diff --git a/src/librustc_middle/mir/interpret/error.rs b/src/librustc_middle/mir/interpret/error.rs index d32a147344992..fc588e049d7d8 100644 --- a/src/librustc_middle/mir/interpret/error.rs +++ b/src/librustc_middle/mir/interpret/error.rs @@ -1,4 +1,4 @@ -use super::{AllocId, Pointer, RawConst, ScalarMaybeUninit}; +use super::{AllocId, Pointer, RawConst, Scalar}; use crate::mir::interpret::ConstValue; use crate::ty::layout::LayoutError; @@ -391,7 +391,7 @@ pub enum UndefinedBehaviorInfo<'tcx> { /// Using a non-character `u32` as character. InvalidChar(u32), /// An enum discriminant was set to a value which was outside the range of valid values. - InvalidDiscriminant(ScalarMaybeUninit), + InvalidDiscriminant(Scalar), /// Using a pointer-not-to-a-function as function pointer. InvalidFunctionPointer(Pointer), /// Using a string that is not valid UTF-8, diff --git a/src/librustc_middle/mir/tcx.rs b/src/librustc_middle/mir/tcx.rs index 4747aec2d5c24..4059bfedc6da4 100644 --- a/src/librustc_middle/mir/tcx.rs +++ b/src/librustc_middle/mir/tcx.rs @@ -5,7 +5,6 @@ use crate::mir::*; use crate::ty::subst::Subst; -use crate::ty::util::IntTypeExt; use crate::ty::{self, Ty, TyCtxt}; use rustc_hir as hir; use rustc_target::abi::VariantIdx; @@ -174,17 +173,7 @@ impl<'tcx> Rvalue<'tcx> { tcx.intern_tup(&[ty, tcx.types.bool]) } Rvalue::UnaryOp(UnOp::Not | UnOp::Neg, ref operand) => operand.ty(local_decls, tcx), - Rvalue::Discriminant(ref place) => { - let ty = place.ty(local_decls, tcx).ty; - match ty.kind { - ty::Adt(adt_def, _) => adt_def.repr.discr_type().to_ty(tcx), - ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx), - _ => { - // This can only be `0`, for now, so `u8` will suffice. - tcx.types.u8 - } - } - } + Rvalue::Discriminant(ref place) => place.ty(local_decls, tcx).ty.discriminant_ty(tcx), Rvalue::NullaryOp(NullOp::Box, t) => tcx.mk_box(t), Rvalue::NullaryOp(NullOp::SizeOf, _) => tcx.types.usize, Rvalue::Aggregate(ref ak, ref ops) => match **ak { diff --git a/src/librustc_middle/ty/mod.rs b/src/librustc_middle/ty/mod.rs index 01517ab25a24a..4cd3be932def0 100644 --- a/src/librustc_middle/ty/mod.rs +++ b/src/librustc_middle/ty/mod.rs @@ -2037,6 +2037,8 @@ impl ReprOptions { self.flags.contains(ReprFlags::HIDE_NICHE) } + /// Returns the discriminant type, given these `repr` options. + /// This must only be called on enums! pub fn discr_type(&self) -> attr::IntType { self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize)) } @@ -2269,6 +2271,7 @@ impl<'tcx> AdtDef { #[inline] pub fn eval_explicit_discr(&self, tcx: TyCtxt<'tcx>, expr_did: DefId) -> Option> { + assert!(self.is_enum()); let param_env = tcx.param_env(expr_did); let repr_type = self.repr.discr_type(); match tcx.const_eval_poly(expr_did) { @@ -2305,6 +2308,7 @@ impl<'tcx> AdtDef { &'tcx self, tcx: TyCtxt<'tcx>, ) -> impl Iterator)> + Captures<'tcx> { + assert!(self.is_enum()); let repr_type = self.repr.discr_type(); let initial = repr_type.initial_discriminant(tcx); let mut prev_discr = None::>; @@ -2337,6 +2341,7 @@ impl<'tcx> AdtDef { tcx: TyCtxt<'tcx>, variant_index: VariantIdx, ) -> Discr<'tcx> { + assert!(self.is_enum()); let (val, offset) = self.discriminant_def_for_variant(variant_index); let explicit_value = val .and_then(|expr_did| self.eval_explicit_discr(tcx, expr_did)) diff --git a/src/librustc_middle/ty/sty.rs b/src/librustc_middle/ty/sty.rs index ef77d1b5b3f81..f4962ced6c03a 100644 --- a/src/librustc_middle/ty/sty.rs +++ b/src/librustc_middle/ty/sty.rs @@ -29,6 +29,7 @@ use std::borrow::Cow; use std::cmp::Ordering; use std::marker::PhantomData; use std::ops::Range; +use ty::util::IntTypeExt; #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)] #[derive(HashStable, TypeFoldable, Lift)] @@ -2096,7 +2097,9 @@ impl<'tcx> TyS<'tcx> { variant_index: VariantIdx, ) -> Option> { match self.kind { - TyKind::Adt(adt, _) => Some(adt.discriminant_for_variant(tcx, variant_index)), + TyKind::Adt(adt, _) if adt.is_enum() => { + Some(adt.discriminant_for_variant(tcx, variant_index)) + } TyKind::Generator(def_id, substs, _) => { Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index)) } @@ -2104,6 +2107,18 @@ impl<'tcx> TyS<'tcx> { } } + /// Returns