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Auto merge of rust-lang#122629 - RalfJung:assert-unsafe-precondition,…
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… r=saethlin

refactor check_{lang,library}_ub: use a single intrinsic

This enacts the plan I laid out [here](rust-lang#122282 (comment)): use a single intrinsic, called `ub_checks` (in aniticpation of rust-lang/compiler-team#725), that just exposes the value of `debug_assertions` (consistently implemented in both codegen and the interpreter). Put the language vs library UB logic into the library.

This makes it easier to do something like rust-lang#122282 in the future: that just slightly alters the semantics of `ub_checks` (making it more approximating when crates built with different flags are mixed), but it no longer affects whether these checks can happen in Miri or compile-time.

The first commit just moves things around; I don't think these macros and functions belong into `intrinsics.rs` as they are not intrinsics.

r? `@saethlin`
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bors authored and RenjiSann committed Mar 25, 2024
2 parents 343bf41 + 3664b6a commit a23defa
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Showing 48 changed files with 314 additions and 292 deletions.
2 changes: 1 addition & 1 deletion compiler/rustc_borrowck/src/type_check/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2000,7 +2000,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
ConstraintCategory::SizedBound,
);
}
&Rvalue::NullaryOp(NullOp::UbCheck(_), _) => {}
&Rvalue::NullaryOp(NullOp::UbChecks, _) => {}

Rvalue::ShallowInitBox(operand, ty) => {
self.check_operand(operand, location);
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2 changes: 1 addition & 1 deletion compiler/rustc_codegen_cranelift/src/base.rs
Original file line number Diff line number Diff line change
Expand Up @@ -780,7 +780,7 @@ fn codegen_stmt<'tcx>(
NullOp::OffsetOf(fields) => {
layout.offset_of_subfield(fx, fields.iter()).bytes()
}
NullOp::UbCheck(_) => {
NullOp::UbChecks => {
let val = fx.tcx.sess.opts.debug_assertions;
let val = CValue::by_val(
fx.bcx.ins().iconst(types::I8, i64::try_from(val).unwrap()),
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3 changes: 1 addition & 2 deletions compiler/rustc_codegen_ssa/src/mir/rvalue.rs
Original file line number Diff line number Diff line change
Expand Up @@ -680,8 +680,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
let val = layout.offset_of_subfield(bx.cx(), fields.iter()).bytes();
bx.cx().const_usize(val)
}
mir::NullOp::UbCheck(_) => {
// In codegen, we want to check for language UB and library UB
mir::NullOp::UbChecks => {
let val = bx.tcx().sess.opts.debug_assertions;
bx.cx().const_bool(val)
}
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12 changes: 1 addition & 11 deletions compiler/rustc_const_eval/src/interpret/step.rs
Original file line number Diff line number Diff line change
Expand Up @@ -258,17 +258,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let val = layout.offset_of_subfield(self, fields.iter()).bytes();
Scalar::from_target_usize(val, self)
}
mir::NullOp::UbCheck(kind) => {
// We want to enable checks for library UB, because the interpreter doesn't
// know about those on its own.
// But we want to disable checks for language UB, because the interpreter
// has its own better checks for that.
let should_check = match kind {
mir::UbKind::LibraryUb => self.tcx.sess.opts.debug_assertions,
mir::UbKind::LanguageUb => false,
};
Scalar::from_bool(should_check)
}
mir::NullOp::UbChecks => Scalar::from_bool(self.tcx.sess.opts.debug_assertions),
};
self.write_scalar(val, &dest)?;
}
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Original file line number Diff line number Diff line change
Expand Up @@ -558,7 +558,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
Rvalue::Cast(_, _, _) => {}

Rvalue::NullaryOp(
NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(_) | NullOp::UbCheck(_),
NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(_) | NullOp::UbChecks,
_,
) => {}
Rvalue::ShallowInitBox(_, _) => {}
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2 changes: 1 addition & 1 deletion compiler/rustc_const_eval/src/transform/validate.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1167,7 +1167,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
Rvalue::Repeat(_, _)
| Rvalue::ThreadLocalRef(_)
| Rvalue::AddressOf(_, _)
| Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf | NullOp::UbCheck(_), _)
| Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf | NullOp::UbChecks, _)
| Rvalue::Discriminant(_) => {}
}
self.super_rvalue(rvalue, location);
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5 changes: 2 additions & 3 deletions compiler/rustc_hir_analysis/src/check/intrinsic.rs
Original file line number Diff line number Diff line change
Expand Up @@ -127,8 +127,7 @@ pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -
| sym::variant_count
| sym::is_val_statically_known
| sym::ptr_mask
| sym::check_language_ub
| sym::check_library_ub
| sym::ub_checks
| sym::fadd_algebraic
| sym::fsub_algebraic
| sym::fmul_algebraic
Expand Down Expand Up @@ -571,7 +570,7 @@ pub fn check_intrinsic_type(
(0, 0, vec![Ty::new_imm_ptr(tcx, Ty::new_unit(tcx))], tcx.types.usize)
}

