diff options
Diffstat (limited to '')
| -rw-r--r-- | compiler/rustc_middle/src/ty/consts.rs | 326 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/consts/int.rs | 483 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/consts/kind.rs | 239 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/consts/valtree.rs | 104 |
4 files changed, 1152 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs new file mode 100644 index 000000000..f8792edc0 --- /dev/null +++ b/compiler/rustc_middle/src/ty/consts.rs @@ -0,0 +1,326 @@ +use crate::mir::interpret::LitToConstInput; +use crate::mir::ConstantKind; +use crate::ty::{ + self, InlineConstSubsts, InlineConstSubstsParts, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, + TyCtxt, TypeVisitable, +}; +use rustc_data_structures::intern::Interned; +use rustc_errors::ErrorGuaranteed; +use rustc_hir as hir; +use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_macros::HashStable; +use std::fmt; + +mod int; +mod kind; +mod valtree; + +pub use int::*; +pub use kind::*; +pub use valtree::*; + +/// Use this rather than `ConstS`, whenever possible. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)] +#[rustc_pass_by_value] +pub struct Const<'tcx>(pub Interned<'tcx, ConstS<'tcx>>); + +impl<'tcx> fmt::Debug for Const<'tcx> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + // This reflects what `Const` looked liked before `Interned` was + // introduced. We print it like this to avoid having to update expected + // output in a lot of tests. + write!(f, "Const {{ ty: {:?}, kind: {:?} }}", self.ty(), self.kind()) + } +} + +/// Typed constant value. +#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, HashStable, TyEncodable, TyDecodable)] +pub struct ConstS<'tcx> { + pub ty: Ty<'tcx>, + pub kind: ConstKind<'tcx>, +} + +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +static_assert_size!(ConstS<'_>, 48); + +impl<'tcx> Const<'tcx> { + #[inline] + pub fn ty(self) -> Ty<'tcx> { + self.0.ty + } + + #[inline] + pub fn kind(self) -> ConstKind<'tcx> { + self.0.kind + } + + /// Literals and const generic parameters are eagerly converted to a constant, everything else + /// becomes `Unevaluated`. + pub fn from_anon_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self { + Self::from_opt_const_arg_anon_const(tcx, ty::WithOptConstParam::unknown(def_id)) + } + + #[instrument(skip(tcx), level = "debug")] + pub fn from_opt_const_arg_anon_const( + tcx: TyCtxt<'tcx>, + def: ty::WithOptConstParam<LocalDefId>, + ) -> Self { + debug!("Const::from_anon_const(def={:?})", def); + + let body_id = match tcx.hir().get_by_def_id(def.did) { + hir::Node::AnonConst(ac) => ac.body, + _ => span_bug!( + tcx.def_span(def.did.to_def_id()), + "from_anon_const can only process anonymous constants" + ), + }; + + let expr = &tcx.hir().body(body_id).value; + debug!(?expr); + + let ty = tcx.type_of(def.def_id_for_type_of()); + + match Self::try_eval_lit_or_param(tcx, ty, expr) { + Some(v) => v, + None => tcx.mk_const(ty::ConstS { + kind: ty::ConstKind::Unevaluated(ty::Unevaluated { + def: def.to_global(), + substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()), + promoted: None, + }), + ty, + }), + } + } + + #[instrument(skip(tcx), level = "debug")] + fn try_eval_lit_or_param( + tcx: TyCtxt<'tcx>, + ty: Ty<'tcx>, + expr: &'tcx hir::Expr<'tcx>, + ) -> Option<Self> { + // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments + // currently have to be wrapped in curly brackets, so it's necessary to special-case. + let expr = match &expr.kind { + hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => { + block.expr.as_ref().unwrap() + } + _ => expr, + }; + + let lit_input = match expr.kind { + hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }), + hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => match expr.kind { + hir::ExprKind::Lit(ref lit) => { + Some(LitToConstInput { lit: &lit.node, ty, neg: true }) + } + _ => None, + }, + _ => None, + }; + + if let Some(lit_input) = lit_input { + // If an error occurred, ignore that it's a literal and leave reporting the error up to + // mir. + match tcx.at(expr.span).lit_to_const(lit_input) { + Ok(c) => return Some(c), + Err(e) => { + tcx.sess.delay_span_bug( + expr.span, + &format!("Const::from_anon_const: couldn't lit_to_const {:?}", e), + ); + } + } + } + + use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath}; + match expr.kind { + ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => { + // Find the name and index of the const parameter by indexing the generics of + // the parent item and construct a `ParamConst`. + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); + let item_id = tcx.hir().get_parent_node(hir_id); + let item_def_id = tcx.hir().local_def_id(item_id); + let generics = tcx.generics_of(item_def_id.to_def_id()); + let index = generics.param_def_id_to_index[&def_id]; + let name = tcx.hir().name(hir_id); + Some(tcx.mk_const(ty::ConstS { + kind: ty::ConstKind::Param(ty::ParamConst::new(index, name)), + ty, + })) + } + _ => None, + } + } + + pub fn from_inline_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self { + debug!