the type of the discriminant of this type. + pub fn discriminant_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { + match self.kind { + ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx), + ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx), + _ => { + // This can only be `0`, for now, so `u8` will suffice. + tcx.types.u8 + } + } + } + /// When we create a closure, we record its kind (i.e., what trait /// it implements) into its `ClosureSubsts` using a type /// parameter. This is kind of a phantom type, except that the diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs index 55f254f573261..115a472cabe5e 100644 --- a/src/librustc_mir/interpret/intrinsics.rs +++ b/src/librustc_mir/interpret/intrinsics.rs @@ -220,15 +220,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { sym::discriminant_value => { let place = self.deref_operand(args[0])?; let discr_val = self.read_discriminant(place.into())?.0; - let scalar = match dest.layout.ty.kind { - ty::Int(_) => Scalar::from_int( - self.sign_extend(discr_val, dest.layout) as i128, - dest.layout.size, - ), - ty::Uint(_) => Scalar::from_uint(discr_val, dest.layout.size), - _ => bug!("invalid `discriminant_value` return layout: {:?}", dest.layout), - }; - self.write_scalar(scalar, dest)?; + self.write_scalar(discr_val, dest)?; } sym::unchecked_shl | sym::unchecked_shr diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs index 95bc9810dab80..e359c7795c013 100644 --- a/src/librustc_mir/interpret/operand.rs +++ b/src/librustc_mir/interpret/operand.rs @@ -7,16 +7,16 @@ use std::fmt::Write; use rustc_errors::ErrorReported; use rustc_hir::def::Namespace; use rustc_macros::HashStable; -use rustc_middle::ty::layout::{IntegerExt, PrimitiveExt, TyAndLayout}; +use rustc_middle::ty::layout::{PrimitiveExt, TyAndLayout}; use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter, Printer}; use rustc_middle::ty::Ty; use rustc_middle::{mir, ty}; -use rustc_target::abi::{Abi, DiscriminantKind, HasDataLayout, Integer, LayoutOf, Size}; +use rustc_target::abi::{Abi, DiscriminantKind, HasDataLayout, LayoutOf, Size}; use rustc_target::abi::{VariantIdx, Variants}; use super::{ - from_known_layout, sign_extend, truncate, ConstValue, GlobalId, InterpCx, InterpResult, - MPlaceTy, Machine, MemPlace, Place, PlaceTy, Pointer, Scalar, ScalarMaybeUninit, + from_known_layout, ConstValue, GlobalId, InterpCx, InterpResult, MPlaceTy, Machine, MemPlace, + Place, PlaceTy, Pointer, Scalar, ScalarMaybeUninit, }; /// An `Immediate` represents a single immediate self-contained Rust value. @@ -469,6 +469,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { .try_fold(base_op, |op, elem| self.operand_projection(op, elem))?; trace!("eval_place_to_op: got {:?}", *op); + // Sanity-check the type we ended up with. + debug_assert_eq!( + self.subst_from_current_frame_and_normalize_erasing_regions( + place.ty(&self.frame().body.local_decls, *self.tcx).ty + ), + op.layout.ty, + ); Ok(op) } @@ -576,98 +583,113 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { /// Read discriminant, return the runtime value as well as the variant index. pub fn read_discriminant( &self, - rval: OpTy<'tcx, M::PointerTag>, - ) -> InterpResult<'tcx, (u128, VariantIdx)> { - trace!("read_discriminant_value {:#?}", rval.layout); - - let (discr_layout, discr_kind, discr_index) = match rval.layout.variants { + op: OpTy<'tcx, M::PointerTag>, + ) -> InterpResult<'tcx, (Scalar, VariantIdx)> { + trace!("read_discriminant_value {:#?}", op.layout); + + // Get type and layout of the discriminant. + let discr_layout = self.layout_of(op.layout.ty.discriminant_ty(*self.tcx))?; + trace!("discriminant type: {:?