2018-10-23 02:01:45 -05:00
|
|
|
use crate::utils::{
|
2020-03-09 23:17:15 -05:00
|
|
|
fn_has_unsatisfiable_preds, has_drop, is_copy, match_def_path, match_type, paths, snippet_opt, span_lint_hir,
|
|
|
|
span_lint_hir_and_then, walk_ptrs_ty_depth,
|
2018-10-23 02:01:45 -05:00
|
|
|
};
|
|
|
|
use if_chain::if_chain;
|
2019-10-01 18:02:18 -05:00
|
|
|
use rustc_data_structures::{fx::FxHashMap, transitive_relation::TransitiveRelation};
|
2018-12-29 09:04:45 -06:00
|
|
|
use rustc_errors::Applicability;
|
2020-01-09 01:13:22 -06:00
|
|
|
use rustc_hir::intravisit::FnKind;
|
2020-01-06 10:39:50 -06:00
|
|
|
use rustc_hir::{def_id, Body, FnDecl, HirId};
|
2019-10-01 18:02:18 -05:00
|
|
|
use rustc_index::bit_set::{BitSet, HybridBitSet};
|
2020-01-12 00:08:41 -06:00
|
|
|
use rustc_lint::{LateContext, LateLintPass};
|
2020-03-30 04:02:14 -05:00
|
|
|
use rustc_middle::mir::{
|
|
|
|
self, traversal,
|
|
|
|
visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor as _},
|
|
|
|
};
|
|
|
|
use rustc_middle::ty::{self, fold::TypeVisitor, Ty};
|
2020-02-13 23:42:10 -06:00
|
|
|
use rustc_mir::dataflow::BottomValue;
|
2020-03-27 09:35:25 -05:00
|
|
|
use rustc_mir::dataflow::{Analysis, AnalysisDomain, GenKill, GenKillAnalysis, ResultsCursor};
|
2020-01-11 05:37:08 -06:00
|
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
2020-01-04 04:00:00 -06:00
|
|
|
use rustc_span::source_map::{BytePos, Span};
|
2018-10-23 02:01:45 -05:00
|
|
|
use std::convert::TryFrom;
|
|
|
|
|
2018-10-25 08:02:46 -05:00
|
|
|
macro_rules! unwrap_or_continue {
|
|
|
|
($x:expr) => {
|
|
|
|
match $x {
|
|
|
|
Some(x) => x,
|
|
|
|
None => continue,
|
|
|
|
}
|
|
|
|
};
|
|
|
|
}
|
|
|
|
|
2018-10-23 02:01:45 -05:00
|
|
|
declare_clippy_lint! {
|
2019-12-19 18:07:42 -06:00
|
|
|
/// **What it does:** Checks for a redundant `clone()` (and its relatives) which clones an owned
|
2019-03-05 10:50:33 -06:00
|
|
|
/// value that is going to be dropped without further use.
|
|
|
|
///
|
|
|
|
/// **Why is this bad?** It is not always possible for the compiler to eliminate useless
|
|
|
|
/// allocations and deallocations generated by redundant `clone()`s.
|
|
|
|
///
|
|
|
|
/// **Known problems:**
|
|
|
|
///
|
2019-09-16 10:50:15 -05:00
|
|
|
/// False-negatives: analysis performed by this lint is conservative and limited.
|
2019-03-05 10:50:33 -06:00
|
|
|
///
|
|
|
|
/// **Example:**
|
|
|
|
/// ```rust
|
2019-08-03 14:01:23 -05:00
|
|
|
/// # use std::path::Path;
|
|
|
|
/// # #[derive(Clone)]
|
|
|
|
/// # struct Foo;
|
|
|
|
/// # impl Foo {
|
|
|
|
/// # fn new() -> Self { Foo {} }
|
|
|
|
/// # }
|
|
|
|
/// # fn call(x: Foo) {}
|
2019-03-05 10:50:33 -06:00
|
|
|
/// {
|
|
|
|
/// let x = Foo::new();
|
|
|
|
/// call(x.clone());
|
|
|
|
/// call(x.clone()); // this can just pass `x`
|
|
|
|
/// }
|
|
|
|
///
|
2019-08-03 14:01:23 -05:00
|
|
|
/// ["lorem", "ipsum"].join(" ").to_string();
|
2019-03-05 10:50:33 -06:00
|
|
|
///
|
2019-08-03 14:01:23 -05:00
|
|
|
/// Path::new("/a/b").join("c").to_path_buf();
|
2019-03-05 10:50:33 -06:00
|
|
|
/// ```
|
2018-10-23 02:01:45 -05:00
|
|
|
pub REDUNDANT_CLONE,
|
2019-09-16 10:50:15 -05:00
|
|
|
perf,
|
2018-10-23 02:01:45 -05:00
|
|
|
"`clone()` of an owned value that is going to be dropped immediately"
|
|
|
|
}
|
|
|
|
|
2019-04-08 15:43:55 -05:00
|
|
|
declare_lint_pass!(RedundantClone => [REDUNDANT_CLONE]);
|
2018-10-23 02:01:45 -05:00
|
|
|
|
|
|
|
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RedundantClone {
|
2019-01-13 09:19:02 -06:00
|
|
|
#[allow(clippy::too_many_lines)]
|
2018-10-23 02:01:45 -05:00
|
|
|
fn check_fn(
|
|
|
|
&mut self,
|
|
|
|
cx: &LateContext<'a, 'tcx>,
|
|
|
|
_: FnKind<'tcx>,
|
2019-12-29 22:02:10 -06:00
|
|
|
_: &'tcx FnDecl<'_>,
|
2019-12-22 08:42:41 -06:00
|
|
|
body: &'tcx Body<'_>,
|
2018-10-23 02:01:45 -05:00
|
|
|
_: Span,
|
2019-02-20 04:11:11 -06:00
|
|
|
_: HirId,
|
2018-10-23 02:01:45 -05:00
|
|
|
) {
|
2018-12-07 18:56:03 -06:00
|
|
|
let def_id = cx.tcx.hir().body_owner_def_id(body.id());
|
2020-03-09 23:17:15 -05:00
|
|
|
|
|
|
|
// Building MIR for `fn`s with unsatisfiable preds results in ICE.