("Const::from_inline_const(def_id={:?})", def_id); + + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); + + let body_id = match tcx.hir().get(hir_id) { + hir::Node::AnonConst(ac) => ac.body, + _ => span_bug!( + tcx.def_span(def_id.to_def_id()), + "from_inline_const can only process anonymous constants" + ), + }; + + let expr = &tcx.hir().body(body_id).value; + + let ty = tcx.typeck(def_id).node_type(hir_id); + + let ret = match Self::try_eval_lit_or_param(tcx, ty, expr) { + Some(v) => v, + None => { + let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()); + let parent_substs = + tcx.erase_regions(InternalSubsts::identity_for_item(tcx, typeck_root_def_id)); + let substs = + InlineConstSubsts::new(tcx, InlineConstSubstsParts { parent_substs, ty }) + .substs; + tcx.mk_const(ty::ConstS { + kind: ty::ConstKind::Unevaluated(ty::Unevaluated { + def: ty::WithOptConstParam::unknown(def_id).to_global(), + substs, + promoted: None, + }), + ty, + }) + } + }; + debug_assert!(!ret.has_free_regions()); + ret + } + + /// Interns the given value as a constant. + #[inline] + pub fn from_value(tcx: TyCtxt<'tcx>, val: ty::ValTree<'tcx>, ty: Ty<'tcx>) -> Self { + tcx.mk_const(ConstS { kind: ConstKind::Value(val), ty }) + } + + /// Panics if self.kind != ty::ConstKind::Value + pub fn to_valtree(self) -> ty::ValTree<'tcx> { + match self.kind() { + ty::ConstKind::Value(valtree) => valtree, + _ => bug!("expected ConstKind::Value, got {:?}", self.kind()), + } + } + + pub fn from_scalar_int(tcx: TyCtxt<'tcx>, i: ScalarInt, ty: Ty<'tcx>) -> Self { + let valtree = ty::ValTree::from_scalar_int(i); + Self::from_value(tcx, valtree, ty) + } + + #[inline] + /// Creates a constant with the given integer value and interns it. + pub fn from_bits(tcx: TyCtxt<'tcx>, bits: u128, ty: ParamEnvAnd<'tcx, Ty<'tcx>>) -> Self { + let size = tcx + .layout_of(ty) + .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e)) + .size; + Self::from_scalar_int(tcx, ScalarInt::try_from_uint(bits, size).unwrap(), ty.value) + } + + #[inline] + /// Creates an interned zst constant. + pub fn zero_sized(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self { + let valtree = ty::ValTree::zst(); + Self::from_value(tcx, valtree, ty) + } + + #[inline] + /// Creates an interned bool constant. + pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> Self { + Self::from_bits(tcx, v as u128, ParamEnv::empty().and(tcx.types.bool)) + } + + #[inline] + /// Creates an interned usize constant. + pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self { + Self::from_bits(tcx, n as u128, ParamEnv::empty().and(tcx.types.usize)) + } + + #[inline] + /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of + /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it + /// contains const generic parameters or pointers). + pub fn try_eval_bits( + self, + tcx: TyCtxt<'tcx>, + param_env: ParamEnv<'tcx>, + ty: Ty<'tcx>, + ) -> Option<u128> { + assert_eq!(self.ty(), ty); + let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size; + // if `ty` does not depend on generic parameters, use an empty param_env + self.kind().eval(tcx, param_env).try_to_bits(size) + } + + #[inline] + pub fn try_eval_bool(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> { + self.kind().eval(tcx, param_env).try_to_bool() + } + + #[inline] + pub fn try_eval_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u64> { + self.kind().eval(tcx, param_env).try_to_machine_usize(tcx) + } + + #[inline] + /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the + /// unevaluated constant. + pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Const<'tcx> { + if let Some(val) = self.kind().try_eval_for_typeck(tcx, param_env) { + match val { + Ok(val) => Const::from_value(tcx, val, self.ty()), + Err(ErrorGuaranteed { .. }) => tcx.const_error(self.ty()), + } + } else { + // Either the constant isn't evaluatable or ValTree creation failed. + self + } + } + + #[inline] + /// Tries to evaluate the constant if it is `Unevaluated` and creates a ConstValue if the + /// evaluation succeeds. If it doesn't succeed, returns the unevaluated constant. + pub fn eval_for_mir(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> ConstantKind<'tcx> { + if let Some(val) = self.kind().try_eval_for_mir(tcx, param_env) { + match val { + Ok(const_val) => ConstantKind::from_value(const_val, self.ty()), + Err(ErrorGuaranteed { .. }) => ConstantKind::Ty(tcx.const_error(self.ty())), + } + } else { + ConstantKind::Ty(self) + } + } + + #[inline] + /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type. + pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 { + self.try_eval_bits(tcx, param_env, ty) + .