}", discr_layout.ty); + + // We use "discriminant" to refer to the value associated with a particular enum variant. + // This is not to be confused with its "variant index", which is just determining its position in the + // declared list of variants -- they can differ with explicitly assigned discriminants. + // We use "tag" to refer to how the discriminant is encoded in memory, which can be either + // straight-forward (`DiscriminantKind::Tag`) or with a niche (`DiscriminantKind::Niche`). + // Unfortunately, the rest of the compiler calls the latter "discriminant", too, which makes things + // rather confusing. + let (tag_scalar_layout, tag_kind, tag_index) = match op.layout.variants { Variants::Single { index } => { - let discr_val = rval - .layout - .ty - .discriminant_for_variant(*self.tcx, index) - .map_or(u128::from(index.as_u32()), |discr| discr.val); - return Ok((discr_val, index)); + let discr = match op.layout.ty.discriminant_for_variant(*self.tcx, index) { + Some(discr) => { + // This type actually has discriminants. + assert_eq!(discr.ty, discr_layout.ty); + Scalar::from_uint(discr.val, discr_layout.size) + } + None => { + // On a type without actual discriminants, variant is 0. + assert_eq!(index.as_u32(), 0); + Scalar::from_uint(index.as_u32(), discr_layout.size) + } + }; + return Ok((discr, index)); } - Variants::Multiple { discr: ref discr_layout, ref discr_kind, discr_index, .. } => { - (discr_layout, discr_kind, discr_index) + Variants::Multiple { ref discr, ref discr_kind, discr_index, .. } => { + (discr, discr_kind, discr_index) } }; - // read raw discriminant value - let discr_op = self.operand_field(rval, discr_index)?; - let discr_val = self.read_immediate(discr_op)?; - let raw_discr = discr_val.to_scalar_or_undef(); - trace!("discr value: {:?}", raw_discr); - // post-process - Ok(match *discr_kind { + // There are *three* layouts that come into play here: + // - The discriminant has a type for typechecking. This is `discr_layout`, and is used for + // the `Scalar` we return. + // - The tag (encoded discriminant) has layout `tag_layout`. This is always an integer type, + // and used to interpret the value we read from the tag field. + // For the return value, a cast to `discr_layout` is performed. + // - The field storing the tag has a layout, which is very similar to `tag_layout` but + // may be a pointer. This is `tag_val.layout`; we just use it for sanity checks. + + // Get layout for tag. + let tag_layout = self.layout_of(tag_scalar_layout.value.to_int_ty(*self.tcx))?; + + // Read tag and sanity-check `tag_layout`. + let tag_val = self.read_immediate(self.operand_field(op, tag_index)?)?; + assert_eq!(tag_layout.size, tag_val.layout.size); + assert_eq!(tag_layout.abi.is_signed(), tag_val.layout.abi.is_signed()); + let tag_val = tag_val.to_scalar()?; + trace!("tag value: {:?}", tag_val); + + // Figure out which discriminant and variant this corresponds to. + Ok(match *tag_kind { DiscriminantKind::Tag => { - let bits_discr = raw_discr - .not_undef() - .and_then(|raw_discr| self.force_bits(raw_discr, discr_val.layout.size)) - .map_err(|_| err_ub!(InvalidDiscriminant(raw_discr.erase_tag())))?; - let real_discr = if discr_val.layout.abi.is_signed() { - // going from layout tag type to typeck discriminant type - // requires first sign extending with the discriminant layout - let sexted = sign_extend(bits_discr, discr_val.layout.size); - // and then zeroing with the typeck discriminant type - let discr_ty = rval - .layout - .ty - .ty_adt_def() - .expect("tagged layout corresponds to adt") - .repr - .discr_type(); - let size = Integer::from_attr(self, discr_ty).size(); - truncate(sexted, size) - } else { - bits_discr - }; - // Make sure we catch invalid discriminants - let index = match rval.layout.ty.kind { + let tag_bits = self + .force_bits(tag_val, tag_layout.size) + .map_err(|_| err_ub!(InvalidDiscriminant(tag_val.erase_tag())))?; + // Cast bits from tag layout to discriminant layout. + let discr_val_cast = self.cast_from_scalar(tag_bits, tag_layout, discr_layout.ty); + let discr_bits = discr_val_cast.assert_bits(discr_layout.size); + // Convert discriminant to variant index, and catch invalid discriminants. + let index = match op.layout.ty.kind { ty::Adt(adt, _) => { - adt.discriminants(self.tcx.tcx).find(|(_, var)| var.val == real_discr) + adt.discriminants(self.tcx.tcx).find(|(_, var)| var.val == discr_bits) } ty::Generator(def_id, substs, _) => { let substs = substs.as_generator(); substs .discriminants(def_id, self.tcx.tcx) - .find(|(_, var)| var.val == real_discr) + .find(|(_, var)| var.val == discr_bits) } _ => bug!("tagged layout for non-adt non-generator"), } - .ok_or_else(|| err_ub!