|
|
|
|
if fn_has_unsatisfiable_preds(cx, def_id) {
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
2018-10-23 02:01:45 -05:00
|
|
|
let mir = cx.tcx.optimized_mir(def_id);
|
2019-12-02 13:39:40 -06:00
|
|
|
let mir_read_only = mir.unwrap_read_only();
|
2018-10-23 02:01:45 -05:00
|
|
|
|
2020-02-13 23:42:10 -06:00
|
|
|
let maybe_storage_live_result = MaybeStorageLive
|
|
|
|
.into_engine(cx.tcx, mir, def_id)
|
|
|
|
.iterate_to_fixpoint()
|
|
|
|
.into_results_cursor(mir);
|
2019-09-16 10:50:15 -05:00
|
|
|
let mut possible_borrower = {
|
|
|
|
let mut vis = PossibleBorrowerVisitor::new(cx, mir);
|
2020-03-30 00:34:19 -05:00
|
|
|
vis.visit_body(&mir_read_only);
|
2019-09-16 10:50:15 -05:00
|
|
|
vis.into_map(cx, maybe_storage_live_result)
|
|
|
|
};
|
|
|
|
|
2018-10-23 02:01:45 -05:00
|
|
|
for (bb, bbdata) in mir.basic_blocks().iter_enumerated() {
|
2018-10-25 11:27:28 -05:00
|
|
|
let terminator = bbdata.terminator();
|
2018-10-23 02:01:45 -05:00
|
|
|
|
2019-08-19 11:30:32 -05:00
|
|
|
if terminator.source_info.span.from_expansion() {
|
2018-10-25 13:07:29 -05:00
|
|
|
continue;
|
|
|
|
}
|
|
|
|
|
2018-10-23 02:01:45 -05:00
|
|
|
// Give up on loops
|
|
|
|
if terminator.successors().any(|s| *s == bb) {
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
|
2020-03-12 10:31:09 -05:00
|
|
|
let (fn_def_id, arg, arg_ty, clone_ret) =
|
|
|
|
unwrap_or_continue!(is_call_with_ref_arg(cx, mir, &terminator.kind));
|
2018-10-23 02:01:45 -05:00
|
|
|
|
2019-05-17 16:53:54 -05:00
|
|
|
let from_borrow = match_def_path(cx, fn_def_id, &paths::CLONE_TRAIT_METHOD)
|
|
|
|
|| match_def_path(cx, fn_def_id, &paths::TO_OWNED_METHOD)
|
2019-05-17 17:58:25 -05:00
|
|
|
|| (match_def_path(cx, fn_def_id, &paths::TO_STRING_METHOD) && match_type(cx, arg_ty, &paths::STRING));
|
2018-10-23 02:01:45 -05:00
|
|
|
|
|
|
|
let from_deref = !from_borrow
|
2019-05-17 16:53:54 -05:00
|
|
|
&& (match_def_path(cx, fn_def_id, &paths::PATH_TO_PATH_BUF)
|
|
|
|
|| match_def_path(cx, fn_def_id, &paths::OS_STR_TO_OS_STRING));
|
2018-10-23 02:01:45 -05:00
|
|
|
|
|
|
|
if !from_borrow && !from_deref {
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
|
2019-09-30 02:16:09 -05:00
|
|
|
// `{ cloned = &arg; clone(move cloned); }` or `{ cloned = &arg; to_path_buf(cloned); }`
|
2019-09-16 10:50:15 -05:00
|
|
|
let (cloned, cannot_move_out) = unwrap_or_continue!(find_stmt_assigns_to(cx, mir, arg, from_borrow, bb));
|
|
|
|
|
|
|
|
let loc = mir::Location {
|
|
|
|
block: bb,
|
|
|
|
statement_index: bbdata.statements.len(),
|
|
|
|
};
|
|
|
|
|
2020-03-12 10:31:09 -05:00
|
|
|
// `Local` to be cloned, and a local of `clone` call's destination
|
|
|
|
let (local, ret_local) = if from_borrow {
|
2019-09-30 02:16:09 -05:00
|
|
|
// `res = clone(arg)` can be turned into `res = move arg;`
|
|
|
|
// if `arg` is the only borrow of `cloned` at this point.