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self)) + } + + #[inline] + /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`. + pub fn eval_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 { + self.try_eval_usize(tcx, param_env) + .unwrap_or_else(|| bug!("expected usize, got {:#?}", self)) + } +} + +pub fn const_param_default<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Const<'tcx> { + let default_def_id = match tcx.hir().get_by_def_id(def_id.expect_local()) { + hir::Node::GenericParam(hir::GenericParam { + kind: hir::GenericParamKind::Const { ty: _, default: Some(ac) }, + .. + }) => tcx.hir().local_def_id(ac.hir_id), + _ => span_bug!( + tcx.def_span(def_id), + "`const_param_default` expected a generic parameter with a constant" + ), + }; + Const::from_anon_const(tcx, default_def_id) +} diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs new file mode 100644 index 000000000..7436f0f6f --- /dev/null +++ b/compiler/rustc_middle/src/ty/consts/int.rs @@ -0,0 +1,483 @@ +use rustc_apfloat::ieee::{Double, Single}; +use rustc_apfloat::Float; +use rustc_serialize::{Decodable, Decoder, Encodable, Encoder}; +use rustc_target::abi::Size; +use std::convert::{TryFrom, TryInto}; +use std::fmt; +use std::num::NonZeroU8; + +use crate::ty::TyCtxt; + +#[derive(Copy, Clone)] +/// A type for representing any integer. Only used for printing. +pub struct ConstInt { + /// The "untyped" variant of `ConstInt`. + int: ScalarInt, + /// Whether the value is of a signed integer type. + signed: bool, + /// Whether the value is a `usize` or `isize` type. + is_ptr_sized_integral: bool, +} + +impl ConstInt { + pub fn new(int: ScalarInt, signed: bool, is_ptr_sized_integral: bool) -> Self { + Self { int, signed, is_ptr_sized_integral } + } +} + +impl std::fmt::Debug for ConstInt { + fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + let Self { int, signed, is_ptr_sized_integral } = *self; + let size = int.size().bytes(); + let raw = int.data; + if signed { + let bit_size = size * 8; + let min = 1u128 << (bit_size - 1); + let max = min - 1; + if raw == min { + match (size, is_ptr_sized_integral) { + (_, true) => write!(fmt, "isize::MIN"), + (1, _) => write!(fmt, "i8::MIN"), + (2, _) => write!(fmt, "i16::MIN"), + (4, _) => write!(fmt, "i32::MIN"), + (8, _) => write!(fmt, "i64::MIN"), + (16, _) => write!(fmt, "i128::MIN"), + _ => bug!("ConstInt 0x{:x} with size = {} and signed = {}", raw, size, signed), + } + } else if raw == max { + match (size, is_ptr_sized_integral) { + (_, true) => write!(fmt, "isize::MAX"), + (1, _) => write!(fmt, "i8::MAX"), + (2, _) => write!(fmt, "i16::MAX"), + (4, _) => write!(fmt, "i32::MAX"), + (8, _) => write!(fmt, "i64::MAX"), + (16, _) => write!(fmt, "i128::MAX"), + _ => bug!("ConstInt 0x{:x} with size = {} and signed = {}", raw, size, signed), + } + } else { + match size { + 1 => write!(fmt, "{}", raw as i8)?, + 2 => write!(fmt, "{}", raw as i16)?, + 4 => write!(fmt, "{}", raw as i32)?, + 8 => write!(fmt, "{}", raw as i64)?, + 16 => write!(fmt, "{}", raw as i128)?, + _ => bug!("ConstInt 0x{:x} with size = {} and signed = {}", raw, size, signed), + } + if fmt.alternate() { + match (size, is_ptr_sized_integral) { + (_, true) => write!(fmt, "_isize")?, + (1, _) => write!(fmt, "_i8")?, + (2, _) => write!(fmt, "_i16")?, + (4, _) => write!(fmt, "_i32")?, + (8, _) => write!(fmt, "_i64")?, + (16, _) => write!(fmt, "_i128")?, + _ => bug!(), + } + } + Ok(()) + } + } else { + let max = Size::from_bytes(size).truncate(u128::MAX); + if raw == max { + match (size, is_ptr_sized_integral) { + (_, true) => write!(fmt, "usize::MAX"), + (1, _) => write!(fmt, "u8::MAX"), + (2, _) => write!(fmt, "u16::MAX"), + (4, _) => write!(fmt, "u32::MAX"), + (8, _) => write!(fmt, "u64::MAX"), + (16, _) => write!(fmt, "u128::MAX"), + _ => bug!("ConstInt 0x{:x} with size = {} and signed = {}", raw, size, signed), + } + } else { + match size { + 1 => write!(fmt, "{}", raw as u8)?, + 2 => write!(fmt, "{}", raw as u16)?, + 4 => write!(fmt, "{}", raw as u32)?, + 8 => write!(fmt, "{}", raw as u64)?, + 16 => write!(fmt, "{}", raw as u128)?, + _ => bug!("ConstInt 0x{:x} with size = {} and signed = {}", raw, size, signed), + } + if fmt.alternate() { + match (size, is_ptr_sized_integral) { + (_, true) => write!(fmt, "_usize")?, + (1, _) => write!(fmt, "_u8")?, + (2, _) => write!(fmt, "_u16")?, + (4, _) => write!(fmt, "_u32")?, + (8, _) => write!(fmt, "_u64")?, + (16, _) => write!(fmt, "_u128")?, + _ => bug!