| use std::fmt::{self, Debug, Display, Formatter}; |
| |
| use rustc_hir::def_id::DefId; |
| use rustc_session::{config::RemapPathScopeComponents, RemapFileNameExt}; |
| use rustc_span::{Span, DUMMY_SP}; |
| use rustc_target::abi::{HasDataLayout, Size}; |
| |
| use crate::mir::interpret::{alloc_range, AllocId, ConstAllocation, ErrorHandled, Scalar}; |
| use crate::mir::{pretty_print_const_value, Promoted}; |
| use crate::ty::print::with_no_trimmed_paths; |
| use crate::ty::GenericArgsRef; |
| use crate::ty::ScalarInt; |
| use crate::ty::{self, print::pretty_print_const, Ty, TyCtxt}; |
| |
| /////////////////////////////////////////////////////////////////////////// |
| /// Evaluated Constants |
| |
| /// Represents the result of const evaluation via the `eval_to_allocation` query. |
| /// Not to be confused with `ConstAllocation`, which directly refers to the underlying data! |
| /// Here we indirect via an `AllocId`. |
| #[derive(Copy, Clone, HashStable, TyEncodable, TyDecodable, Debug, Hash, Eq, PartialEq)] |
| pub struct ConstAlloc<'tcx> { |
| /// The value lives here, at offset 0, and that allocation definitely is an `AllocKind::Memory` |
| /// (so you can use `AllocMap::unwrap_memory`). |
| pub alloc_id: AllocId, |
| pub ty: Ty<'tcx>, |
| } |
| |
| /// Represents a constant value in Rust. `Scalar` and `Slice` are optimizations for |
| /// array length computations, enum discriminants and the pattern matching logic. |
| #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash)] |
| #[derive(HashStable, Lift)] |
| pub enum ConstValue<'tcx> { |
| /// Used for types with `layout::abi::Scalar` ABI. |
| /// |
| /// Not using the enum `Value` to encode that this must not be `Uninit`. |
| Scalar(Scalar), |
| |
| /// Only for ZSTs. |
| ZeroSized, |
| |
| /// Used for references to unsized types with slice tail. |
| /// |
| /// This is worth an optimized representation since Rust has literals of type `&str` and |
| /// `&[u8]`. Not having to indirect those through an `AllocId` (or two, if we used `Indirect`) |
| /// has shown measurable performance improvements on stress tests. We then reuse this |
| /// optimization for slice-tail types more generally during valtree-to-constval conversion. |
| Slice { |
| /// The allocation storing the slice contents. |
| /// This always points to the beginning of the allocation. |
| data: ConstAllocation<'tcx>, |
| /// The metadata field of the reference. |
| /// This is a "target usize", so we use `u64` as in the interpreter. |
| meta: u64, |
| }, |
| |
| /// A value not representable by the other variants; needs to be stored in-memory. |
| /// |
| /// Must *not* be used for scalars or ZST, but having `&str` or other slices in this variant is fine. |
| Indirect { |
| /// The backing memory of the value. May contain more memory than needed for just the value |
| /// if this points into some other larger ConstValue. |
| /// |
| /// We use an `AllocId` here instead of a `ConstAllocation<'tcx>` to make sure that when a |
| /// raw constant (which is basically just an `AllocId`) is turned into a `ConstValue` and |
| /// back, we can preserve the original `AllocId`. |
| alloc_id: AllocId, |
| /// Offset into `alloc` |
| offset: Size, |
| }, |
| } |
| |
| #[cfg(all(any(target_arch = "x86_64", target_arch = "aarch64"), target_pointer_width = "64"))] |
| static_assert_size!(ConstValue<'_>, 24); |
| |
| impl<'tcx> ConstValue<'tcx> { |
| #[inline] |
| pub fn try_to_scalar(&self) -> Option<Scalar> { |
| match *self { |
| ConstValue::Indirect { .. } | ConstValue::Slice { .. } | ConstValue::ZeroSized => None, |
| ConstValue::Scalar(val) => Some(val), |