|
|
|
|
|
|
|
|
if cannot_move_out || !possible_borrower.only_borrowers(&[arg], cloned, loc) {
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
|
2020-03-12 10:31:09 -05:00
|
|
|
(cloned, clone_ret)
|
2019-09-30 02:16:09 -05:00
|
|
|
} else {
|
|
|
|
// `arg` is a reference as it is `.deref()`ed in the previous block.
|
|
|
|
// Look into the predecessor block and find out the source of deref.
|
2018-10-23 02:01:45 -05:00
|
|
|
|
2019-12-02 13:39:40 -06:00
|
|
|
let ps = mir_read_only.predecessors_for(bb);
|
2018-10-25 08:02:46 -05:00
|
|
|
if ps.len() != 1 {
|
|
|
|
continue;
|
|
|
|
}
|
2018-10-25 11:27:28 -05:00
|
|
|
let pred_terminator = mir[ps[0]].terminator();
|
2018-10-25 08:02:46 -05:00
|
|
|
|
2019-09-30 02:16:09 -05:00
|
|
|
// receiver of the `deref()` call
|
2020-03-12 10:31:09 -05:00
|
|
|
let (pred_arg, deref_clone_ret) = if_chain! {
|
|
|
|
if let Some((pred_fn_def_id, pred_arg, pred_arg_ty, res)) =
|
2018-10-25 08:02:46 -05:00
|
|
|
is_call_with_ref_arg(cx, mir, &pred_terminator.kind);
|
2020-03-12 10:31:09 -05:00
|
|
|
if res == cloned;
|
2019-05-17 16:53:54 -05:00
|
|
|
if match_def_path(cx, pred_fn_def_id, &paths::DEREF_TRAIT_METHOD);
|
|
|
|
if match_type(cx, pred_arg_ty, &paths::PATH_BUF)
|
|
|
|
|| match_type(cx, pred_arg_ty, &paths::OS_STRING);
|
2018-10-23 02:01:45 -05:00
|
|
|
then {
|
2020-03-12 10:31:09 -05:00
|
|
|
(pred_arg, res)
|
2018-10-23 02:01:45 -05:00
|
|
|
} else {
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
};
|
|
|
|
|
2019-09-16 10:50:15 -05:00
|
|
|
let (local, cannot_move_out) =
|
|
|
|
unwrap_or_continue!(find_stmt_assigns_to(cx, mir, pred_arg, true, ps[0]));
|
|
|
|
let loc = mir::Location {
|
|
|
|
block: bb,
|
|
|
|
statement_index: mir.basic_blocks()[bb].statements.len(),
|
|
|
|
};
|
2019-09-30 02:16:09 -05:00
|
|
|
|
|
|
|
// This can be turned into `res = move local` if `arg` and `cloned` are not borrowed
|
|
|
|
// at the last statement:
|
|
|
|
//
|
|
|
|
// ```
|
|
|
|
// pred_arg = &local;
|
|
|
|
// cloned = deref(pred_arg);
|
|
|
|
// arg = &cloned;
|
|
|
|
// StorageDead(pred_arg);
|
|
|
|
// res = to_path_buf(cloned);
|
|
|
|
// ```
|
2019-09-28 06:29:35 -05:00
|
|
|
if cannot_move_out || !possible_borrower.only_borrowers(&[arg, cloned], local, loc) {
|
2018-12-09 05:19:21 -06:00
|
|
|
continue;
|
|
|
|
}
|
2019-09-30 02:16:09 -05:00
|
|
|
|
2020-03-12 10:31:09 -05:00
|
|
|
(local, deref_clone_ret)
|
2018-10-23 02:01:45 -05:00
|
|
|
};
|
|
|
|
|
2020-03-12 10:54:40 -05:00
|
|
|
let is_temp = mir_read_only.local_kind(ret_local) == mir::LocalKind::Temp;
|
|
|
|
|
|
|
|
// 1. `local` can be moved out if it is not used later.
|
2020-03-12 11:25:18 -05:00
|
|
|
// 2. If `ret_local` is a temporary and is neither consumed nor mutated, we can remove this `clone`
|
|
|
|
// call anyway.
