bjoernager/rust
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Revert "Simplify unscheduling of drops after moves"

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This reverts commit b766abc88f.
This commit is contained in:
Felix S. Klock II 2021-01-21 22:44:02 -05:00
parent bed69c6134
commit dac354fc32
5 changed files with 80 additions and 31 deletions
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38
compiler/rustc_mir_build/src/build/scope.rs
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@ -83,7 +83,7 @@ that contains only loops and breakable blocks. It tracks where a `break`,
use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder, CFG};
use crate::thir::{Expr, ExprRef, LintLevel};
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::fx::FxHashMap;
use rustc_index::vec::IndexVec;
use rustc_middle::middle::region;
use rustc_middle::mir::*;
@ -120,6 +120,8 @@ struct Scope {
/// end of the vector (top of the stack) first.
drops: Vec<DropData>,
moved_locals: Vec<Local>,
/// The drop index that will drop everything in and below this scope on an
/// unwind path.
cached_unwind_block: Option<DropIdx>,
@ -403,6 +405,7 @@ impl<'tcx> Scopes<'tcx> {
region_scope: region_scope.0,
region_scope_span: region_scope.1.span,
drops: vec![],
moved_locals: vec![],
cached_unwind_block: None,
cached_generator_drop_block: None,
});
@ -890,19 +893,20 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
assert_eq!(scope.region_scope, local_scope, "local scope is not the topmost scope!",);
// look for moves of a local variable, like `MOVE(_X)`
let locals_moved = operands
.iter()
.filter_map(|operand| match operand {
Operand::Copy(_) | Operand::Constant(_) => None,
Operand::Move(place) => place.as_local(),
})
.collect::<FxHashSet<_>>();
let locals_moved = operands.iter().flat_map(|operand| match operand {
Operand::Copy(_) | Operand::Constant(_) => None,
Operand::Move(place) => place.as_local(),
});
// Remove the drops for the moved operands.
scope
.drops
.retain(|drop| drop.kind == DropKind::Storage || !locals_moved.contains(&drop.local));
scope.invalidate_cache();
for local in locals_moved {
// check if we have a Drop for this operand and -- if so
// -- add it to the list of moved operands. Note that this
// local might not have been an operand created for this
// call, it could come from other places too.
if scope.drops.iter().any(|drop| drop.local == local && drop.kind == DropKind::Value) {
scope.moved_locals.push(local);
}
}
}
// Other
@ -1147,6 +1151,14 @@ fn build_scope_drops<'tcx>(
debug_assert_eq!(unwind_drops.drops[unwind_to].0.kind, drop_data.kind);
unwind_to = unwind_drops.drops[unwind_to].1;
// If the operand has been moved, and we are not on an unwind
// path, then don't generate the drop. (We only take this into
// account for non-unwind paths so as not to disturb the
// caching mechanism.)
if scope.moved_locals.iter().any(|&o| o == local) {
continue;
}
unwind_drops.add_entry(block, unwind_to);
let next = cfg.start_new_block();