Skip to content

Commit

Permalink
Add range information to slice metadata for types that are known to n…
Browse files Browse the repository at this point in the history 
…ot be ZST
  • Loading branch information
@the8472
the8472 committed Mar 24, 2024
1 parent 020bbe4 commit e47adf2
Show file tree
Hide file tree
Showing 15 changed files with 296 additions and 52 deletions.
14 changes: 13 additions & 1 deletion compiler/rustc_hir/src/hir.rs
View file
Expand Up @@ -3771,14 +3771,26 @@ impl<'hir> Node<'hir> {
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
mod size_asserts {
use super::*;
// tidy-alphabetical-start
static_assert_size!(Block<'_>, 48);
static_assert_size!(Body<'_>, 24);
#[cfg(bootstrap)]
static_assert_size!(Expr<'_>, 64);
#[cfg(not(bootstrap))]
static_assert_size!(Expr<'_>, 56);
#[cfg(bootstrap)]
static_assert_size!(ExprKind<'_>, 48);
#[cfg(not(bootstrap))]
static_assert_size!(ExprKind<'_>, 40);
static_assert_size!(FnDecl<'_>, 40);
#[cfg(bootstrap)]
static_assert_size!(ForeignItem<'_>, 72);
#[cfg(not(bootstrap))]
static_assert_size!(ForeignItem<'_>, 64);
#[cfg(bootstrap)]
static_assert_size!(ForeignItemKind<'_>, 40);
#[cfg(not(bootstrap))]
static_assert_size!(ForeignItemKind<'_>, 32);
// tidy-alphabetical-start
static_assert_size!(GenericArg<'_>, 32);
static_assert_size!(GenericBound<'_>, 48);
static_assert_size!(Generics<'_>, 56);
Expand Down
27 changes: 16 additions & 11 deletions compiler/rustc_hir_typeck/src/intrinsicck.rs
View file
Expand Up @@ -4,7 +4,7 @@ use rustc_hir as hir;
use rustc_index::Idx;
use rustc_middle::ty::layout::{LayoutError, SizeSkeleton};
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
use rustc_target::abi::{Pointer, VariantIdx};
use rustc_target::abi::{Pointer, Size, VariantIdx};

use super::FnCtxt;

Expand Down Expand Up @@ -84,19 +84,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
}

fn size_to_bits(size: Size) -> u128 {
let Some(bits) = u128::from(size.bytes()).checked_mul(8) else {
// `u128` should definitely be able to hold the size of different architectures
// larger sizes should be reported as error `are too big for the current architecture`
// otherwise we have a bug somewhere
bug!("{:?} overflow for u128", size)
};