|
|
|
|
let (used, consumed_or_mutated) = traversal::ReversePostorder::new(&mir, bb).skip(1).fold(
|
2020-03-12 10:54:40 -05:00
|
|
|
(false, !is_temp),
|
2020-03-12 10:31:09 -05:00
|
|
|
|(used, consumed), (tbb, tdata)| {
|
|
|
|
// Short-circuit
|
|
|
|
if (used && consumed) ||
|
|
|
|
// Give up on loops
|
|
|
|
tdata.terminator().successors().any(|s| *s == bb)
|
|
|
|
{
|
|
|
|
return (true, true);
|
|
|
|
}
|
2018-10-23 02:01:45 -05:00
|
|
|
|
2020-03-12 10:31:09 -05:00
|
|
|
let mut vis = LocalUseVisitor {
|
|
|
|
used: (local, false),
|
2020-03-12 11:25:18 -05:00
|
|
|
consumed_or_mutated: (ret_local, false),
|
2020-03-12 10:31:09 -05:00
|
|
|
};
|
|
|
|
vis.visit_basic_block_data(tbb, tdata);
|
2020-03-12 11:25:18 -05:00
|
|
|
(used || vis.used.1, consumed || vis.consumed_or_mutated.1)
|
2020-03-12 10:31:09 -05:00
|
|
|
},
|
|
|
|
);
|
2018-10-23 02:01:45 -05:00
|
|
|
|
2020-03-12 11:25:18 -05:00
|
|
|
if !used || !consumed_or_mutated {
|
2018-10-23 02:01:45 -05:00
|
|
|
let span = terminator.source_info.span;
|
2019-12-02 02:51:35 -06:00
|
|
|
let scope = terminator.source_info.scope;
|
2019-12-02 04:50:46 -06:00
|
|
|
let node = mir.source_scopes[scope]
|
|
|
|
.local_data
|
|
|
|
.as_ref()
|
|
|
|
.assert_crate_local()
|
|
|
|
.lint_root;
|
2018-10-25 07:08:32 -05:00
|
|
|
|
2018-10-23 02:01:45 -05:00
|
|
|
if_chain! {
|
|
|
|
if let Some(snip) = snippet_opt(cx, span);
|
|
|
|
if let Some(dot) = snip.rfind('.');
|
|
|
|
then {
|
|
|
|
let sugg_span = span.with_lo(
|
|
|
|
span.lo() + BytePos(u32::try_from(dot).unwrap())
|
|
|
|
);
|
2019-09-09 21:56:34 -05:00
|
|
|
let mut app = Applicability::MaybeIncorrect;
|
2019-09-30 02:16:09 -05:00
|
|
|
|
2019-09-09 21:56:34 -05:00
|
|
|
let mut call_snip = &snip[dot + 1..];
|
2019-09-30 02:16:09 -05:00
|
|
|
// Machine applicable when `call_snip` looks like `foobar()`
|
2019-09-09 21:56:34 -05:00
|
|
|
if call_snip.ends_with("()") {
|
|
|
|
call_snip = call_snip[..call_snip.len()-2].trim();
|
|
|
|
if call_snip.as_bytes().iter().all(|b| b.is_ascii_alphabetic() || *b == b'_') {
|
|
|
|
app = Applicability::MachineApplicable;
|
|
|
|
}
|
|
|
|
}
|
2018-10-23 02:01:45 -05:00
|
|
|
|
2019-03-12 02:01:21 -05:00
|
|
|
span_lint_hir_and_then(cx, REDUNDANT_CLONE, node, sugg_span, "redundant clone", |db| {
|
2019-01-27 06:33:56 -06:00
|
|
|
db.span_suggestion(
|
2018-10-23 02:01:45 -05:00
|
|
|
sugg_span,
|
|
|
|
"remove this",
|
|
|
|
String::new(),
|
2019-09-09 21:56:34 -05:00
|
|
|
app,
|
2018-10-23 02:01:45 -05:00
|
|
|
);
|
2020-03-12 10:31:09 -05:00
|
|
|
if used {
|
|
|
|
db.span_note(
|
|
|
|
span,
|
2020-03-12 11:25:18 -05:00
|
|
|
"cloned value is neither consumed nor mutated",
|
2020-03-12 10:31:09 -05:00
|
|
|
);
|
|
|
|
} else {
|
|
|
|
db.span_note(
|
|
|
|
span.with_hi(span.lo() + BytePos(u32::try_from(dot).unwrap())),
|
|
|
|
"this value is dropped without further use",
|
|
|
|
);
|
|
|
|
}
|
2018-10-23 02:01:45 -05:00
|
|
|
});
|
|
|
|
} else {
|
2019-03-12 02:01:21 -05:00
|
|
|
span_lint_hir(cx, REDUNDANT_CLONE, node, span, "redundant clone");
|
2018-10-23 02:01:45 -05:00
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2018-10-25 08:02:46 -05:00
|
|
|
/// If `kind` is `y = func(x: &T)` where `T: !Copy`, returns `(DefId of func, x, T, y)`.
|
|
|
|
fn is_call_with_ref_arg<'tcx>(
|
|
|
|
cx: &LateContext<'_, 'tcx>,
|
2019-05-28 17:41:34 -05:00
|
|
|
mir: &'tcx mir::Body<'tcx>,
|
2018-10-25 08:02:46 -05:00
|
|
|
kind: &'tcx mir::TerminatorKind<'tcx>,
|
2020-03-12 10:31:09 -05:00
|
|
|
) -> Option<(def_id::DefId, mir::Local, Ty<'tcx>, mir::Local)> {
|
2018-10-25 08:02:46 -05:00
|
|
|
if_chain! {
|
2019-09-16 10:50:15 -05:00
|
|
|
if let mir::TerminatorKind::Call { func, args, destination, .. } = kind;
|
2018-10-25 08:02:46 -05:00
|
|
|
if args.len() == 1;
|
2020-01-11 12:41:54 -06:00
|
|
|
if let mir::Operand::Move(mir::Place { local, .. }) = &args[0];
|
2019-09-26 04:03:36 -05:00
|
|
|
if let ty::FnDef(def_id, _) = func.ty(&*mir, cx.tcx).kind;
|
2018-10-25 08:02:46 -05:00
|
|
|
if let (inner_ty, 1) = walk_ptrs_ty_depth(args[0].ty(&*mir, cx.tcx));
|
|
|
|
if !is_copy(cx, inner_ty);
|
|
|
|
then {
|
2020-03-12 10:31:09 -05:00
|
|
|
Some((def_id, *local, inner_ty, destination.as_ref().map(|(dest, _)| dest)?.as_local()?))