(), + } + } + Ok(()) + } + } + } +} + +/// The raw bytes of a simple value. +/// +/// This is a packed struct in order to allow this type to be optimally embedded in enums +/// (like Scalar). +#[derive(Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)] +#[repr(packed)] +pub struct ScalarInt { + /// The first `size` bytes of `data` are the value. + /// Do not try to read less or more bytes than that. The remaining bytes must be 0. + data: u128, + size: NonZeroU8, +} + +// Cannot derive these, as the derives take references to the fields, and we +// can't take references to fields of packed structs. +impl<CTX> crate::ty::HashStable<CTX> for ScalarInt { + fn hash_stable(&self, hcx: &mut CTX, hasher: &mut crate::ty::StableHasher) { + // Using a block `{self.data}` here to force a copy instead of using `self.data` + // directly, because `hash_stable` takes `&self` and would thus borrow `self.data`. + // Since `Self` is a packed struct, that would create a possibly unaligned reference, + // which is UB. + { self.data }.hash_stable(hcx, hasher); + self.size.get().hash_stable(hcx, hasher); + } +} + +impl<S: Encoder> Encodable<S> for ScalarInt { + fn encode(&self, s: &mut S) { + s.emit_u128(self.data); + s.emit_u8(self.size.get()); + } +} + +impl<D: Decoder> Decodable<D> for ScalarInt { + fn decode(d: &mut D) -> ScalarInt { + ScalarInt { data: d.read_u128(), size: NonZeroU8::new(d.read_u8()).unwrap() } + } +} + +impl ScalarInt { + pub const TRUE: ScalarInt = ScalarInt { data: 1_u128, size: NonZeroU8::new(1).unwrap() }; + + pub const FALSE: ScalarInt = ScalarInt { data: 0_u128, size: NonZeroU8::new(1).unwrap() }; + + #[inline] + pub fn size(self) -> Size { + Size::from_bytes(self.size.get()) + } + + /// Make sure the `data` fits in `size`. + /// This is guaranteed by all constructors here, but having had this check saved us from + /// bugs many times in the past, so keeping it around is definitely worth it. + #[inline(always)] + fn check_data(self) { + // Using a block `{self.data}` here to force a copy instead of using `self.data` + // directly, because `debug_assert_eq` takes references to its arguments and formatting + // arguments and would thus borrow `self.data`. Since `Self` + // is a packed struct, that would create a possibly unaligned reference, which + // is UB. + debug_assert_eq!( + self.size().truncate(self.data), + { self.data }, + "Scalar value {:#x} exceeds size of {} bytes", + { self.data }, + self.size + ); + } + + #[inline] + pub fn null(size: Size) -> Self { + Self { data: 0, size: NonZeroU8::new(size.bytes() as u8).unwrap() } + } + + #[inline] + pub fn is_null(self) -> bool { + self.data == 0 + } + + #[inline] + pub fn try_from_uint(i: impl Into<u128>, size: Size) -> Option<Self> { + let data = i.into(); + if size.truncate(data) == data { + Some(Self { data, size: NonZeroU8::new(size.bytes() as u8).unwrap() }) + } else { + None + } + } + + #[inline] + pub fn try_from_int(i: impl Into<i128>, size: Size) -> Option<Self> { + let i = i.into(); + // `into` performed sign extension, we have to truncate + let truncated = size.truncate(i as u128); + if size.sign_extend(truncated) as i128 == i { + Some(Self { data: truncated, size: NonZeroU8::new(size.bytes() as u8).unwrap() }) + } else { + None + } + } + + #[inline] + pub fn assert_bits(self, target_size: Size) -> u128 { + self.to_bits(target_size).unwrap_or_else(|size| { + bug!("expected int of size {}, but got size {}", target_size.bytes(), size.bytes()) + }) + } + + #[inline] + pub fn to_bits(self, target_size: Size) -> Result<u128, Size> { + assert_ne!(target_size.bytes(), 0, "you should never look at the bits of a ZST"); + if target_size.bytes() == u64::from(self.size.get()) { + self.check_data(); + Ok(self.data) + } else { + Err(self.size()) + } + } + + #[inline] + pub fn try_to_machine_usize<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Result<u64, Size> { + Ok(self.to_bits(tcx.data_layout.pointer_size)? as u64) + } + + /// Tries to convert the `ScalarInt` to an unsigned integer of the given size. + /// Fails if the size of the `ScalarInt` is unequal to `size` and returns the + /// `ScalarInt`s size in that case. + #[inline] + pub fn try_to_uint(self, size: Size) -> Result<u128, Size> { + self.to_bits(size) + } + + // Tries to convert the `ScalarInt` to `u8`. Fails if the `size` of the `ScalarInt` + // in not equal to `Size { raw: 1 }` and returns the `size` value of the `ScalarInt` in + // that case. + #[inline] + pub fn try_to_u8(self) -> Result<u8, Size> { + self.to_bits(Size::from_bits(8)).map(|v| u8::try_from(v).unwrap()) + } + + /// Tries to convert the `ScalarInt` to `u16`. Fails if the size of the `ScalarInt` + /// in not equal to `Size { raw: 2 }` and returns the `size` value of the `ScalarInt` in + /// that