bits
}

// Try to display a sensible error with as much information as possible.
let skeleton_string = |ty: Ty<'tcx>, sk: Result<_, &_>| match sk {
Ok(SizeSkeleton::Pointer { tail, .. }) => format!("pointer to `{tail}`"),
Ok(SizeSkeleton::Known(size)) => {
if let Some(v) = u128::from(size.bytes()).checked_mul(8) {
format!("{v} bits")
} else {
// `u128` should definitely be able to hold the size of different architectures
// larger sizes should be reported as error `are too big for the current architecture`
// otherwise we have a bug somewhere
bug!("{:?} overflow for u128", size)
}
Ok(SizeSkeleton::Pointer { tail, known_size: Some(size), .. }) => {
format!("{} bits, pointer to `{tail}`", size_to_bits(size))
}
Ok(SizeSkeleton::Pointer { tail, .. }) => format!("pointer to `{tail}`"),
Ok(SizeSkeleton::Known(size)) => format!("{} bits", size_to_bits(size)),
Ok(SizeSkeleton::Generic(size)) => {
if let Some(size) = size.try_eval_target_usize(tcx, self.param_env) {
format!("{size} bytes")
Expand Down
35 changes: 29 additions & 6 deletions compiler/rustc_middle/src/ty/layout.rs
View file
Expand Up @@ -3,6 +3,7 @@ use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use crate::query::TyCtxtAt;
use crate::ty::normalize_erasing_regions::NormalizationError;
use crate::ty::{self, Ty, TyCtxt, TypeVisitableExt};
use hir::Mutability;
use rustc_error_messages::DiagMessage;
use rustc_errors::{
Diag, DiagArgValue, DiagCtxt, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
Expand Down Expand Up @@ -297,6 +298,8 @@ pub enum SizeSkeleton<'tcx> {
Pointer {
/// If true, this pointer is never null.
non_zero: bool,
/// Available if the width of the pointer is known, i.e. whether it's 1 or 2 usizes
known_size: Option<Size>,
/// The type which determines the unsized metadata, if any,
/// of this pointer. Either a type parameter or a projection
/// depending on one, with regions erased.
Expand Down Expand Up @@ -334,7 +337,23 @@ impl<'tcx> SizeSkeleton<'tcx> {
match tail.kind() {
ty::Param(_) | ty::Alias(ty::Projection | ty::Inherent, _) => {
debug_assert!(tail.has_non_region_param());
Ok(SizeSkeleton::Pointer { non_zero, tail: tcx.erase_regions(tail) })
Ok(SizeSkeleton::Pointer {
non_zero,
known_size: None,
tail: tcx.erase_regions(tail),
})
}
ty::Slice(_) => {
debug_assert!(tail.has_non_region_param());
// Assumption: all slice pointers have the same size. At most they differ in niches or or ptr/len ordering
let simple_slice =
Ty::new_ptr(tcx, Ty::new_slice(tcx, tcx.types.unit), Mutability::Not);
let size = tcx.layout_of(param_env.and(simple_slice)).unwrap().size;
Ok(SizeSkeleton::Pointer {
non_zero,
known_size: Some(size),
tail: tcx.erase_regions(tail),
})
}
_ => bug!(
"SizeSkeleton::compute({ty}): layout errored ({err:?}), yet \
Expand Down Expand Up @@ -407,7 +426,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
let v0 = zero_or_ptr_variant(0)?;
// Newtype.
if def.variants().len() == 1 {
if let Some(SizeSkeleton::Pointer { non_zero, tail }) = v0 {
if let Some(SizeSkeleton::Pointer { non_zero, known_size, tail }) = v0 {
return Ok(SizeSkeleton::Pointer {
non_zero: non_zero
|| match tcx.layout_scalar_valid_range(def.did()) {
Expand All @@ -417,6 +436,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
}
_ => false,
},
known_size,
tail,
});
} else {
Expand All @@ -427,9 +447,9 @@ impl<'tcx> SizeSkeleton<'tcx> {
let v1 = zero_or_ptr_variant(1)?;
// Nullable pointer enum optimization.
match (v0, v1) {
(Some(SizeSkeleton::Pointer { non_zero: true, tail }), None)
| (None, Some(SizeSkeleton::Pointer { non_zero: true, tail })) => {
Ok(SizeSkeleton::Pointer { non_zero: false, tail })
(Some(SizeSkeleton::Pointer { non_zero: true, known_size, tail }), None)
| (None, Some(SizeSkeleton::Pointer { non_zero: true, known_size, tail })) => {
Ok(SizeSkeleton::Pointer { non_zero: false, known_size, tail })
}
_ => Err(err),
}
Expand All @@ -450,7 +470,10 @@ impl<'tcx> SizeSkeleton<'tcx> {

pub fn same_size(self, other: SizeSkeleton<'tcx>) -> bool {
match (self, other) {
(SizeSkeleton::Known(a), SizeSkeleton::Known(b)) => a == b,
(
SizeSkeleton::Known(a) | SizeSkeleton::Pointer { known_size: Some(a), .. },
SizeSkeleton::Known(b) | SizeSkeleton::Pointer { known_size: Some(b), .. },
) => a == b,
(SizeSkeleton::Pointer { tail: a, .. }, SizeSkeleton::Pointer { tail: b, .. }) => {
a == b
}
Expand Down
195 changes: 191 additions & 4 deletions compiler/rustc_ty_utils/src/layout.rs
View file
@@ -1,3 +1,4 @@
use crate::layout::ty::ParamEnv;
use hir::def_id::DefId;
use rustc_hir as hir;
use rustc_index::bit_set::BitSet;
Expand All @@ -13,9 +14,12 @@ use rustc_session::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
use rustc_span::sym;
use rustc_span::symbol::Symbol;
use rustc_target::abi::*;
use rustc_type_ir::DynKind;

use std::cmp;
use std::fmt::Debug;
use std::iter;
use std::ops::ControlFlow;

use crate::errors::{
MultipleArrayFieldsSimdType, NonPrimitiveSimdType, OversizedSimdType, ZeroLengthSimdType,
Expand Down Expand Up @@ -123,7 +127,7 @@ fn layout_of_uncached<'tcx>(
};
debug_assert!(!ty.has_non_region_infer());