sym::check_language_ub | sym::check_library_ub => (0, 1, Vec::new(), tcx.types.bool),
sym::ub_checks => (0, 1, Vec::new(), tcx.types.bool),

sym::simd_eq
| sym::simd_ne
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2 changes: 1 addition & 1 deletion compiler/rustc_middle/src/mir/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -796,7 +796,7 @@ impl<'tcx> Body<'tcx> {
}

match rvalue {
Rvalue::NullaryOp(NullOp::UbCheck(_), _) => {
Rvalue::NullaryOp(NullOp::UbChecks, _) => {
Some((tcx.sess.opts.debug_assertions as u128, targets))
}
Rvalue::Use(Operand::Constant(constant)) => {
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2 changes: 1 addition & 1 deletion compiler/rustc_middle/src/mir/pretty.rs
Original file line number Diff line number Diff line change
Expand Up @@ -944,7 +944,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
NullOp::SizeOf => write!(fmt, "SizeOf({t})"),
NullOp::AlignOf => write!(fmt, "AlignOf({t})"),
NullOp::OffsetOf(fields) => write!(fmt, "OffsetOf({t}, {fields:?})"),
NullOp::UbCheck(kind) => write!(fmt, "UbCheck({kind:?})"),
NullOp::UbChecks => write!(fmt, "UbChecks()"),
}
}
ThreadLocalRef(did) => ty::tls::with(|tcx| {
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13 changes: 3 additions & 10 deletions compiler/rustc_middle/src/mir/syntax.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1361,16 +1361,9 @@ pub enum NullOp<'tcx> {
AlignOf,
/// Returns the offset of a field
OffsetOf(&'tcx List<(VariantIdx, FieldIdx)>),
/// Returns whether we want to check for library UB or language UB at monomorphization time.
/// Both kinds of UB evaluate to `true` in codegen, and only library UB evalutes to `true` in
/// const-eval/Miri, because the interpreter has its own better checks for language UB.
UbCheck(UbKind),
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
pub enum UbKind {
LanguageUb,
LibraryUb,
/// Returns whether we want to check for UB.
/// This returns the value of `cfg!(debug_assertions)` at monomorphization time.
UbChecks,
}

#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
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2 changes: 1 addition & 1 deletion compiler/rustc_middle/src/mir/tcx.rs
Original file line number Diff line number Diff line change
Expand Up @@ -194,7 +194,7 @@ impl<'tcx> Rvalue<'tcx> {
Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(..), _) => {
tcx.types.usize
}
Rvalue::NullaryOp(NullOp::UbCheck(_), _) => tcx.types.bool,
Rvalue::NullaryOp(NullOp::UbChecks, _) => tcx.types.bool,
Rvalue::Aggregate(ref ak, ref ops) => match **ak {
AggregateKind::Array(ty) => Ty::new_array(tcx, ty, ops.len() as u64),
AggregateKind::Tuple => {
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_mir_dataflow/src/move_paths/builder.rs
Original file line number Diff line number Diff line change
Expand Up @@ -433,7 +433,7 @@ impl<'b, 'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> Gatherer<'b, 'a, 'tcx, F> {
| Rvalue::Discriminant(..)
| Rvalue::Len(..)
| Rvalue::NullaryOp(
NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(..) | NullOp::UbCheck(_),
NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(..) | NullOp::UbChecks,
_,
) => {}
}
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2 changes: 1 addition & 1 deletion compiler/rustc_mir_transform/src/gvn.rs
Original file line number Diff line number Diff line change
Expand Up @@ -487,7 +487,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
NullOp::OffsetOf(fields) => {
layout.offset_of_subfield(&self.ecx, fields.iter()).bytes()
}
NullOp::UbCheck(_) => return None,
NullOp::UbChecks => return None,
};
let usize_layout = self.ecx.layout_of(self.tcx.types.usize).unwrap();
let imm = ImmTy::try_from_uint(val, usize_layout)?;
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2 changes: 1 addition & 1 deletion compiler/rustc_mir_transform/src/known_panics_lint.rs
Original file line number Diff line number Diff line change
Expand Up @@ -639,7 +639,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
NullOp::OffsetOf(fields) => {
op_layout.offset_of_subfield(self, fields.iter()).bytes()
}
NullOp::UbCheck(_) => return None,
NullOp::UbChecks => return None,
};
ImmTy::from_scalar(Scalar::from_target_usize(val, self), layout).into()
}
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21 changes: 2 additions & 19 deletions compiler/rustc_mir_transform/src/lower_intrinsics.rs
Original file line number Diff line number Diff line change
Expand Up @@ -20,30 +20,13 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
sym::unreachable => {
terminator.kind = TerminatorKind::Unreachable;
}
sym::check_language_ub => {
sym::ub_checks => {
let target = target.unwrap();
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::NullaryOp(
NullOp::UbCheck(UbKind::LanguageUb),
tcx.types.bool,
),
))),
});
terminator.kind = TerminatorKind::Goto { target };
}
sym::check_library_ub => {
let target = target.unwrap();
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::NullaryOp(
NullOp::UbCheck(UbKind::LibraryUb),
tcx.types.bool,
),
Rvalue::NullaryOp(NullOp::UbChecks, tcx.types.bool),
))),
});
terminator.kind = TerminatorKind::Goto { target };
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_mir_transform/src/promote_consts.rs
Original file line number Diff line number Diff line change
Expand Up @@ -446,7 +446,7 @@ impl<'tcx> Validator<'_, 'tcx> {
NullOp::SizeOf => {}
NullOp::AlignOf => {}
NullOp::OffsetOf(_) => {}
NullOp::UbCheck(_) => {}
NullOp::UbChecks => {}
},

