```
When processing the `let x`, we will add one drop to the scope for
-`x`. The break will then insert a drop for `x`. When we process `let
+`x`. The break will then insert a drop for `x`. When we process `let
y`, we will add another drop (in fact, to a subscope, but let's ignore
that for now); any later drops would also drop `y`.
use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder, CFG};
use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::HirId;
use rustc_index::vec::IndexVec;
use rustc_middle::middle::region;
use rustc_middle::mir::*;
/// The target of an expression that breaks out of a scope
#[derive(Clone, Copy, Debug)]
-crate enum BreakableTarget {
+pub(crate) enum BreakableTarget {
Continue(region::Scope),
Break(region::Scope),
Return,
}
rustc_index::newtype_index! {
- struct DropIdx { .. }
+ struct DropIdx {}
}
const ROOT_NODE: DropIdx = DropIdx::from_u32(0);
blocks: &IndexVec<DropIdx, Option<BasicBlock>>,
) {
for (drop_idx, drop_data) in self.drops.iter_enumerated().rev() {
- let block = if let Some(block) = blocks[drop_idx] {
- block
- } else {
- continue;
- };
+ let Some(block) = blocks[drop_idx] else { continue };
match drop_data.0.kind {
DropKind::Value => {
let terminator = TerminatorKind::Drop {
impl<'a, 'tcx> Builder<'a, 'tcx> {
// Adding and removing scopes
// ==========================
- // Start a breakable scope, which tracks where `continue`, `break` and
- // `return` should branch to.
- crate fn in_breakable_scope<F>(
+
+ /// Start a breakable scope, which tracks where `continue`, `break` and
+ /// `return` should branch to.
+ pub(crate) fn in_breakable_scope<F>(
&mut self,
loop_block: Option<BasicBlock>,
break_destination: Place<'tcx>,
let normal_exit_block = f(self);
let breakable_scope = self.scopes.breakable_scopes.pop().unwrap();
assert!(breakable_scope.region_scope == region_scope);
- let break_block = self.build_exit_tree(breakable_scope.break_drops, None);
+ let break_block =
+ self.build_exit_tree(breakable_scope.break_drops, region_scope, span, None);
if let Some(drops) = breakable_scope.continue_drops {
- self.build_exit_tree(drops, loop_block);
+ self.build_exit_tree(drops, region_scope, span, loop_block);
}
match (normal_exit_block, break_block) {
(Some(block), None) | (None, Some(block)) => block,
///
/// if let Some(x) = a && let Some(y) = b && let Some(z) = c { ... }
///
- /// there are three possible ways the condition can be false and we may have
+ /// There are three possible ways the condition can be false and we may have
/// to drop `x`, `x` and `y`, or neither depending on which binding fails.
/// To handle this correctly we use a `DropTree` in a similar way to a
/// `loop` expression and 'break' out on all of the 'else' paths.
/// - We don't need to keep a stack of scopes in the `Builder` because the
/// 'else' paths will only leave the innermost scope.
/// - This is also used for match guards.
- crate fn in_if_then_scope<F>(
+ pub(crate) fn in_if_then_scope<F>(
&mut self,
region_scope: region::Scope,
+ span: Span,
f: F,
) -> (BasicBlock, BasicBlock)
where
assert!(if_then_scope.region_scope == region_scope);
let else_block = self
- .build_exit_tree(if_then_scope.else_drops, None)
+ .build_exit_tree(if_then_scope.else_drops, region_scope, span, None)
.map_or_else(|| self.cfg.start_new_block(), |else_block_and| unpack!(else_block_and));
(then_block, else_block)
}
- crate fn in_opt_scope<F, R>(
+ pub(crate) fn in_opt_scope<F, R>(
&mut self,
opt_scope: Option<(region::Scope, SourceInfo)>,
f: F,
/// Convenience wrapper that pushes a scope and then executes `f`
/// to build its contents, popping the scope afterwards.
- crate fn in_scope<F, R>(
+ #[instrument(skip(self, f), level = "debug")]
+ pub(crate) fn in_scope<F, R>(
&mut self,
region_scope: (region::Scope, SourceInfo),
lint_level: LintLevel,
where
F: FnOnce(&mut Builder<'a, 'tcx>) -> BlockAnd<R>,
{
- debug!("in_scope(region_scope={:?})", region_scope);
let source_scope = self.source_scope;
- let tcx = self.tcx;
if let LintLevel::Explicit(current_hir_id) = lint_level {
- // Use `maybe_lint_level_root_bounded` with `root_lint_level` as a bound
- // to avoid adding Hir dependences on our parents.
- // We estimate the true lint roots here to avoid creating a lot of source scopes.