|
2018-10-25 08:02:46 -05:00
|
|
|
} else {
|
|
|
|
None
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2018-12-09 05:19:21 -06:00
|
|
|
type CannotMoveOut = bool;
|
|
|
|
|
2018-12-10 00:48:34 -06:00
|
|
|
/// Finds the first `to = (&)from`, and returns
|
2019-09-16 10:50:15 -05:00
|
|
|
/// ``Some((from, whether `from` cannot be moved out))``.
|
|
|
|
fn find_stmt_assigns_to<'tcx>(
|
2018-12-09 05:19:21 -06:00
|
|
|
cx: &LateContext<'_, 'tcx>,
|
2019-05-28 17:41:34 -05:00
|
|
|
mir: &mir::Body<'tcx>,
|
2019-09-16 10:50:15 -05:00
|
|
|
to_local: mir::Local,
|
2018-10-25 08:02:46 -05:00
|
|
|
by_ref: bool,
|
2019-09-16 10:50:15 -05:00
|
|
|
bb: mir::BasicBlock,
|
2018-12-09 05:19:21 -06:00
|
|
|
) -> Option<(mir::Local, CannotMoveOut)> {
|
2019-09-16 10:50:15 -05:00
|
|
|
let rvalue = mir.basic_blocks()[bb].statements.iter().rev().find_map(|stmt| {
|
2020-01-11 12:41:54 -06:00
|
|
|
if let mir::StatementKind::Assign(box (mir::Place { local, .. }, v)) = &stmt.kind {
|
2019-09-16 10:50:15 -05:00
|
|
|
return if *local == to_local { Some(v) } else { None };
|
|
|
|
}
|
2018-10-25 08:02:46 -05:00
|
|
|
|
2019-09-16 10:50:15 -05:00
|
|
|
None
|
|
|
|
})?;
|
|
|
|
|
|
|
|
match (by_ref, &*rvalue) {
|
|
|
|
(true, mir::Rvalue::Ref(_, _, place)) | (false, mir::Rvalue::Use(mir::Operand::Copy(place))) => {
|
2020-01-11 14:20:18 -06:00
|
|
|
base_local_and_movability(cx, mir, *place)
|
2019-09-16 10:50:15 -05:00
|
|
|
},
|
2020-01-07 22:59:58 -06:00
|
|
|
(false, mir::Rvalue::Ref(_, _, place)) => {
|
|
|
|
if let [mir::ProjectionElem::Deref] = place.as_ref().projection {
|
2020-01-11 14:20:18 -06:00
|
|
|
base_local_and_movability(cx, mir, *place)
|
2020-01-07 22:59:58 -06:00
|
|
|
} else {
|
|
|
|
None
|
|
|
|
}
|
|
|
|
},
|
2019-09-16 10:50:15 -05:00
|
|
|
_ => None,
|
|
|
|
}
|
2018-10-25 08:02:46 -05:00
|
|
|
}
|
|
|
|
|
2018-12-10 00:48:34 -06:00
|
|
|
/// Extracts and returns the undermost base `Local` of given `place`. Returns `place` itself
|
|
|
|
/// if it is already a `Local`.
|
|
|
|
///
|
|
|
|
/// Also reports whether given `place` cannot be moved out.
|
|
|
|
fn base_local_and_movability<'tcx>(
|
2018-12-09 05:19:21 -06:00
|
|
|
cx: &LateContext<'_, 'tcx>,
|
2019-05-28 17:41:34 -05:00
|
|
|
mir: &mir::Body<'tcx>,
|
2020-01-11 14:20:18 -06:00
|
|
|
place: mir::Place<'tcx>,
|
2018-12-09 05:19:21 -06:00
|
|
|
) -> Option<(mir::Local, CannotMoveOut)> {
|
2020-03-30 04:02:14 -05:00
|
|
|
use rustc_middle::mir::PlaceRef;
|
2018-12-09 05:19:21 -06:00
|
|
|
|
2018-12-10 00:48:34 -06:00
|
|
|
// Dereference. You cannot move things out from a borrowed value.
|
2018-12-09 05:19:21 -06:00
|
|
|
let mut deref = false;
|
2018-12-10 00:48:34 -06:00
|
|
|
// Accessing a field of an ADT that has `Drop`. Moving the field out will cause E0509.
|
2018-12-09 05:19:21 -06:00
|
|
|
let mut field = false;
|
|
|
|
|
2020-01-11 12:41:54 -06:00
|
|
|
let PlaceRef { local, mut projection } = place.as_ref();
|
|
|
|
while let [base @ .., elem] = projection {
|
|
|
|
projection = base;
|
|
|
|
deref |= matches!(elem, mir::ProjectionElem::Deref);
|
|
|
|
field |= matches!(elem, mir::ProjectionElem::Field(..))