Ok(match *ty.kind() {
let layout = match *ty.kind() {
// Basic scalars.
ty::Bool => tcx.mk_layout(LayoutS::scalar(
cx,
Expand Down Expand Up @@ -201,10 +205,34 @@ fn layout_of_uncached<'tcx>(
return Ok(tcx.mk_layout(LayoutS::scalar(cx, data_ptr)));
}

let Abi::Scalar(metadata) = metadata_layout.abi else {
let Abi::Scalar(mut metadata) = metadata_layout.abi else {
return Err(error(cx, LayoutError::Unknown(pointee)));
};

// if !ty.is_unsafe_ptr() && metadata_ty == tcx.types.usize {
// let pointee_zst = is_trivially_non_zst(pointee, tcx);
// // eprintln!("usize-meta {:?} {}", pointee, pointee_zst);
// if pointee_zst {
// metadata.valid_range_mut().end = dl.ptr_sized_integer().signed_max() as u128;

if !ty.is_unsafe_ptr() {
match pointee.kind() {
ty::Slice(element) => match ty_is_non_zst(*element, param_env, tcx) {
NonZst::True => {
metadata.valid_range_mut().end =
dl.ptr_sized_integer().signed_max() as u128
}
NonZst::Unknown => return Err(error(cx, LayoutError::Unknown(ty))),
_ => {}
},
ty::Str => {
metadata.valid_range_mut().end =
dl.ptr_sized_integer().signed_max() as u128;
}
_ => {}
}
}

metadata
} else {
let unsized_part = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
Expand All @@ -213,7 +241,26 @@ fn layout_of_uncached<'tcx>(
ty::Foreign(..) => {
return Ok(tcx.mk_layout(LayoutS::scalar(cx, data_ptr)));
}
ty::Slice(_) | ty::Str => scalar_unit(Int(dl.ptr_sized_integer(), false)),
ty::Slice(element) => {
let mut metadata = scalar_unit(Int(dl.ptr_sized_integer(), false));
if !ty.is_unsafe_ptr() {
match ty_is_non_zst(*element, param_env, tcx) {
NonZst::True => {
metadata.valid_range_mut().end =
dl.ptr_sized_integer().signed_max() as u128
}
NonZst::Unknown => return Err(error(cx, LayoutError::Unknown(ty))),
_ => {}
}
}
metadata
}
ty::Str => {
let mut metadata = scalar_unit(Int(dl.ptr_sized_integer(), false));
metadata.valid_range_mut().end =
dl.ptr_sized_integer().signed_max() as u128;
metadata
}
ty::Dynamic(..) => {
let mut vtable = scalar_unit(Pointer(AddressSpace::DATA));
vtable.valid_range_mut().start = 1;
Expand Down Expand Up @@ -606,7 +653,147 @@ fn layout_of_uncached<'tcx>(
ty::Placeholder(..) | ty::Param(_) => {
return Err(error(cx, LayoutError::Unknown(ty)));
}
})
};

#[cfg(debug_assertions)]
if layout.is_sized() && !layout.abi.is_uninhabited() {
match (ty_is_non_zst(ty, param_env, tcx), layout.is_zst()) {
(NonZst::Unknown, _) => {
bug!("ZSTness should not be unknown at this point {:?} {:?}", ty, layout)
}
(NonZst::False | NonZst::Uninhabited, false) => {
bug!("{:?} is not a ZST but ty_is_non_zst() thinks it is", ty)
}
(NonZst::True, true) => bug!("{:?} is a ZST but ty_is_non_zst() thinks it isn't", ty),
_ => {}
}
}