-
- let parent_root = tcx.maybe_lint_level_root_bounded(
- self.source_scopes[source_scope].local_data.as_ref().assert_crate_local().lint_root,
- self.hir_id,
- );
- let current_root = tcx.maybe_lint_level_root_bounded(current_hir_id, self.hir_id);
-
- if parent_root != current_root {
- self.source_scope = self.new_source_scope(
- region_scope.1.span,
- LintLevel::Explicit(current_root),
- None,
- );
- }
+ let parent_id =
+ self.source_scopes[source_scope].local_data.as_ref().assert_crate_local().lint_root;
+ self.maybe_new_source_scope(region_scope.1.span, None, current_hir_id, parent_id);
}
self.push_scope(region_scope);
let mut block;
let rv = unpack!(block = f(self));
unpack!(block = self.pop_scope(region_scope, block));
self.source_scope = source_scope;
- debug!("in_scope: exiting region_scope={:?} block={:?}", region_scope, block);
+ debug!(?block);
block.and(rv)
}
/// scope and call `pop_scope` afterwards. Note that these two
/// calls must be paired; using `in_scope` as a convenience
/// wrapper maybe preferable.
- crate fn push_scope(&mut self, region_scope: (region::Scope, SourceInfo)) {
+ pub(crate) fn push_scope(&mut self, region_scope: (region::Scope, SourceInfo)) {
self.scopes.push_scope(region_scope, self.source_scope);
}
/// Pops a scope, which should have region scope `region_scope`,
/// adding any drops onto the end of `block` that are needed.
/// This must match 1-to-1 with `push_scope`.
- crate fn pop_scope(
+ pub(crate) fn pop_scope(
&mut self,
region_scope: (region::Scope, SourceInfo),
mut block: BasicBlock,
}
/// Sets up the drops for breaking from `block` to `target`.
- crate fn break_scope(
+ pub(crate) fn break_scope(
&mut self,
mut block: BasicBlock,
value: Option<&Expr<'tcx>>,
// a Coverage code region can be generated, `continue` needs no `Assign`; but
// without one, the `InstrumentCoverage` MIR pass cannot generate a code region for
// `continue`. Coverage will be missing unless we add a dummy `Assign` to MIR.
- self.add_dummy_assignment(&span, block, source_info);
+ self.add_dummy_assignment(span, block, source_info);
}
}
}
drops.add_entry(block, drop_idx);
- // `build_drop_tree` doesn't have access to our source_info, so we
+ // `build_drop_trees` doesn't have access to our source_info, so we
// create a dummy terminator now. `TerminatorKind::Resume` is used
// because MIR type checking will panic if it hasn't been overwritten.
self.cfg.terminate(block, source_info, TerminatorKind::Resume);
self.cfg.start_new_block().unit()
}
- crate fn break_for_else(
+ pub(crate) fn break_for_else(
&mut self,
block: BasicBlock,
target: region::Scope,
}
drops.add_entry(block, drop_idx);
- // `build_drop_tree` doesn't have access to our source_info, so we
+ // `build_drop_trees` doesn't have access to our source_info, so we
// create a dummy terminator now. `TerminatorKind::Resume` is used
// because MIR type checking will panic if it hasn't been overwritten.
self.cfg.terminate(block, source_info, TerminatorKind::Resume);
// Add a dummy `Assign` statement to the CFG, with the span for the source code's `continue`
// statement.
- fn add_dummy_assignment(&mut self, span: &Span, block: BasicBlock, source_info: SourceInfo) {
- let local_decl = LocalDecl::new(self.tcx.mk_unit(), *span).internal();
+ fn add_dummy_assignment(&mut self, span: Span, block: BasicBlock, source_info: SourceInfo) {
+ let local_decl = LocalDecl::new(self.tcx.mk_unit(), span).internal();
let temp_place = Place::from(self.local_decls.push(local_decl));
self.cfg.push_assign_unit(block, source_info, temp_place, self.tcx);
}
))
}
+ /// Possibly creates a new source scope if `current_root` and `parent_root`
+ /// are different, or if -Zmaximal-hir-to-mir-coverage is enabled.
+ pub(crate) fn maybe_new_source_scope(
+ &mut self,
+ span: Span,
+ safety: Option<Safety>,
+ current_id: HirId,
+ parent_id: HirId,
+ ) {
+ let (current_root, parent_root) =
+ if self.tcx.sess.opts.unstable_opts.maximal_hir_to_mir_coverage {
+ // Some consumers of rustc need to map MIR locations back to HIR nodes. Currently the
+ // the only part of rustc that tracks MIR -> HIR is the `SourceScopeLocalData::lint_root`
+ // field that tracks lint levels for MIR locations. Normally the number of source scopes
+ // is limited to the set of nodes with lint annotations. The -Zmaximal-hir-to-mir-coverage
+ // flag changes this behavior to maximize the number of source scopes, increasing the
+ // granularity of the MIR->HIR mapping.