|
|
|
|
&& has_drop(cx, mir::Place::ty_from(local, projection, &mir.local_decls, cx.tcx).ty);
|
2018-12-09 05:19:21 -06:00
|
|
|
}
|
2020-01-11 12:41:54 -06:00
|
|
|
|
2020-01-29 02:15:56 -06:00
|
|
|
Some((local, deref || field))
|
2018-12-09 05:19:21 -06:00
|
|
|
}
|
|
|
|
|
2018-10-23 02:01:45 -05:00
|
|
|
struct LocalUseVisitor {
|
2020-03-12 10:31:09 -05:00
|
|
|
used: (mir::Local, bool),
|
2020-03-12 11:25:18 -05:00
|
|
|
consumed_or_mutated: (mir::Local, bool),
|
2018-10-23 02:01:45 -05:00
|
|
|
}
|
|
|
|
|
|
|
|
impl<'tcx> mir::visit::Visitor<'tcx> for LocalUseVisitor {
|
2018-10-25 06:33:40 -05:00
|
|
|
fn visit_basic_block_data(&mut self, block: mir::BasicBlock, data: &mir::BasicBlockData<'tcx>) {
|
2018-10-25 11:27:28 -05:00
|
|
|
let statements = &data.statements;
|
2018-10-25 06:33:40 -05:00
|
|
|
for (statement_index, statement) in statements.iter().enumerate() {
|
2019-04-30 00:31:39 -05:00
|
|
|
self.visit_statement(statement, mir::Location { block, statement_index });
|
2018-10-25 06:33:40 -05:00
|
|
|
}
|
|
|
|
|
2018-10-25 11:27:28 -05:00
|
|
|
self.visit_terminator(
|
|
|
|
data.terminator(),
|
|
|
|
mir::Location {
|
2018-10-25 06:33:40 -05:00
|
|
|
block,
|
2018-10-25 11:27:28 -05:00
|
|
|
statement_index: statements.len(),
|
|
|
|
},
|
|
|
|
);
|
2018-10-23 02:01:45 -05:00
|
|
|
}
|
|
|
|
|
2020-03-12 12:06:47 -05:00
|
|
|
fn visit_place(&mut self, place: &mir::Place<'tcx>, ctx: PlaceContext, _: mir::Location) {
|
|
|
|
let local = place.local;
|
|
|
|
|
|
|
|
if local == self.used.0
|
2020-03-12 10:31:09 -05:00
|
|
|
&& !matches!(ctx, PlaceContext::MutatingUse(MutatingUseContext::Drop) | PlaceContext::NonUse(_))
|
|
|
|
{
|
|
|
|
self.used.1 = true;
|
2018-10-23 02:01:45 -05:00
|
|
|
}
|
|
|
|
|
2020-03-12 12:06:47 -05:00
|
|
|
if local == self.consumed_or_mutated.0 {
|
2020-03-12 11:25:18 -05:00
|
|
|
match ctx {
|
|
|
|
PlaceContext::NonMutatingUse(NonMutatingUseContext::Move)
|
|
|
|
| PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
|
|
|
|
self.consumed_or_mutated.1 = true;
|
|
|
|
},
|
|
|
|
_ => {},
|
|
|
|
}
|
2018-10-23 02:01:45 -05:00
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
2019-09-16 10:50:15 -05:00
|
|
|
|
2019-09-30 02:16:09 -05:00
|
|
|
/// Determines liveness of each local purely based on `StorageLive`/`Dead`.
|
2019-09-16 10:50:15 -05:00
|
|
|
#[derive(Copy, Clone)]
|
2020-02-13 23:42:10 -06:00
|
|
|
struct MaybeStorageLive;
|
2019-09-16 10:50:15 -05:00
|
|
|
|
2020-02-13 23:42:10 -06:00
|
|
|
impl<'tcx> AnalysisDomain<'tcx> for MaybeStorageLive {
|
2019-09-16 10:50:15 -05:00
|
|
|
type Idx = mir::Local;
|
2020-02-13 23:42:10 -06:00
|
|
|
const NAME: &'static str = "maybe_storage_live";
|
|
|
|
|
|
|
|
fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize {
|
|
|
|
body.local_decls.len()
|
2019-09-16 10:50:15 -05:00
|
|
|
}
|
|
|
|
|
2020-02-13 23:42:10 -06:00
|
|
|
fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut BitSet<Self::Idx>) {
|
|
|
|
for arg in body.args_iter() {
|
|
|
|
state.insert(arg);
|
2019-09-16 10:50:15 -05:00
|
|
|
}
|
|
|
|
}
|
2020-02-13 23:42:10 -06:00
|
|
|
}
|
2019-09-16 10:50:15 -05:00
|
|
|
|
2020-02-13 23:42:10 -06:00
|
|
|
impl<'tcx> GenKillAnalysis<'tcx> for MaybeStorageLive {
|
|
|
|
fn statement_effect(&self, trans: &mut impl GenKill<Self::Idx>, stmt: &mir::Statement<'tcx>, _: mir::Location) {
|
2019-09-16 10:50:15 -05:00
|
|
|
match stmt.kind {
|
|
|
|
mir::StatementKind::StorageLive(l) => trans.gen(l),
|
|
|
|
mir::StatementKind::StorageDead(l) => trans.kill(l),
|
|
|
|
_ => (),
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2020-02-13 23:42:10 -06:00
|
|
|
fn terminator_effect(
|
|
|
|
&self,
|
|
|
|
_trans: &mut impl GenKill<Self::Idx>,
|
|
|
|
_terminator: &mir::Terminator<'tcx>,
|
|
|
|
_loc: mir::Location,
|
|