case. + #[inline] + pub fn try_to_u16(self) -> Result<u16, Size> { + self.to_bits(Size::from_bits(16)).map(|v| u16::try_from(v).unwrap()) + } + + /// Tries to convert the `ScalarInt` to `u32`. Fails if the `size` of the `ScalarInt` + /// in not equal to `Size { raw: 4 }` and returns the `size` value of the `ScalarInt` in + /// that case. + #[inline] + pub fn try_to_u32(self) -> Result<u32, Size> { + self.to_bits(Size::from_bits(32)).map(|v| u32::try_from(v).unwrap()) + } + + /// Tries to convert the `ScalarInt` to `u64`. Fails if the `size` of the `ScalarInt` + /// in not equal to `Size { raw: 8 }` and returns the `size` value of the `ScalarInt` in + /// that case. + #[inline] + pub fn try_to_u64(self) -> Result<u64, Size> { + self.to_bits(Size::from_bits(64)).map(|v| u64::try_from(v).unwrap()) + } + + /// Tries to convert the `ScalarInt` to `u128`. Fails if the `size` of the `ScalarInt` + /// in not equal to `Size { raw: 16 }` and returns the `size` value of the `ScalarInt` in + /// that case. + #[inline] + pub fn try_to_u128(self) -> Result<u128, Size> { + self.to_bits(Size::from_bits(128)) + } + + /// Tries to convert the `ScalarInt` to a signed integer of the given size. + /// Fails if the size of the `ScalarInt` is unequal to `size` and returns the + /// `ScalarInt`s size in that case. + #[inline] + pub fn try_to_int(self, size: Size) -> Result<i128, Size> { + let b = self.to_bits(size)?; + Ok(size.sign_extend(b) as i128) + } + + /// Tries to convert the `ScalarInt` to i8. + /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 1 }` + /// and returns the `ScalarInt`s size in that case. + pub fn try_to_i8(self) -> Result<i8, Size> { + self.try_to_int(Size::from_bits(8)).map(|v| i8::try_from(v).unwrap()) + } + + /// Tries to convert the `ScalarInt` to i16. + /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 2 }` + /// and returns the `ScalarInt`s size in that case. + pub fn try_to_i16(self) -> Result<i16, Size> { + self.try_to_int(Size::from_bits(16)).map(|v| i16::try_from(v).unwrap()) + } + + /// Tries to convert the `ScalarInt` to i32. + /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 4 }` + /// and returns the `ScalarInt`s size in that case. + pub fn try_to_i32(self) -> Result<i32, Size> { + self.try_to_int(Size::from_bits(32)).map(|v| i32::try_from(v).unwrap()) + } + + /// Tries to convert the `ScalarInt` to i64. + /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 8 }` + /// and returns the `ScalarInt`s size in that case. + pub fn try_to_i64(self) -> Result<i64, Size> { + self.try_to_int(Size::from_bits(64)).map(|v| i64::try_from(v).unwrap()) + } + + /// Tries to convert the `ScalarInt` to i128. + /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 16 }` + /// and returns the `ScalarInt`s size in that case. + pub fn try_to_i128(self) -> Result<i128, Size> { + self.try_to_int(Size::from_bits(128)).map(|v| i128::try_from(v).unwrap()) + } +} + +macro_rules! from { + ($($ty:ty),*) => { + $( + impl From<$ty> for ScalarInt { + #[inline] + fn from(u: $ty) -> Self { + Self { + data: u128::from(u), + size: NonZeroU8::new(std::mem::size_of::<$ty>() as u8).unwrap(), + } + } + } + )* + } +} + +macro_rules! try_from { + ($($ty:ty),*) => { + $( + impl TryFrom<ScalarInt> for $ty { + type Error = Size; + #[inline] + fn try_from(int: ScalarInt) -> Result<Self, Size> { + // The `unwrap` cannot fail because to_bits (if it succeeds) + // is guaranteed to return a value that fits into the size. + int.to_bits(Size::from_bytes(std::mem::size_of::<$ty>())) + .map(|u| u.try_into().unwrap()) + } + } + )* + } +} + +from!(u8, u16, u32, u64, u128, bool); +try_from!(u8, u16, u32, u64, u128); + +impl TryFrom<ScalarInt> for bool { + type Error = Size; + #[inline] + fn try_from(int: ScalarInt) -> Result<Self, Size> { + int.to_bits(Size::from_bytes(1)).and_then(|u| match u { + 0 => Ok(false), + 1 => Ok(true), + _ => Err(Size::from_bytes(1)), + }) + } +} + +impl From<char> for ScalarInt { + #[inline] + fn from(c: char) -> Self { + Self { data: c as u128, size: NonZeroU8::new(std::mem::size_of::<char>() as u8).unwrap() } + } +} + +/// Error returned when a conversion from ScalarInt to char fails. +#[derive(Debug)] +pub struct CharTryFromScalarInt; + +impl TryFrom<ScalarInt> for char { + type Error = CharTryFromScalarInt; + + #[inline] + fn try_from(int: ScalarInt) -> Result<Self, Self::Error> { + let Ok(bits) = int.to_bits(Size::from_bytes(std::mem::size_of::<char>())) else { + return Err(CharTryFromScalarInt); + }; + match char::from_u32(bits.try_into().unwrap()) { + Some(c) => Ok(c), + None => Err(CharTryFromScalarInt), + } + } +} + +impl From<Single> for ScalarInt { + #[inline] + fn from(f: Single) -> Self { + // We trust apfloat to give us properly truncated data. + Self { data: f.to_bits(), size: NonZeroU8::new((Single::BITS / 8) as u8).unwrap() } + } +} + +impl TryFrom<ScalarInt> for Single { + type Error = Size; + #[inline] + fn try_from(int: ScalarInt) -> Result<Self, Size> { + int.to_bits(Size::from_bytes(4)).map(Self::from_bits) + } +} + +impl From<Double> for ScalarInt { + #[inline] + fn from(f: Double) -> Self { + // We trust apfloat to give us properly truncated data. + Self { data: f.to_bits(), size: NonZeroU8::new((Double::BITS / 8) as u8).unwrap() } + } +} + +impl TryFrom<ScalarInt> for Double { + type Error = Size; + #[inline] + fn try_from(int: ScalarInt) -> Result<Self, Size> { + int.to_bits(Size::from_bytes(8)).map(Self::from_bits) + } +} + +impl fmt::Debug for ScalarInt { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + // Dispatch to LowerHex below. + write!(f, "0x{:x}", self) + } +} + +impl fmt::LowerHex for ScalarInt { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + self.check_data(); + if f.alternate() { + // Like regular ints, alternate flag adds leading `0x`. + write!(f, "0x")?; + } + // Format as hex number wide enough to fit any value of the given `size`. + // So data=20, size=1 will be "0x14", but with size=4 it'll be "0x00000014". + // Using a block `{self.data}` here to force a copy instead of using `self.data` + // directly, because `write!` takes references to its formatting arguments and + // would thus borrow `self.data`. Since `Self` + // is a packed struct, that would create a possibly unaligned reference, which + // is UB. + write!(f, "{:01$x}", { self.data }, self.size.get() as usize * 2) + } +} + +impl fmt::UpperHex for ScalarInt { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + self.check_data(); + // Format as hex number wide enough to fit any value of the given `size`. + // So data=20, size=1 will be "0x14", but with size=4 it'll be "0x00000014". + // Using a block `{self.data}` here to force a copy instead of using `self.data` + // directly, because `write!` takes references to its formatting arguments and + // would thus borrow `self.data`. Since `Self` + // is a packed struct, that would create a possibly unaligned reference, which + // is UB. + write!(f, "{:01$X}", { self.data }, self.size.get() as usize * 2) + } +} + +impl fmt::Display for ScalarInt { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + self.check_data(); + write!(f, "{}", { self.data }) + } +} diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs new file mode 100644 index 000000000..cb0137d2e --- /dev/null +++ b/compiler/rustc_middle/src/ty/consts/kind.rs @@ -0,0 +1,239 @@ +use std::convert::TryInto; + +use crate::mir::interpret::{AllocId, ConstValue, Scalar}; +use crate::mir::Promoted; +use crate::ty::subst::{InternalSubsts, SubstsRef}; +use crate::ty::ParamEnv; +use crate::ty::{self, TyCtxt, TypeVisitable}; +use rustc_errors::ErrorGuaranteed; +use rustc_hir::def_id::DefId; +use rustc_macros::HashStable; +use rustc_target::abi::Size; + +use super::ScalarInt; +/// An unevaluated, potentially generic, constant. +#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Lift)] +#[derive(Hash, HashStable)] +pub struct Unevaluated<'tcx, P = Option<Promoted>> { + pub def: ty::WithOptConstParam<DefId>, + pub substs: SubstsRef<'tcx>, + pub promoted: P, +} + +impl<'tcx> Unevaluated<'tcx> { + #[inline] + pub fn shrink(self) -> Unevaluated<'tcx, ()> { + debug_assert_eq!(self.promoted, None); + Unevaluated { def: self.def, substs: self.substs, promoted: () } + } +} + +impl<'tcx> Unevaluated<'tcx, ()> { + #[inline] + pub fn expand(self) -> Unevaluated<'tcx> { + Unevaluated { def: self.def, substs: self.substs, promoted: None } + } +} + +impl<'tcx, P: Default> Unevaluated<'tcx, P> { + #[inline] + pub fn new(def: ty::WithOptConstParam<DefId>, substs: SubstsRef<'tcx>) -> Unevaluated<'tcx, P> { + Unevaluated { def, substs, promoted: Default::default() } + } +} + +/// Represents a constant in Rust. +#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable)] +#[derive(Hash, HashStable)] +pub enum ConstKind<'tcx> { + /// A const generic parameter. + Param(ty::ParamConst), + + /// Infer the value of the const. + Infer(InferConst<'tcx>), + + /// Bound const variable, used only when preparing a trait query. + Bound(ty::DebruijnIndex, ty::BoundVar), + + /// A placeholder const - universally quantified higher-ranked const. + Placeholder(ty::PlaceholderConst<'tcx>), + + /// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other + /// variants when the code is monomorphic enough for that. + Unevaluated(Unevaluated<'tcx>), + + /// Used to hold computed value. + Value(ty::ValTree<'tcx>), + + /// A placeholder for a const which could not be computed; this is + /// propagated to avoid useless error messages. + Error(ty::DelaySpanBugEmitted), +} + +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +static_assert_size!