| } |
| } |
| |
| pub fn try_to_scalar_int(&self) -> Option<ScalarInt> { |
| self.try_to_scalar()?.try_to_int().ok() |
| } |
| |
| pub fn try_to_bits(&self, size: Size) -> Option<u128> { |
| self.try_to_scalar_int()?.to_bits(size).ok() |
| } |
| |
| pub fn try_to_bool(&self) -> Option<bool> { |
| self.try_to_scalar_int()?.try_into().ok() |
| } |
| |
| pub fn try_to_target_usize(&self, tcx: TyCtxt<'tcx>) -> Option<u64> { |
| self.try_to_scalar_int()?.try_to_target_usize(tcx).ok() |
| } |
| |
| pub fn try_to_bits_for_ty( |
| &self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ty: Ty<'tcx>, |
| ) -> Option<u128> { |
| let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size; |
| self.try_to_bits(size) |
| } |
| |
| pub fn from_bool(b: bool) -> Self { |
| ConstValue::Scalar(Scalar::from_bool(b)) |
| } |
| |
| pub fn from_u64(i: u64) -> Self { |
| ConstValue::Scalar(Scalar::from_u64(i)) |
| } |
| |
| pub fn from_u128(i: u128) -> Self { |
| ConstValue::Scalar(Scalar::from_u128(i)) |
| } |
| |
| pub fn from_target_usize(i: u64, cx: &impl HasDataLayout) -> Self { |
| ConstValue::Scalar(Scalar::from_target_usize(i, cx)) |
| } |
| |
| /// Must only be called on constants of type `&str` or `&[u8]`! |
| pub fn try_get_slice_bytes_for_diagnostics(&self, tcx: TyCtxt<'tcx>) -> Option<&'tcx [u8]> { |
| let (data, start, end) = match self { |
| ConstValue::Scalar(_) | ConstValue::ZeroSized => { |
| bug!("`try_get_slice_bytes` on non-slice constant") |
| } |
| &ConstValue::Slice { data, meta } => (data, 0, meta), |
| &ConstValue::Indirect { alloc_id, offset } => { |
| // The reference itself is stored behind an indirection. |
| // Load the reference, and then load the actual slice contents. |
| let a = tcx.global_alloc(alloc_id).unwrap_memory().inner(); |
| let ptr_size = tcx.data_layout.pointer_size; |
| if a.size() < offset + 2 * ptr_size { |
| // (partially) dangling reference |
| return None; |
| } |
| // Read the wide pointer components. |
| let ptr = a |
| .read_scalar( |
| &tcx, |
| alloc_range(offset, ptr_size), |
| /* read_provenance */ true, |
| ) |
| .ok()?; |
| let ptr = ptr.to_pointer(&tcx).ok()?; |
| let len = a |
| .read_scalar( |
| &tcx, |
| alloc_range(offset + ptr_size, ptr_size), |
| /* read_provenance */ false, |
| ) |
| .ok()?; |
| let len = len.to_target_usize(&tcx).ok()?; |
| if len == 0 { |
| return Some(&[]); |
| } |
| // Non-empty slice, must have memory. We know this is a relative pointer. |
| let (inner_prov, offset) = ptr.into_parts(); |
| let data = tcx.global_alloc(inner_prov?.alloc_id()).unwrap_memory(); |
| (data, offset.bytes(), offset.bytes() + len) |
| } |
| }; |
| |
| // This is for diagnostics only, so we are okay to use `inspect_with_uninit_and_ptr_outside_interpreter`. |
| let start = start.try_into().unwrap(); |
| let end = end.try_into().unwrap(); |
| Some(data.inner().inspect_with_uninit_and_ptr_outside_interpreter(start..end)) |
| } |
| |
| /// Check if a constant may contain provenance information. This is used by MIR opts. |
| /// Can return `true` even if there is no provenance. |
| pub fn may_have_provenance(&self, tcx: TyCtxt<'tcx>, size: Size) -> bool { |
| match *self { |
| ConstValue::ZeroSized | ConstValue::Scalar(Scalar::Int(_)) => return false, |
| ConstValue::Scalar(Scalar::Ptr(..)) => return true, |
| // It's hard to find out the part of the allocation we point to; |
| // just conservatively check everything. |
| ConstValue::Slice { data, meta: _ } => !data.inner().provenance().ptrs().is_empty(), |
| ConstValue::Indirect { alloc_id, offset } => !tcx |
| .global_alloc(alloc_id) |
| .unwrap_memory() |
