Auto merge of #121271 - matthiaskrgr:rollup-56ru17w, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #118569 (Move `OsStr::slice_encoded_bytes` validation to platform modules)
 - #121067 (make "invalid fragment specifier" translatable)
 - #121224 (Remove unnecessary unit binding)
 - #121247 (Add help to `hir_analysis_unrecognized_intrinsic_function`)
 - #121257 (remove extraneous text from example config)
 - #121260 (Remove const_prop.rs)
 - #121266 (Add uncontroversial syscall doc aliases to std docs)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_expand/messages.ftl

@@ -61,6 +61,11 @@ expand_invalid_cfg_multiple_predicates = multiple `cfg` predicates are specified
 expand_invalid_cfg_no_parens = `cfg` is not followed by parentheses
 expand_invalid_cfg_no_predicate = `cfg` predicate is not specified
 expand_invalid_cfg_predicate_literal = `cfg` predicate key cannot be a literal
+
+expand_invalid_fragment_specifier =
+    invalid fragment specifier `{$fragment}`
+    .help = {$help}
+
 expand_macro_body_stability =
     macros cannot have body stability attributes
     .label = invalid body stability attribute

compiler/rustc_expand/src/errors.rs

@@ -408,3 +408,13 @@ pub struct DuplicateMatcherBinding {
     #[label(expand_label2)]
     pub prev: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(expand_invalid_fragment_specifier)]
+#[help]
+pub struct InvalidFragmentSpecifier {
+    #[primary_span]
+    pub span: Span,
+    pub fragment: Ident,
+    pub help: String,
+}

compiler/rustc_expand/src/mbe/quoted.rs

@@ -1,3 +1,4 @@
+use crate::errors;
 use crate::mbe::macro_parser::count_metavar_decls;
 use crate::mbe::{Delimited, KleeneOp, KleeneToken, MetaVarExpr, SequenceRepetition, TokenTree};
 
@@ -60,11 +61,11 @@ pub(super) fn parse(
                     Some(&tokenstream::TokenTree::Token(Token { kind: token::Colon, span }, _)) => {
                         match trees.next() {
                             Some(tokenstream::TokenTree::Token(token, _)) => match token.ident() {
-                                Some((frag, _)) => {
+                                Some((fragment, _)) => {
                                     let span = token.span.with_lo(start_sp.lo());
 
                                     let kind =
-                                        token::NonterminalKind::from_symbol(frag.name, || {
+                                        token::NonterminalKind::from_symbol(fragment.name, || {
                                             // FIXME(#85708) - once we properly decode a foreign
                                             // crate's `SyntaxContext::root`, then we can replace
                                             // this with just `span.edition()`. A
@@ -81,14 +82,13 @@ pub(super) fn parse(
                                         })
                                         .unwrap_or_else(
                                             || {
-                                                let msg = format!(
-                                                    "invalid fragment specifier `{}`",
-                                                    frag.name
+                                                sess.dcx().emit_err(
+                                                    errors::InvalidFragmentSpecifier {
+                                                        span,
+                                                        fragment,
+                                                        help: VALID_FRAGMENT_NAMES_MSG.into(),
+                                                    },
                                                 );
-                                                sess.dcx()
-                                                    .struct_span_err(span, msg)
-                                                    .with_help(VALID_FRAGMENT_NAMES_MSG)
-                                                    .emit();
                                                 token::NonterminalKind::Ident
                                             },
                                         );

compiler/rustc_hir_analysis/messages.ftl

@@ -469,6 +469,7 @@ hir_analysis_unrecognized_atomic_operation =
 hir_analysis_unrecognized_intrinsic_function =
     unrecognized intrinsic function: `{$name}`
     .label = unrecognized intrinsic
+    .help = if you're adding an intrinsic, be sure to update `check_intrinsic_type`
 
 hir_analysis_unused_associated_type_bounds =
     unnecessary associated type bound for not object safe associated type

compiler/rustc_hir_analysis/src/errors.rs

@@ -143,6 +143,7 @@ pub struct WrongNumberOfGenericArgumentsToIntrinsic<'a> {
 
 #[derive(Diagnostic)]
 #[diag(hir_analysis_unrecognized_intrinsic_function, code = E0093)]
+#[help]
 pub struct UnrecognizedIntrinsicFunction {
     #[primary_span]
     #[label]

compiler/rustc_mir_transform/src/const_prop.rs

@@ -9,17 +9,14 @@ use rustc_const_eval::interpret::{
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def::DefKind;
 use rustc_hir::HirId;
-use rustc_index::bit_set::BitSet;
-use rustc_index::{Idx, IndexVec};
-use rustc_middle::mir::visit::Visitor;
+use rustc_index::{bit_set::BitSet, Idx, IndexVec};
+use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::{self, ConstInt, ParamEnv, ScalarInt, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::Span;
 use rustc_target::abi::{Abi, FieldIdx, HasDataLayout, Size, TargetDataLayout, VariantIdx};
 
