |
| |
| let is_zero_offset = if let abi::FieldsShape::Primitive = self.layout.fields { |
| // The other branch looking at field layouts ICEs for primitives, |
| // so we need to handle them separately. |
| // Because we handled ZSTs above (like the metadata in a thin pointer), |
| // the only possibility is that we're setting the one-and-only field. |
| assert!(!self.layout.is_zst()); |
| assert_eq!(variant, FIRST_VARIANT); |
| assert_eq!(field, FieldIdx::ZERO); |
| true |
| } else { |
| let variant_layout = self.layout.for_variant(bx.cx(), variant); |
| let field_offset = variant_layout.fields.offset(field.as_usize()); |
| field_offset == Size::ZERO |
| }; |
| |
| let mut update = |tgt: &mut Either<V, abi::Scalar>, src, from_scalar| { |
| let to_scalar = tgt.unwrap_right(); |
| // We transmute here (rather than just `from_immediate`) because in |
| // `Result<usize, *const ()>` the field of the `Ok` is an integer, |
| // but the corresponding scalar in the enum is a pointer. |
| let imm = transmute_scalar(bx, src, from_scalar, to_scalar); |
| *tgt = Either::Left(imm); |
| }; |
| |
| match (field_operand.val, field_operand.layout.backend_repr) { |
| (OperandValue::ZeroSized, _) => unreachable!("Handled above"), |
| (OperandValue::Immediate(v), BackendRepr::Scalar(from_scalar)) => match &mut self.val { |
| OperandValueBuilder::Immediate(val @ Either::Right(_)) if is_zero_offset => { |
| update(val, v, from_scalar); |
| } |
| OperandValueBuilder::Pair(fst @ Either::Right(_), _) if is_zero_offset => { |
| update(fst, v, from_scalar); |
| } |
| OperandValueBuilder::Pair(_, snd @ Either::Right(_)) if !is_zero_offset => { |
| update(snd, v, from_scalar); |
| } |
| _ => { |
| bug!("Tried to insert {field_operand:?} into {variant:?}.{field:?} of {self:?}") |
| } |
| }, |
| (OperandValue::Immediate(v), BackendRepr::SimdVector { .. }) => match &mut self.val { |
| OperandValueBuilder::Vector(val @ Either::Right(())) if is_zero_offset => { |
| *val = Either::Left(v); |
| } |
| _ => { |
| bug!("Tried to insert {field_operand:?} into {variant:?}.{field:?} of {self:?}") |
| } |
| }, |
| (OperandValue::Pair(a, b), BackendRepr::ScalarPair(from_sa, from_sb)) => { |
| match &mut self.val { |
| OperandValueBuilder::Pair(fst @ Either::Right(_), snd @ Either::Right(_)) => { |
| update(fst, a, from_sa); |
| update(snd, b, from_sb); |
| } |
| _ => bug!( |
| "Tried to insert {field_operand:?} into {variant:?}.{field:?} of {self:?}" |
| ), |
| } |
| } |
| (OperandValue::Ref(place), BackendRepr::Memory { .. }) => match &mut self.val { |
| OperandValueBuilder::Vector(val @ Either::Right(())) => { |
| let ibty = bx.cx().immediate_backend_type(self.layout); |
| let simd = bx.load_from_place(ibty, place); |
| *val = Either::Left(simd); |
| } |
| _ => { |
| bug!("Tried to insert {field_operand:?} into {variant:?}.{field:?} of {self:?}") |
| } |
| }, |
| _ => bug!("Operand cannot be used with `insert_field`: {field_operand:?}"), |
| } |
| } |
| |
| /// Insert the immediate value `imm` for field `f` in the *type itself*, |
| /// rather than into one of the variants. |
| /// |
| /// Most things want [`Self::insert_field`] instead, but this one is |
| /// necessary for writing things like enum tags that aren't in any variant. |
| pub(super) fn insert_imm(&mut self, f: FieldIdx, imm: V) { |
| let field_offset = self.layout.fields.offset(f.as_usize()); |
| let is_zero_offset = field_offset == Size::ZERO; |
| match &mut self.val { |
| OperandValueBuilder::Immediate(val @ Either::Right(_)) if is_zero_offset => { |
| *val = Either::Left(imm); |
| } |
| OperandValueBuilder::Pair(fst @ Either::Right(_), _) if is_zero_offset => { |
| *fst = Either::Left(imm); |
| } |
| OperandValueBuilder::Pair(_, snd @ Either::Right(_)) if !is_zero_offset => { |
| *snd = Either::Left(imm); |
| } |
| _ => bug!("Tried to insert {imm:?} into field {f:?} of {self:?}"), |
| } |
| } |
| |
| /// After having set all necessary fields, this converts the builder back |
| /// to the normal `OperandRef`. |
| /// |
| /// ICEs if any required fields were not set. |
| pub(super) fn build(&self, cx: &impl CodegenMethods<'tcx, Value = V>) -> OperandRef<'tcx, V> { |
| let OperandRefBuilder { val, layout } = *self; |
| |
| // For something like `Option::<u32>::None`, it's expected that the |
| // payload scalar will not actually have been set, so this converts |
| // unset scalars to corresponding `undef` values so long as the scalar |
| // from the layout allows uninit. |
| let unwrap = |r: Either<V, abi::Scalar>| match r { |
| Either::Left(v) => v, |
| Either::Right(s) if s.is_uninit_valid() => { |
| let bty = cx.type_from_scalar(s); |
| cx.const_undef(bty) |
| } |
| Either::Right(_) => bug!("OperandRef::build called while fields are missing {self:?}"), |
| }; |
| |
| let val = match val { |
| OperandValueBuilder::ZeroSized => OperandValue::ZeroSized, |
| OperandValueBuilder::Immediate(v) => OperandValue::Immediate(unwrap(v)), |
| OperandValueBuilder::Pair(a, b) => OperandValue::Pair(unwrap(a), unwrap(b)), |
| OperandValueBuilder::Vector(v) => match v { |
| Either::Left(v) => OperandValue::Immediate(v), |
| Either::Right(()) |
| if let BackendRepr::SimdVector { element, .. } = layout.backend_repr |
| && element.is_uninit_valid() => |
| { |
| let bty = cx.immediate_backend_type(layout); |
| OperandValue::Immediate(cx.const_undef(bty)) |
| } |
| Either::Right(()) => { |
| bug!("OperandRef::build called while fields are missing {self:?}") |
| } |
| }, |
| }; |
| OperandRef { val, layout } |
| } |
| } |
| |
| 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 BackendRepr::ScalarPair(a_scalar, b_scalar) = dest.layout.backend_repr 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); |
| } |
| } |
| } |
| } |
| |
| 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) => { |
| // We only need to handle the projections that |
| // `LocalAnalyzer::process_place` let make it here. |
| for elem in place_ref.projection { |
| match *elem { |
| mir::ProjectionElem::Field(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(self, bx, f.index()); |
| } |
| mir::PlaceElem::Downcast(_, vidx) => { |
| debug_assert_eq!( |
| o.layout.variants, |
| abi::Variants::Single { index: vidx }, |
| ); |
| let layout = o.layout.for_variant(bx.cx(), vidx); |
| o = OperandRef { val: o.val, layout } |
| } |
| mir::PlaceElem::Subtype(subtype_ty) => { |
| let subtype_ty = self.monomorphize(subtype_ty); |
| let layout = self.cx.layout_of(subtype_ty); |
| o = OperandRef { val: o.val, layout } |
| } |
| _ => 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 BackendRepr::SimdVector { .. } = layout.backend_repr { |
| 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) |
| } |
| } |
| } |
| } |