Rvalue::ShallowInitBox(_, _) => return Err(Unpromotable),
Expand Down
8 changes: 1 addition & 7 deletions compiler/rustc_smir/src/rustc_smir/convert/mir.rs
Original file line number Diff line number Diff line change
Expand Up @@ -251,19 +251,13 @@ impl<'tcx> Stable<'tcx> for mir::NullOp<'tcx> {
type T = stable_mir::mir::NullOp;
fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
use rustc_middle::mir::NullOp::*;
use rustc_middle::mir::UbKind;
match self {
SizeOf => stable_mir::mir::NullOp::SizeOf,
AlignOf => stable_mir::mir::NullOp::AlignOf,
OffsetOf(indices) => stable_mir::mir::NullOp::OffsetOf(
indices.iter().map(|idx| idx.stable(tables)).collect(),
),
UbCheck(UbKind::LanguageUb) => {
stable_mir::mir::NullOp::UbCheck(stable_mir::mir::UbKind::LanguageUb)
}
UbCheck(UbKind::LibraryUb) => {
stable_mir::mir::NullOp::UbCheck(stable_mir::mir::UbKind::LibraryUb)
}
UbChecks => stable_mir::mir::NullOp::UbChecks,
}
}
}
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3 changes: 1 addition & 2 deletions compiler/rustc_span/src/symbol.rs
Original file line number Diff line number Diff line change
Expand Up @@ -518,8 +518,6 @@ symbols! {
cfi,
cfi_encoding,
char,
check_language_ub,
check_library_ub,
client,
clippy,
clobber_abi,
Expand Down Expand Up @@ -1867,6 +1865,7 @@ symbols! {
u8_legacy_fn_max_value,
u8_legacy_fn_min_value,
u8_legacy_mod,
ub_checks,
unaligned_volatile_load,
unaligned_volatile_store,
unboxed_closures,
Expand Down
10 changes: 2 additions & 8 deletions compiler/stable_mir/src/mir/body.rs
Original file line number Diff line number Diff line change
Expand Up @@ -621,7 +621,7 @@ impl Rvalue {
Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(..), _) => {
Ok(Ty::usize_ty())
}
Rvalue::NullaryOp(NullOp::UbCheck(_), _) => Ok(Ty::bool_ty()),
Rvalue::NullaryOp(NullOp::UbChecks, _) => Ok(Ty::bool_ty()),
Rvalue::Aggregate(ak, ops) => match *ak {
AggregateKind::Array(ty) => Ty::try_new_array(ty, ops.len() as u64),
AggregateKind::Tuple => Ok(Ty::new_tuple(
Expand Down Expand Up @@ -989,13 +989,7 @@ pub enum NullOp {
/// Returns the offset of a field.
OffsetOf(Vec<(VariantIdx, FieldIdx)>),
/// cfg!(debug_assertions), but at codegen time
UbCheck(UbKind),
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum UbKind {
LanguageUb,
LibraryUb,
UbChecks,
}

impl Operand {
Expand Down
2 changes: 1 addition & 1 deletion library/core/src/char/convert.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,9 @@ use crate::char::TryFromCharError;
use crate::convert::TryFrom;
use crate::error::Error;
use crate::fmt;
use crate::intrinsics::assert_unsafe_precondition;
use crate::mem::transmute;
use crate::str::FromStr;
use crate::ub_checks::assert_unsafe_precondition;

/// Converts a `u32` to a `char`. See [`char::from_u32`].
#[must_use]
Expand Down
5 changes: 3 additions & 2 deletions library/core/src/hint.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
//! Hints may be compile time or runtime.
use crate::intrinsics;
use crate::ub_checks;

/// Informs the compiler that the site which is calling this function is not
/// reachable, possibly enabling further optimizations.
Expand Down Expand Up @@ -98,7 +99,7 @@ use crate::intrinsics;
#[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn unreachable_unchecked() -> ! {
intrinsics::assert_unsafe_precondition!(
ub_checks::assert_unsafe_precondition!(
check_language_ub,
"hint::unreachable_unchecked must never be reached",
() => false
Expand Down Expand Up @@ -148,7 +149,7 @@ pub const unsafe fn unreachable_unchecked() -> ! {
pub const unsafe fn assert_unchecked(cond: bool) {
// SAFETY: The caller promised `cond` is true.
unsafe {
intrinsics::assert_unsafe_precondition!(
ub_checks::assert_unsafe_precondition!(
check_language_ub,
"hint::assert_unchecked must never be called when the condition is false",
(cond: bool = cond) => cond,
Expand Down
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