-use crate::const_prop::CanConstProp;
-use crate::const_prop::ConstPropMode;
 use crate::dataflow_const_prop::DummyMachine;
 use crate::errors::{AssertLint, AssertLintKind};
 use crate::MirLint;
@@ -849,3 +846,128 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
         }
     }
 }
+
+/// The maximum number of bytes that we'll allocate space for a local or the return value.
+/// Needed for #66397, because otherwise we eval into large places and that can cause OOM or just
+/// Severely regress performance.
+const MAX_ALLOC_LIMIT: u64 = 1024;
+
+/// The mode that `ConstProp` is allowed to run in for a given `Local`.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum ConstPropMode {
+    /// The `Local` can be propagated into and reads of this `Local` can also be propagated.
+    FullConstProp,
+    /// The `Local` can only be propagated into and from its own block.
+    OnlyInsideOwnBlock,
+    /// The `Local` cannot be part of propagation at all. Any statement
+    /// referencing it either for reading or writing will not get propagated.
+    NoPropagation,
+}
+
+pub struct CanConstProp {
+    can_const_prop: IndexVec<Local, ConstPropMode>,
+    // False at the beginning. Once set, no more assignments are allowed to that local.
+    found_assignment: BitSet<Local>,
+}
+
+impl CanConstProp {
+    /// Returns true if `local` can be propagated
+    pub fn check<'tcx>(
+        tcx: TyCtxt<'tcx>,
+        param_env: ParamEnv<'tcx>,
+        body: &Body<'tcx>,
+    ) -> IndexVec<Local, ConstPropMode> {
+        let mut cpv = CanConstProp {
+            can_const_prop: IndexVec::from_elem(ConstPropMode::FullConstProp, &body.local_decls),
+            found_assignment: BitSet::new_empty(body.local_decls.len()),
+        };
+        for (local, val) in cpv.can_const_prop.iter_enumerated_mut() {
+            let ty = body.local_decls[local].ty;
+            match tcx.layout_of(param_env.and(ty)) {
+                Ok(layout) if layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) => {}
+                // Either the layout fails to compute, then we can't use this local anyway
+                // or the local is too large, then we don't want to.
+                _ => {
+                    *val = ConstPropMode::NoPropagation;
+                    continue;
+                }
+            }
+        }
+        // Consider that arguments are assigned on entry.
+        for arg in body.args_iter() {
+            cpv.found_assignment.insert(arg);
+        }
+        cpv.visit_body(body);
+        cpv.can_const_prop
+    }
+}
+
+impl<'tcx> Visitor<'tcx> for CanConstProp {
+    fn visit_place(&mut self, place: &Place<'tcx>, mut context: PlaceContext, loc: Location) {
+        use rustc_middle::mir::visit::PlaceContext::*;
+
+        // Dereferencing just read the addess of `place.local`.
+        if place.projection.first() == Some(&PlaceElem::Deref) {
+            context = NonMutatingUse(NonMutatingUseContext::Copy);
+        }
+
+        self.visit_local(place.local, context, loc);
+        self.visit_projection(place.as_ref(), context, loc);
+    }
+
+    fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
+        use rustc_middle::mir::visit::PlaceContext::*;
+        match context {
+            // These are just stores, where the storing is not propagatable, but there may be later
+            // mutations of the same local via `Store`
+            | MutatingUse(MutatingUseContext::Call)
+            | MutatingUse(MutatingUseContext::AsmOutput)
+            | MutatingUse(MutatingUseContext::Deinit)
+            // Actual store that can possibly even propagate a value
+            | MutatingUse(MutatingUseContext::Store)
+            | MutatingUse(MutatingUseContext::SetDiscriminant) => {
+                if !self.found_assignment.insert(local) {
+                    match &mut self.can_const_prop[local] {
+                        // If the local can only get propagated in its own block, then we don't have
+                        // to worry about multiple assignments, as we'll nuke the const state at the
+                        // end of the block anyway, and inside the block we overwrite previous
+                        // states as applicable.
+                        ConstPropMode::OnlyInsideOwnBlock => {}
+                        ConstPropMode::NoPropagation => {}
+                        other @ ConstPropMode::FullConstProp => {
+                            trace!(
+                                "local {:?} can't be propagated because of multiple assignments. Previous state: {:?}",
+                                local, other,
+                            );
+                            *other = ConstPropMode::OnlyInsideOwnBlock;
+                        }
+                    }
+                }
+            }
+            // Reading constants is allowed an arbitrary number of times
+            NonMutatingUse(NonMutatingUseContext::Copy)
+            | NonMutatingUse(NonMutatingUseContext::Move)
+            | NonMutatingUse(NonMutatingUseContext::Inspect)
+            | NonMutatingUse(NonMutatingUseContext::PlaceMention)
+            | NonUse(_) => {}
+
+            // These could be propagated with a smarter analysis or just some careful thinking about
+            // whether they'd be fine right now.
+            MutatingUse(MutatingUseContext::Yield)
+            | MutatingUse(MutatingUseContext::Drop)
+            | MutatingUse(MutatingUseContext::Retag)
+            // These can't ever be propagated under any scheme, as we can't reason about indirect
+            // mutation.
+            | NonMutatingUse(NonMutatingUseContext::SharedBorrow)
+            | NonMutatingUse(NonMutatingUseContext::FakeBorrow)
+            | NonMutatingUse(NonMutatingUseContext::AddressOf)
+            | MutatingUse(MutatingUseContext::Borrow)
+            | MutatingUse(MutatingUseContext::AddressOf) => {
+                trace!("local {:?} can't be propagated because it's used: {:?}", local, context);
+                self.can_const_prop[local] = ConstPropMode::NoPropagation;
+            }
+            MutatingUse(MutatingUseContext::Projection)
+            | NonMutatingUse(NonMutatingUseContext::Projection) => bug!("visit_place should not pass {context:?} for {local:?}"),
+        }
+    }
+}