Ok(layout)
}

fn ty_is_non_zst<'tcx>(ty: Ty<'tcx>, param_env: ParamEnv<'tcx>, tcx: TyCtxt<'tcx>) -> NonZst {
fn fold_fields<'tcx>(
mut it: impl Iterator<Item = Ty<'tcx>>,
param_env: ParamEnv<'tcx>,
tcx: TyCtxt<'tcx>,
) -> NonZst {
let (ControlFlow::Break(res) | ControlFlow::Continue(res)) =
it.try_fold(NonZst::False, |acc, ty| {
if acc == NonZst::True {
return ControlFlow::Break(acc);
}

ControlFlow::Continue(cmp::max(acc, ty_is_non_zst(ty, param_env, tcx)))
});

res
}

match ty.kind() {
ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
| ty::Uint(_)
| ty::Int(_)
| ty::Bool
| ty::Float(_)
| ty::FnPtr(_)
| ty::RawPtr(..)
| ty::Dynamic(_, _, DynKind::DynStar)
| ty::Char
| ty::Ref(..) => NonZst::True,

ty::Closure(_, args) => fold_fields(args.as_closure().upvar_tys().iter(), param_env, tcx),
ty::Coroutine(_, _) => NonZst::True,
ty::CoroutineClosure(_, args) => {
fold_fields(args.as_coroutine_closure().upvar_tys().iter(), param_env, tcx)
}
ty::Array(ty, len) => {
let len = if len.has_projections() {
tcx.normalize_erasing_regions(param_env, *len)
} else {
*len
};

if let Some(len) = len.try_to_target_usize(tcx) {
if len == 0 {
return NonZst::False;
}
let element_zst = ty_is_non_zst(*ty, param_env, tcx);
if element_zst != NonZst::Unknown {
return element_zst;
}
}
NonZst::Unknown
}
ty::Tuple(tys) => fold_fields(tys.iter(), param_env, tcx),
ty::Adt(def, args) => {
if ty.is_enum() {
if def.variants().len() == 0 {
return NonZst::Uninhabited;
}
// An enum is !ZST if
// * it has a repr and at least one non-uninhabited variant
// * it has at least one variant with a !ZST payload
// * it has multiple variants that are not uninhabited

let min_empty_variants = if def.repr().inhibit_enum_layout_opt() { 1 } else { 2 };

// first check without recursing
let simple_variants = def.variants().iter().filter(|v| v.fields.len() == 0).count();
if simple_variants >= min_empty_variants {
return NonZst::True;
}

let mut inhabited_zst_variants = 0;
let mut unknown = false;

for variant in def.variants().iter().filter(|v| v.fields.len() != 0) {
let variant_sized =
fold_fields(variant.fields.iter().map(|f| f.ty(tcx, args)), param_env, tcx);

match variant_sized {
// enum E { A(!, u32) } counts as !ZST for our purposes
NonZst::True => return NonZst::True,
NonZst::False => inhabited_zst_variants += 1,
NonZst::Unknown => unknown = true,
NonZst::Uninhabited => {}
}
}

if simple_variants + inhabited_zst_variants >= min_empty_variants {
return NonZst::True;
}
if unknown {
return NonZst::Unknown;
}
if simple_variants + inhabited_zst_variants == 0 {
return NonZst::Uninhabited;
}

NonZst::False
} else {
fold_fields(def.all_fields().map(|f| f.ty(tcx, args)), param_env, tcx)
}
}
ty::FnDef(..) => NonZst::False,
ty::Never => NonZst::Uninhabited,
ty::Param(..) => NonZst::Unknown,
// treat unsized types as potentially-ZST
ty::Dynamic(..) | ty::Slice(..) => NonZst::False,
ty::Alias(..) => match tcx.try_normalize_erasing_regions(param_env, ty) {
Ok(ty) if !matches!(ty.kind(), ty::Alias(..)) => ty_is_non_zst(ty, param_env, tcx),
_ => NonZst::Unknown,
},
_ => bug!("is_non_zst not implemented for this kind {:?}", ty),
}
}

#[derive(Clone, Copy, PartialEq, Eq, Debug, PartialOrd, Ord)]
pub enum NonZst {
False,
Uninhabited,
Unknown,
True,
}

/// Overlap eligibility and variant assignment for each CoroutineSavedLocal.
Expand Down

0 comments on commit e47adf2

Please sign in to comment.