+ (current_id, parent_id)
+ } else {
+ // Use `maybe_lint_level_root_bounded` with `self.hir_id` as a bound
+ // to avoid adding Hir dependencies on our parents.
+ // We estimate the true lint roots here to avoid creating a lot of source scopes.
+ (
+ self.tcx.maybe_lint_level_root_bounded(current_id, self.hir_id),
+ self.tcx.maybe_lint_level_root_bounded(parent_id, self.hir_id),
+ )
+ };
+
+ if current_root != parent_root {
+ let lint_level = LintLevel::Explicit(current_root);
+ self.source_scope = self.new_source_scope(span, lint_level, safety);
+ }
+ }
+
/// Creates a new source scope, nested in the current one.
- crate fn new_source_scope(
+ pub(crate) fn new_source_scope(
&mut self,
span: Span,
lint_level: LintLevel,
}
/// Given a span and the current source scope, make a SourceInfo.
- crate fn source_info(&self, span: Span) -> SourceInfo {
+ pub(crate) fn source_info(&self, span: Span) -> SourceInfo {
SourceInfo { span, scope: self.source_scope }
}
// Finding scopes
// ==============
+
/// Returns the scope that we should use as the lifetime of an
/// operand. Basically, an operand must live until it is consumed.
/// This is similar to, but not quite the same as, the temporary
/// scope (which can be larger or smaller).
///
/// Consider:
- ///
- /// let x = foo(bar(X, Y));
- ///
+ /// ```ignore (illustrative)
+ /// let x = foo(bar(X, Y));
+ /// ```
/// We wish to pop the storage for X and Y after `bar()` is
/// called, not after the whole `let` is completed.
///
/// As another example, if the second argument diverges:
- ///
- /// foo(Box::new(2), panic!())
- ///
+ /// ```ignore (illustrative)
+ /// foo(Box::new(2), panic!())
+ /// ```
/// We would allocate the box but then free it on the unwinding
/// path; we would also emit a free on the 'success' path from
/// panic, but that will turn out to be removed as dead-code.
- crate fn local_scope(&self) -> region::Scope {
+ pub(crate) fn local_scope(&self) -> region::Scope {
self.scopes.topmost()
}
// Scheduling drops
// ================
- crate fn schedule_drop_storage_and_value(
+
+ pub(crate) fn schedule_drop_storage_and_value(
&mut self,
span: Span,
region_scope: region::Scope,
///
/// When called with `DropKind::Storage`, `place` shouldn't be the return
/// place, or a function parameter.
- crate fn schedule_drop(
+ pub(crate) fn schedule_drop(
&mut self,
span: Span,
region_scope: region::Scope,
///
/// Example: when compiling the call to `foo` here:
///
- /// ```rust
+ /// ```ignore (illustrative)
/// foo(bar(), ...)
/// ```
///
/// dropped). However, if no unwind occurs, then `_X` will be
/// unconditionally consumed by the `call`:
///
- /// ```
+ /// ```ignore (illustrative)
/// bb {
/// ...
/// _R = CALL(foo, _X, ...)
/// However, `_X` is still registered to be dropped, and so if we
/// do nothing else, we would generate a `DROP(_X)` that occurs
/// after the call. This will later be optimized out by the
- /// drop-elaboation code, but in the meantime it can lead to
+ /// drop-elaboration code, but in the meantime it can lead to
/// spurious borrow-check errors -- the problem, ironically, is
/// not the `DROP(_X)` itself, but the (spurious) unwind pathways
/// that it creates. See #64391 for an example.
- crate fn record_operands_moved(&mut self, operands: &[Operand<'tcx>]) {
+ pub(crate) fn record_operands_moved(&mut self, operands: &[Operand<'tcx>]) {
let local_scope = self.local_scope();
let scope = self.scopes.scopes.last_mut().unwrap();
// Other
// =====
+
/// Returns the [DropIdx] for the innermost drop if the function unwound at
/// this point. The `DropIdx` will be created if it doesn't already exist.
fn diverge_cleanup(&mut self) -> DropIdx {
- let is_generator = self.generator_kind.is_some();
- let (uncached_scope, mut cached_drop) = self
- .scopes
- .scopes
+ // It is okay to use dummy span because the getting scope index on the topmost scope
+ // must always succeed.
+ self.diverge_cleanup_target(self.scopes.topmost(), DUMMY_SP)
+ }
+
+ /// This is similar to [diverge_cleanup](Self::diverge_cleanup) except its target is set to
+ /// some ancestor scope instead of the current scope.
+ /// It is possible to unwind to some ancestor scope if some drop panics as
+ /// the program breaks out of a if-then scope.