| .inner() |
| .provenance() |
| .range_empty(super::AllocRange::from(offset..offset + size), &tcx), |
| } |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| /// Constants |
| |
| #[derive(Clone, Copy, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable, Debug)] |
| #[derive(TypeFoldable, TypeVisitable, Lift)] |
| pub enum Const<'tcx> { |
| /// This constant came from the type system. |
| /// |
| /// Any way of turning `ty::Const` into `ConstValue` should go through `valtree_to_const_val`; |
| /// this ensures that we consistently produce "clean" values without data in the padding or |
| /// anything like that. |
| Ty(ty::Const<'tcx>), |
| |
| /// An unevaluated mir constant which is not part of the type system. |
| /// |
| /// Note that `Ty(ty::ConstKind::Unevaluated)` and this variant are *not* identical! `Ty` will |
| /// always flow through a valtree, so all data not captured in the valtree is lost. This variant |
| /// directly uses the evaluated result of the given constant, including e.g. data stored in |
| /// padding. |
| Unevaluated(UnevaluatedConst<'tcx>, Ty<'tcx>), |
| |
| /// This constant cannot go back into the type system, as it represents |
| /// something the type system cannot handle (e.g. pointers). |
| Val(ConstValue<'tcx>, Ty<'tcx>), |
| } |
| |
| impl<'tcx> Const<'tcx> { |
| pub fn identity_unevaluated(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::EarlyBinder<Const<'tcx>> { |
| ty::EarlyBinder::bind(Const::Unevaluated( |
| UnevaluatedConst { |
| def: def_id, |
| args: ty::GenericArgs::identity_for_item(tcx, def_id), |
| promoted: None, |
| }, |
| tcx.type_of(def_id).skip_binder(), |
| )) |
| } |
| |
| #[inline(always)] |
| pub fn ty(&self) -> Ty<'tcx> { |
| match self { |
| Const::Ty(c) => c.ty(), |
| Const::Val(_, ty) | Const::Unevaluated(_, ty) => *ty, |
| } |
| } |
| |
| #[inline] |
| pub fn try_to_scalar(self) -> Option<Scalar> { |
| match self { |
| Const::Ty(c) => match c.kind() { |
| ty::ConstKind::Value(valtree) if c.ty().is_primitive() => { |
| // A valtree of a type where leaves directly represent the scalar const value. |
| Some(valtree.unwrap_leaf().into()) |
| } |
| _ => None, |
| }, |
| Const::Val(val, _) => val.try_to_scalar(), |
| Const::Unevaluated(..) => None, |
| } |
| } |
| |
| #[inline] |
| pub fn try_to_scalar_int(self) -> Option<ScalarInt> { |
| self.try_to_scalar()?.try_to_int().ok() |
| } |
| |
| #[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 eval( |
| self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| span: Span, |
| ) -> Result<ConstValue<'tcx>, ErrorHandled> { |
| match self { |
| Const::Ty(c) => { |
| // We want to consistently have a "clean" value for type system constants (i.e., no |
| // data hidden in the padding), so we always go through a valtree here. |
| let val = c.eval(tcx, param_env, span)?; |
| Ok(tcx.valtree_to_const_val((self.ty(), val))) |
| } |
| Const::Unevaluated(uneval, _) => { |
| // FIXME: We might want to have a `try_eval`-like function on `Unevaluated` |
| tcx.const_eval_resolve(param_env, uneval, span) |
| } |
| Const::Val(val, _) => Ok(val), |
| } |
| } |
| |
| /// Normalizes the constant to a value or an error if possible. |
| #[inline] |
| pub fn normalize(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self { |
| match self.eval(tcx, param_env, DUMMY_SP) { |
| Ok(val) => Self::Val(val, self.ty()), |
| Err(ErrorHandled::Reported(guar, _span)) => { |
| Self::Ty(ty::Const::new_error(tcx, guar.into(), self.ty())) |
| } |
| Err(ErrorHandled::TooGeneric(_span)) => self, |
| } |
| } |
| |
| #[inline] |
| pub fn try_eval_scalar( |