(InvalidDiscriminant(raw_discr.erase_tag())))?; - (real_discr, index.0) + .ok_or_else(|| err_ub!(InvalidDiscriminant(tag_val.erase_tag())))?; + // Return the cast value, and the index. + (discr_val_cast, index.0) } DiscriminantKind::Niche { dataful_variant, ref niche_variants, niche_start } => { + // Compute the variant this niche value/"tag" corresponds to. With niche layout, + // discriminant (encoded in niche/tag) and variant index are the same. let variants_start = niche_variants.start().as_u32(); let variants_end = niche_variants.end().as_u32(); - let raw_discr = raw_discr - .not_undef() - .map_err(|_| err_ub!(InvalidDiscriminant(ScalarMaybeUninit::Uninit)))?; - match raw_discr.to_bits_or_ptr(discr_val.layout.size, self) { + let variant = match tag_val.to_bits_or_ptr(tag_layout.size, self) { Err(ptr) => { // The niche must be just 0 (which an inbounds pointer value never is) let ptr_valid = niche_start == 0 && variants_start == variants_end && !self.memory.ptr_may_be_null(ptr); if !ptr_valid { - throw_ub!(InvalidDiscriminant(raw_discr.erase_tag().into())) + throw_ub!(InvalidDiscriminant(tag_val.erase_tag())) } - (u128::from(dataful_variant.as_u32()), dataful_variant) + dataful_variant } - Ok(raw_discr) => { + Ok(tag_bits) => { // We need to use machine arithmetic to get the relative variant idx: - // variant_index_relative = discr_val - niche_start_val - let discr_layout = - self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?; - let discr_val = ImmTy::from_uint(raw_discr, discr_layout); - let niche_start_val = ImmTy::from_uint(niche_start, discr_layout); + // variant_index_relative = tag_val - niche_start_val + let tag_val = ImmTy::from_uint(tag_bits, tag_layout); + let niche_start_val = ImmTy::from_uint(niche_start, tag_layout); let variant_index_relative_val = - self.binary_op(mir::BinOp::Sub, discr_val, niche_start_val)?; + self.binary_op(mir::BinOp::Sub, tag_val, niche_start_val)?; let variant_index_relative = variant_index_relative_val .to_scalar()? - .assert_bits(discr_val.layout.size); + .assert_bits(tag_val.layout.size); // Check if this is in the range that indicates an actual discriminant. if variant_index_relative <= u128::from(variants_end - variants_start) { let variant_index_relative = u32::try_from(variant_index_relative) @@ -676,7 +698,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { let variant_index = variants_start .checked_add(variant_index_relative) .expect("overflow computing absolute variant idx"); - let variants_len = rval + let variants_len = op .layout .ty .ty_adt_def() @@ -684,12 +706,16 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { .variants .len(); assert!(usize::try_from(variant_index).unwrap() < variants_len); - (u128::from(variant_index), VariantIdx::from_u32(variant_index)) + VariantIdx::from_u32(variant_index) } else { - (u128::from(dataful_variant.as_u32()), dataful_variant) + dataful_variant } } - } + }; + // Compute the size of the scalar we need to return. + // No need to cast, because the variant index directly serves as discriminant and is + // encoded in the tag. + (Scalar::from_uint(variant.as_u32(), discr_layout.size), variant) } }) } diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs index dc6967c2c49e5..36765ea7a8c46 100644 --- a/src/librustc_mir/interpret/place.rs +++ b/src/librustc_mir/interpret/place.rs @@ -638,6 +638,13 @@ where } self.dump_place(place_ty.place); + // Sanity-check the type we ended up with. + debug_assert_eq!( + self.subst_from_current_frame_and_normalize_erasing_regions( + place.ty(&self.frame().body.local_decls, *self.tcx).ty + ), + place_ty.layout.ty, + ); Ok(place_ty) } diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs index fd9815975c19f..bd4df788057e2 100644 --- a/src/librustc_mir/interpret/step.rs +++ b/src/librustc_mir/interpret/step.rs @@ -262,8 +262,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { Discriminant(place) => { let op = self.eval_place_to_op(place, None)?; let discr_val = self.read_discriminant(op)?.0; - let size = dest.layout.size; - self.write_scalar(Scalar::from_uint(discr_val, size), dest)?; + self.write_scalar(discr_val, dest)?; } }