+ fn diverge_cleanup_target(&mut self, target_scope: region::Scope, span: Span) -> DropIdx {
+ let target = self.scopes.scope_index(target_scope, span);
+ let (uncached_scope, mut cached_drop) = self.scopes.scopes[..=target]
.iter()
.enumerate()
.rev()
})
.unwrap_or((0, ROOT_NODE));
- for scope in &mut self.scopes.scopes[uncached_scope..] {
+ if uncached_scope > target {
+ return cached_drop;
+ }
+
+ let is_generator = self.generator_kind.is_some();
+ for scope in &mut self.scopes.scopes[uncached_scope..=target] {
for drop in &scope.drops {
if is_generator || drop.kind == DropKind::Value {
cached_drop = self.scopes.unwind_drops.add_drop(*drop, cached_drop);
///
/// This path terminates in Resume. The path isn't created until after all
/// of the non-unwind paths in this item have been lowered.
- crate fn diverge_from(&mut self, start: BasicBlock) {
+ pub(crate) fn diverge_from(&mut self, start: BasicBlock) {
debug_assert!(
matches!(
self.cfg.block_data(start).terminator().kind,
TerminatorKind::Assert { .. }
| TerminatorKind::Call { .. }
+ | TerminatorKind::Drop { .. }
| TerminatorKind::DropAndReplace { .. }
| TerminatorKind::FalseUnwind { .. }
+ | TerminatorKind::InlineAsm { .. }
),
"diverge_from called on block with terminator that cannot unwind."
);
/// [TerminatorKind::Yield].
///
/// This path terminates in GeneratorDrop.
- crate fn generator_drop_cleanup(&mut self, yield_block: BasicBlock) {
+ pub(crate) fn generator_drop_cleanup(&mut self, yield_block: BasicBlock) {
debug_assert!(
matches!(
self.cfg.block_data(yield_block).terminator().kind,
}
/// Utility function for *non*-scope code to build their own drops
- crate fn build_drop_and_replace(
+ pub(crate) fn build_drop_and_replace(
&mut self,
block: BasicBlock,
span: Span,
/// Creates an `Assert` terminator and return the success block.
/// If the boolean condition operand is not the expected value,
/// a runtime panic will be caused with the given message.
- crate fn assert(
+ pub(crate) fn assert(
&mut self,
block: BasicBlock,
cond: Operand<'tcx>,
///
/// This is only needed for `match` arm scopes, because they have one
/// entrance per pattern, but only one exit.
- crate fn clear_top_scope(&mut self, region_scope: region::Scope) {
+ pub(crate) fn clear_top_scope(&mut self, region_scope: region::Scope) {
let top_scope = self.scopes.scopes.last_mut().unwrap();
assert_eq!(top_scope.region_scope, region_scope);
fn build_exit_tree(
&mut self,
mut drops: DropTree,
+ else_scope: region::Scope,
+ span: Span,
continue_block: Option<BasicBlock>,
) -> Option<BlockAnd<()>> {
let mut blocks = IndexVec::from_elem(None, &drops.drops);
blocks[ROOT_NODE] = continue_block;
drops.build_mir::<ExitScopes>(&mut self.cfg, &mut blocks);
+ let is_generator = self.generator_kind.is_some();
// Link the exit drop tree to unwind drop tree.
if drops.drops.iter().any(|(drop, _)| drop.kind == DropKind::Value) {
- let unwind_target = self.diverge_cleanup();
+ let unwind_target = self.diverge_cleanup_target(else_scope, span);
let mut unwind_indices = IndexVec::from_elem_n(unwind_target, 1);
for (drop_idx, drop_data) in drops.drops.iter_enumerated().skip(1) {
match drop_data.0.kind {
DropKind::Storage => {
- if self.generator_kind.is_some() {
+ if is_generator {
let unwind_drop = self
.scopes
.unwind_drops
}
/// Build the unwind and generator drop trees.
- crate fn build_drop_trees(&mut self) {
+ pub(crate) fn build_drop_trees(&mut self) {
if self.generator_kind.is_some() {
self.build_generator_drop_trees();
} else {
| TerminatorKind::DropAndReplace { unwind, .. }
| TerminatorKind::FalseUnwind { unwind, .. }
| TerminatorKind::Call { cleanup: unwind, .. }
- | TerminatorKind::Assert { cleanup: unwind, .. } => {
+ | TerminatorKind::Assert { cleanup: unwind, .. }
+ | TerminatorKind::InlineAsm { cleanup: unwind, .. } => {
*unwind = Some(to);
}
TerminatorKind::Goto { .. }
| TerminatorKind::Unreachable
| TerminatorKind::Yield { .. }
| TerminatorKind::GeneratorDrop
- | TerminatorKind::FalseEdge { .. }
- | TerminatorKind::InlineAsm { .. } => {
+ | TerminatorKind::FalseEdge { .. } => {
span_bug!(term.source_info.span, "cannot unwind from {:?}", term.kind)
}
}
projects / rustc.git / blobdiff