|
|
) {
|
|
|
|
}
|
2019-09-16 10:50:15 -05:00
|
|
|
|
2020-02-13 23:42:10 -06:00
|
|
|
fn call_return_effect(
|
2019-09-16 10:50:15 -05:00
|
|
|
&self,
|
2020-02-13 23:42:10 -06:00
|
|
|
_in_out: &mut impl GenKill<Self::Idx>,
|
|
|
|
_block: mir::BasicBlock,
|
|
|
|
_func: &mir::Operand<'tcx>,
|
|
|
|
_args: &[mir::Operand<'tcx>],
|
2020-04-01 12:42:15 -05:00
|
|
|
_return_place: mir::Place<'tcx>,
|
2019-09-16 10:50:15 -05:00
|
|
|
) {
|
|
|
|
// Nothing to do when a call returns successfully
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2020-02-13 23:42:10 -06:00
|
|
|
impl BottomValue for MaybeStorageLive {
|
2019-09-16 10:50:15 -05:00
|
|
|
/// bottom = dead
|
|
|
|
const BOTTOM_VALUE: bool = false;
|
|
|
|
}
|
|
|
|
|
2019-09-30 02:16:09 -05:00
|
|
|
/// Collects the possible borrowers of each local.
|
|
|
|
/// For example, `b = &a; c = &a;` will make `b` and (transitively) `c`
|
|
|
|
/// possible borrowers of `a`.
|
2019-09-16 10:50:15 -05:00
|
|
|
struct PossibleBorrowerVisitor<'a, 'tcx> {
|
|
|
|
possible_borrower: TransitiveRelation<mir::Local>,
|
|
|
|
body: &'a mir::Body<'tcx>,
|
|
|
|
cx: &'a LateContext<'a, 'tcx>,
|
|
|
|
}
|
|
|
|
|
|
|
|
impl<'a, 'tcx> PossibleBorrowerVisitor<'a, 'tcx> {
|
|
|
|
fn new(cx: &'a LateContext<'a, 'tcx>, body: &'a mir::Body<'tcx>) -> Self {
|
|
|
|
Self {
|
|
|
|
possible_borrower: TransitiveRelation::default(),
|
|
|
|
cx,
|
|
|
|
body,
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
fn into_map(
|
|
|
|
self,
|
|
|
|
cx: &LateContext<'a, 'tcx>,
|
2020-02-13 23:42:10 -06:00
|
|
|
maybe_live: ResultsCursor<'tcx, 'tcx, MaybeStorageLive>,
|
2020-02-13 23:07:06 -06:00
|
|
|
) -> PossibleBorrowerMap<'a, 'tcx> {
|
2019-09-16 10:50:15 -05:00
|
|
|
let mut map = FxHashMap::default();
|
|
|
|
for row in (1..self.body.local_decls.len()).map(mir::Local::from_usize) {
|
|
|
|
if is_copy(cx, self.body.local_decls[row].ty) {
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
|
|
|
|
let borrowers = self.possible_borrower.reachable_from(&row);
|
|
|
|
if !borrowers.is_empty() {
|
|
|
|
let mut bs = HybridBitSet::new_empty(self.body.local_decls.len());
|
|
|
|
for &c in borrowers {
|
|
|
|
if c != mir::Local::from_usize(0) {
|
|
|
|
bs.insert(c);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
if !bs.is_empty() {
|
|
|
|
map.insert(row, bs);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
let bs = BitSet::new_empty(self.body.local_decls.len());
|
2020-02-13 23:07:06 -06:00
|
|
|
PossibleBorrowerMap {
|
2019-09-16 10:50:15 -05:00
|
|
|
map,
|
2020-02-13 23:42:10 -06:00
|
|
|
maybe_live,
|
2019-09-16 10:50:15 -05:00
|
|
|
bitset: (bs.clone(), bs),
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
impl<'a, 'tcx> mir::visit::Visitor<'tcx> for PossibleBorrowerVisitor<'a, 'tcx> {
|
|
|
|
fn visit_assign(&mut self, place: &mir::Place<'tcx>, rvalue: &mir::Rvalue<'_>, _location: mir::Location) {
|
2020-01-11 12:41:54 -06:00
|
|
|
let lhs = place.local;
|
|
|
|
match rvalue {
|
|
|
|
mir::Rvalue::Ref(_, _, borrowed) => {
|
|
|
|
self.possible_borrower.add(borrowed.local, lhs);
|
|
|
|
},
|
|
|
|
other => {
|
|
|
|
if !ContainsRegion.visit_ty(place.ty(&self.body.local_decls, self.cx.tcx).ty) {
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
rvalue_locals(other, |rhs| {
|
|
|
|
if lhs != rhs {
|
|
|
|
self.possible_borrower.add(rhs, lhs);
|
2019-09-16 10:50:15 -05:00
|
|
|
}
|
2020-01-11 12:41:54 -06:00
|
|
|
});
|
|
|
|
},
|
2019-09-16 10:50:15 -05:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
fn visit_terminator(&mut self, terminator: &mir::Terminator<'_>, _loc: mir::Location) {
|
|
|
|
if let mir::TerminatorKind::Call {
|
|
|
|
args,
|
2020-01-11 12:41:54 -06:00
|
|
|
destination: Some((mir::Place { local: dest, .. }, _)),
|
2019-09-16 10:50:15 -05:00
|
|
|
..