(ConstKind<'_>, 40); + +impl<'tcx> ConstKind<'tcx> { + #[inline] + pub fn try_to_value(self) -> Option<ty::ValTree<'tcx>> { + if let ConstKind::Value(val) = self { Some(val) } else { None } + } + + #[inline] + pub fn try_to_scalar(self) -> Option<Scalar<AllocId>> { + self.try_to_value()?.try_to_scalar() + } + + #[inline] + pub fn try_to_scalar_int(self) -> Option<ScalarInt> { + self.try_to_value()?.try_to_scalar_int() + } + + #[inline] + pub fn try_to_bits(self, size: Size) -> Option<u128> { + self.try_to_scalar_int()?.to_bits(size).ok() + } + + #[inline] + pub fn try_to_bool(self) -> Option<bool> { + self.try_to_scalar_int()?.try_into().ok() + } + + #[inline] + pub fn try_to_machine_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> { + self.try_to_value()?.try_to_machine_usize(tcx) + } +} + +/// An inference variable for a const, for use in const generics. +#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Hash)] +#[derive(HashStable)] +pub enum InferConst<'tcx> { + /// Infer the value of the const. + Var(ty::ConstVid<'tcx>), + /// A fresh const variable. See `infer::freshen` for more details. + Fresh(u32), +} + +enum EvalMode { + Typeck, + Mir, +} + +enum EvalResult<'tcx> { + ValTree(ty::ValTree<'tcx>), + ConstVal(ConstValue<'tcx>), +} + +impl<'tcx> ConstKind<'tcx> { + #[inline] + /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the + /// unevaluated constant. + pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Self { + self.try_eval_for_typeck(tcx, param_env).and_then(Result::ok).map_or(self, ConstKind::Value) + } + + #[inline] + /// Tries to evaluate the constant if it is `Unevaluated`. If that isn't possible or necessary + /// return `None`. + // FIXME(@lcnr): Completely rework the evaluation/normalization system for `ty::Const` once valtrees are merged. + pub fn try_eval_for_mir( + self, + tcx: TyCtxt<'tcx>, + param_env: ParamEnv<'tcx>, + ) -> Option<Result<ConstValue<'tcx>, ErrorGuaranteed>> { + match self.try_eval_inner(tcx, param_env, EvalMode::Mir) { + Some(Ok(EvalResult::ValTree(_))) => unreachable!(), + Some(Ok(EvalResult::ConstVal(v))) => Some(Ok(v)), + Some(Err(e)) => Some(Err(e)), + None => None, + } + } + + #[inline] + /// Tries to evaluate the constant if it is `Unevaluated`. If that isn't possible or necessary + /// return `None`. + // FIXME(@lcnr): Completely rework the evaluation/normalization system for `ty::Const` once valtrees are merged. + pub fn try_eval_for_typeck( + self, + tcx: TyCtxt<'tcx>, + param_env: ParamEnv<'tcx>, + ) -> Option<Result<ty::ValTree<'tcx>, ErrorGuaranteed>> { + match self.try_eval_inner(tcx, param_env, EvalMode::Typeck) { + Some(Ok(EvalResult::ValTree(v))) => Some(Ok(v)), + Some(Ok(EvalResult::ConstVal(_))) => unreachable!(), + Some(Err(e)) => Some(Err(e)), + None => None, + } + } + + #[inline] + fn try_eval_inner( + self, + tcx: TyCtxt<'tcx>, + param_env: ParamEnv<'tcx>, + eval_mode: EvalMode, + ) -> Option<Result<EvalResult<'tcx>, ErrorGuaranteed>> { + if let ConstKind::Unevaluated(unevaluated) = self { + use crate::mir::interpret::ErrorHandled; + + // HACK(eddyb) this erases lifetimes even though `const_eval_resolve` + // also does later, but we want to do it before checking for + // inference variables. + // Note that we erase regions *before* calling `with_reveal_all_normalized`, + // so that we don't try to invoke this query with + // any region variables. + let param_env_and = tcx + .erase_regions(param_env) + .with_reveal_all_normalized(tcx) + .and(tcx.erase_regions(unevaluated)); + + // HACK(eddyb) when the query key would contain inference variables, + // attempt using identity substs and `ParamEnv` instead, that will succeed + // when the expression doesn't depend on any parameters. + // FIXME(eddyb, skinny121) pass `InferCtxt` into here when it's available, so that + // we can call `infcx.const_eval_resolve` which handles inference variables. + let param_env_and = if param_env_and.needs_infer() { + tcx.param_env(unevaluated.def.did).and(ty::Unevaluated { + def: unevaluated.def, + substs: InternalSubsts::identity_for_item(tcx, unevaluated.def.did), + promoted: unevaluated.promoted, + }) + } else { + param_env_and + }; + + // FIXME(eddyb) maybe the `const_eval_*` methods should take + // `ty::ParamEnvAnd` instead of having them separate. + let (param_env, unevaluated) = param_env_and.into_parts(); + // try to resolve e.g. associated constants to their definition on an impl, and then + // evaluate the const. + match eval_mode { + EvalMode::Typeck => { + match tcx.const_eval_resolve_for_typeck(param_env, unevaluated, None) { + // NOTE(eddyb) `val` contains no lifetimes/types/consts, + // and we use the original type, so nothing