| self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> Option<Scalar> { |
| match self { |
| Const::Ty(c) if c.ty().is_primitive() => { |
| // Avoid the `valtree_to_const_val` query. Can only be done on primitive types that |
| // are valtree leaves, and *not* on references. (References should return the |
| // pointer here, which valtrees don't represent.) |
| let val = c.eval(tcx, param_env, DUMMY_SP).ok()?; |
| Some(val.unwrap_leaf().into()) |
| } |
| _ => self.eval(tcx, param_env, DUMMY_SP).ok()?.try_to_scalar(), |
| } |
| } |
| |
| #[inline] |
| pub fn try_eval_scalar_int( |
| self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> Option<ScalarInt> { |
| self.try_eval_scalar(tcx, param_env)?.try_to_int().ok() |
| } |
| |
| #[inline] |
| pub fn try_eval_bits(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<u128> { |
| let int = self.try_eval_scalar_int(tcx, param_env)?; |
| let size = |
| tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(self.ty())).ok()?.size; |
| int.to_bits(size).ok() |
| } |
| |
| /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type. |
| #[inline] |
| pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> u128 { |
| self.try_eval_bits(tcx, param_env) |
| .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", self.ty(), self)) |
| } |
| |
| #[inline] |
| pub fn try_eval_target_usize( |
| self, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> Option<u64> { |
| self.try_eval_scalar_int(tcx, param_env)?.try_to_target_usize(tcx).ok() |
| } |
| |
| #[inline] |
| /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`. |
| pub fn eval_target_usize(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> u64 { |
| self.try_eval_target_usize(tcx, param_env) |
| .unwrap_or_else(|| bug!("expected usize, got {:#?}", self)) |
| } |
| |
| #[inline] |
| pub fn try_eval_bool(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<bool> { |
| self.try_eval_scalar_int(tcx, param_env)?.try_into().ok() |
| } |
| |
| #[inline] |
| pub fn from_value(val: ConstValue<'tcx>, ty: Ty<'tcx>) -> Self { |
| Self::Val(val, ty) |
| } |
| |
| pub fn from_bits( |
| tcx: TyCtxt<'tcx>, |
| bits: u128, |
| param_env_ty: ty::ParamEnvAnd<'tcx, Ty<'tcx>>, |
| ) -> Self { |
| let size = tcx |
| .layout_of(param_env_ty) |
| .unwrap_or_else(|e| { |
| bug!("could not compute layout for {:?}: {:?}", param_env_ty.value, e) |
| }) |
| .size; |
| let cv = ConstValue::Scalar(Scalar::from_uint(bits, size)); |
| |
| Self::Val(cv, param_env_ty.value) |
| } |
| |
| #[inline] |
| pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> Self { |
| let cv = ConstValue::from_bool(v); |
| Self::Val(cv, tcx.types.bool) |
| } |
| |
| #[inline] |
| pub fn zero_sized(ty: Ty<'tcx>) -> Self { |
| let cv = ConstValue::ZeroSized; |
| Self::Val(cv, ty) |
| } |
| |
| pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self { |
| let ty = tcx.types.usize; |
| Self::from_bits(tcx, n as u128, ty::ParamEnv::empty().and(ty)) |
| } |
| |
| #[inline] |
| pub fn from_scalar(_tcx: TyCtxt<'tcx>, s: Scalar, ty: Ty<'tcx>) -> Self { |
| let val = ConstValue::Scalar(s); |
| Self::Val(val, ty) |
| } |
| |
| pub fn from_ty_const(c: ty::Const<'tcx>, tcx: TyCtxt<'tcx>) -> Self { |
| match c.kind() { |
| ty::ConstKind::Value(valtree) => { |
| // Make sure that if `c` is normalized, then the return value is normalized. |
| let const_val = tcx.valtree_to_const_val((c.ty(), valtree)); |
| Self::Val(const_val, c.ty()) |
| } |
| _ => Self::Ty(c), |
| } |
| } |
| |
| /// Return true if any evaluation of this constant always returns the same value, |
| /// taking into account even pointer identity tests. |