|
|
|
|
} = &terminator.kind
|
|
|
|
{
|
2019-09-30 02:16:09 -05:00
|
|
|
// If the call returns something with lifetimes,
|
2019-09-16 10:50:15 -05:00
|
|
|
// let's conservatively assume the returned value contains lifetime of all the arguments.
|
2019-09-30 02:16:09 -05:00
|
|
|
// For example, given `let y: Foo<'a> = foo(x)`, `y` is considered to be a possible borrower of `x`.
|
|
|
|
if !ContainsRegion.visit_ty(&self.body.local_decls[*dest].ty) {
|
2019-09-16 10:50:15 -05:00
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
|
|
|
for op in args {
|
|
|
|
match op {
|
|
|
|
mir::Operand::Copy(p) | mir::Operand::Move(p) => {
|
2020-01-11 12:41:54 -06:00
|
|
|
self.possible_borrower.add(p.local, *dest);
|
2019-09-16 10:50:15 -05:00
|
|
|
},
|
|
|
|
_ => (),
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
struct ContainsRegion;
|
|
|
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impl TypeVisitor<'_> for ContainsRegion {
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fn visit_region(&mut self, _: ty::Region<'_>) -> bool {
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true
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}
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}
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fn rvalue_locals(rvalue: &mir::Rvalue<'_>, mut visit: impl FnMut(mir::Local)) {
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2020-03-30 04:02:14 -05:00
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use rustc_middle::mir::Rvalue::{Aggregate, BinaryOp, Cast, CheckedBinaryOp, Repeat, UnaryOp, Use};
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2019-09-16 10:50:15 -05:00
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let mut visit_op = |op: &mir::Operand<'_>| match op {
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2020-01-11 12:41:54 -06:00
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mir::Operand::Copy(p) | mir::Operand::Move(p) => visit(p.local),
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2019-09-16 10:50:15 -05:00
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_ => (),
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};
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match rvalue {
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Use(op) | Repeat(op, _) | Cast(_, op, _) | UnaryOp(_, op) => visit_op(op),
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Aggregate(_, ops) => ops.iter().for_each(visit_op),
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BinaryOp(_, lhs, rhs) | CheckedBinaryOp(_, lhs, rhs) => {
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visit_op(lhs);
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visit_op(rhs);
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},
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_ => (),
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}
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}
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2019-09-30 02:16:09 -05:00
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/// Result of `PossibleBorrowerVisitor`.
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2020-02-13 23:07:06 -06:00
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struct PossibleBorrowerMap<'a, 'tcx> {
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2019-09-30 02:16:09 -05:00
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/// Mapping `Local -> its possible borrowers`
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2019-09-16 10:50:15 -05:00
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map: FxHashMap<mir::Local, HybridBitSet<mir::Local>>,
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2020-02-13 23:42:10 -06:00
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maybe_live: ResultsCursor<'a, 'tcx, MaybeStorageLive>,
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2019-09-28 06:29:35 -05:00
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// Caches to avoid allocation of `BitSet` on every query
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2019-09-16 10:50:15 -05:00
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bitset: (BitSet<mir::Local>, BitSet<mir::Local>),
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}
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2020-02-13 23:07:06 -06:00
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impl PossibleBorrowerMap<'_, '_> {
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2019-09-30 02:16:09 -05:00
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/// Returns true if the set of borrowers of `borrowed` living at `at` matches with `borrowers`.
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2019-09-28 06:29:35 -05:00
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fn only_borrowers(&mut self, borrowers: &[mir::Local], borrowed: mir::Local, at: mir::Location) -> bool {
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2020-02-13 23:42:10 -06:00
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self.maybe_live.seek_after(at);
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2019-09-16 10:50:15 -05:00
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self.bitset.0.clear();
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let maybe_live = &mut self.maybe_live;
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2019-09-28 06:29:35 -05:00
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if let Some(bitset) = self.map.get(&borrowed) {
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for b in bitset.iter().filter(move |b| maybe_live.contains(*b)) {
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self.bitset.0.insert(b);
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}
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} else {
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return false;
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2019-09-16 10:50:15 -05:00
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}
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self.bitset.1.clear();
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for b in borrowers {
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self.bitset.1.insert(*b);
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}
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2019-09-28 06:29:35 -05:00
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self.bitset.0 == self.bitset.1
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2019-09-16 10:50:15 -05:00
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}
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}
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