from `substs` + // (which may be identity substs, see above), + // can leak through `val` into the const we return. + Ok(val) => Some(Ok(EvalResult::ValTree(val?))), + Err(ErrorHandled::TooGeneric | ErrorHandled::Linted) => None, + Err(ErrorHandled::Reported(e)) => Some(Err(e)), + } + } + EvalMode::Mir => { + match tcx.const_eval_resolve(param_env, unevaluated, None) { + // NOTE(eddyb) `val` contains no lifetimes/types/consts, + // and we use the original type, so nothing from `substs` + // (which may be identity substs, see above), + // can leak through `val` into the const we return. + Ok(val) => Some(Ok(EvalResult::ConstVal(val))), + Err(ErrorHandled::TooGeneric | ErrorHandled::Linted) => None, + Err(ErrorHandled::Reported(e)) => Some(Err(e)), + } + } + } + } else { + None + } + } +} diff --git a/compiler/rustc_middle/src/ty/consts/valtree.rs b/compiler/rustc_middle/src/ty/consts/valtree.rs new file mode 100644 index 000000000..93707bb18 --- /dev/null +++ b/compiler/rustc_middle/src/ty/consts/valtree.rs @@ -0,0 +1,104 @@ +use super::ScalarInt; +use crate::mir::interpret::{AllocId, Scalar}; +use crate::ty::{self, Ty, TyCtxt}; +use rustc_macros::{HashStable, TyDecodable, TyEncodable}; + +#[derive(Copy, Clone, Debug, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)] +#[derive(HashStable)] +/// This datastructure is used to represent the value of constants used in the type system. +/// +/// We explicitly choose a different datastructure from the way values are processed within +/// CTFE, as in the type system equal values (according to their `PartialEq`) must also have +/// equal representation (`==` on the rustc data structure, e.g. `ValTree`) and vice versa. +/// Since CTFE uses `AllocId` to represent pointers, it often happens that two different +/// `AllocId`s point to equal values. So we may end up with different representations for +/// two constants whose value is `&42`. Furthermore any kind of struct that has padding will +/// have arbitrary values within that padding, even if the values of the struct are the same. +/// +/// `ValTree` does not have this problem with representation, as it only contains integers or +/// lists of (nested) `ValTree`. +pub enum ValTree<'tcx> { + /// ZSTs, integers, `bool`, `char` are represented as scalars. + /// See the `ScalarInt` documentation for how `ScalarInt` guarantees that equal values + /// of these types have the same representation. + Leaf(ScalarInt), + + //SliceOrStr(ValSlice<'tcx>), + // dont use SliceOrStr for now + /// The fields of any kind of aggregate. Structs, tuples and arrays are represented by + /// listing their fields' values in order. + /// Enums are represented by storing their discriminant as a field, followed by all + /// the fields of the variant. + Branch(&'tcx [ValTree<'tcx>]), +} + +impl<'tcx> ValTree<'tcx> { + pub fn zst() -> Self { + Self::Branch(&[]) + } + + #[inline] + pub fn unwrap_leaf(self) -> ScalarInt { + match self { + Self::Leaf(s) => s, + _ => bug!("expected leaf, got {:?}", self), + } + } + + #[inline] + pub fn unwrap_branch(self) -> &'tcx [Self] { + match self { + Self::Branch(branch) => branch, + _ => bug!("expected branch, got {:?}", self), + } + } + + pub fn from_raw_bytes<'a>(tcx: TyCtxt<'tcx>, bytes: &'a [u8]) -> Self { + let branches = bytes.iter().map(|b| Self::Leaf(ScalarInt::from(*b))); + let interned = tcx.arena.alloc_from_iter(branches); + + Self::Branch(interned) + } + + pub fn from_scalar_int(i: ScalarInt) -> Self { + Self::Leaf(i) + } + + pub fn try_to_scalar(self) -> Option<Scalar<AllocId>> { + self.try_to_scalar_int().map(Scalar::Int) + } + + pub fn try_to_scalar_int(self) -> Option<ScalarInt> { + match self { + Self::Leaf(s) => Some(s), + Self::Branch(_) => None, + } + } + + pub fn try_to_machine_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> { + self.try_to_scalar_int().map(|s| s.try_to_machine_usize(tcx).ok()).flatten() + } + + /// Get the values inside the ValTree as a slice of bytes. This only works for + /// constants with types &str, &[u8], or [u8; _]. + pub fn try_to_raw_bytes(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<&'tcx [u8]> { + match ty.kind() { + ty::Ref(_, inner_ty, _) => match inner_ty.kind() { + // `&str` can be interpreted as raw bytes + ty::Str => {} + // `&[u8]` can be interpreted as raw bytes + ty::Slice(slice_ty) if *slice_ty == tcx.types.u8 => {} + // other `&_` can't be interpreted as raw bytes + _ => return None, + }, + // `[u8; N]` can be interpreted as raw bytes + ty::Array(array_ty, _) if *array_ty == tcx.types.u8 => {} + // Otherwise, type cannot be interpreted as raw bytes + _ => return None, + } + + Some(tcx.arena.alloc_from_iter( + self.unwrap_branch().into_iter().map(|v| v.unwrap_leaf().try_to_u8().unwrap()), + )) + } +} |