| pub fn is_deterministic(&self) -> bool { |
| // Some constants may generate fresh allocations for pointers they contain, |
| // so using the same constant twice can yield two different results: |
| // - valtrees purposefully generate new allocations |
| // - ConstValue::Slice also generate new allocations |
| match self { |
| Const::Ty(c) => match c.kind() { |
| ty::ConstKind::Param(..) => true, |
| // A valtree may be a reference. Valtree references correspond to a |
| // different allocation each time they are evaluated. Valtrees for primitive |
| // types are fine though. |
| ty::ConstKind::Value(_) => c.ty().is_primitive(), |
| ty::ConstKind::Unevaluated(..) | ty::ConstKind::Expr(..) => false, |
| // This can happen if evaluation of a constant failed. The result does not matter |
| // much since compilation is doomed. |
| ty::ConstKind::Error(..) => false, |
| // Should not appear in runtime MIR. |
| ty::ConstKind::Infer(..) |
| | ty::ConstKind::Bound(..) |
| | ty::ConstKind::Placeholder(..) => bug!(), |
| }, |
| Const::Unevaluated(..) => false, |
| // If the same slice appears twice in the MIR, we cannot guarantee that we will |
| // give the same `AllocId` to the data. |
| Const::Val(ConstValue::Slice { .. }, _) => false, |
| Const::Val( |
| ConstValue::ZeroSized | ConstValue::Scalar(_) | ConstValue::Indirect { .. }, |
| _, |
| ) => true, |
| } |
| } |
| } |
| |
| /// An unevaluated (potentially generic) constant used in MIR. |
| #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable)] |
| #[derive(Hash, HashStable, TypeFoldable, TypeVisitable, Lift)] |
| pub struct UnevaluatedConst<'tcx> { |
| pub def: DefId, |
| pub args: GenericArgsRef<'tcx>, |
| pub promoted: Option<Promoted>, |
| } |
| |
| impl<'tcx> UnevaluatedConst<'tcx> { |
| #[inline] |
| pub fn shrink(self) -> ty::UnevaluatedConst<'tcx> { |
| assert_eq!(self.promoted, None); |
| ty::UnevaluatedConst { def: self.def, args: self.args } |
| } |
| } |
| |
| impl<'tcx> UnevaluatedConst<'tcx> { |
| #[inline] |
| pub fn new(def: DefId, args: GenericArgsRef<'tcx>) -> UnevaluatedConst<'tcx> { |
| UnevaluatedConst { def, args, promoted: Default::default() } |
| } |
| |
| #[inline] |
| pub fn from_instance(instance: ty::Instance<'tcx>) -> Self { |
| UnevaluatedConst::new(instance.def_id(), instance.args) |
| } |
| } |
| |
| impl<'tcx> Display for Const<'tcx> { |
| fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result { |
| match *self { |
| Const::Ty(c) => pretty_print_const(c, fmt, true), |
| Const::Val(val, ty) => pretty_print_const_value(val, ty, fmt), |
| // FIXME(valtrees): Correctly print mir constants. |
| Const::Unevaluated(c, _ty) => { |
| ty::tls::with(move |tcx| { |
| let c = tcx.lift(c).unwrap(); |
| // Matches `GlobalId` printing. |
| let instance = |
| with_no_trimmed_paths!(tcx.def_path_str_with_args(c.def, c.args)); |
| write!(fmt, "{instance}")?; |
| if let Some(promoted) = c.promoted { |
| write!(fmt, "::{promoted:?}")?; |
| } |
| Ok(()) |
| }) |
| } |
| } |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| /// Const-related utilities |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| pub fn span_as_caller_location(self, span: Span) -> ConstValue<'tcx> { |
| let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span); |
| let caller = self.sess.source_map().lookup_char_pos(topmost.lo()); |
| self.const_caller_location( |
| rustc_span::symbol::Symbol::intern( |
| &caller |
| .file |
| .name |
| .for_scope(self.sess, RemapPathScopeComponents::MACRO) |
| .to_string_lossy(), |
| ), |
| caller.line as u32, |
| caller.col_display as u32 + 1, |
| ) |
| } |
| } |