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Auto merge of #43576 - arielb1:no-unneeded-unwind, r=eddyb

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rustc_mir: don't build unused unwind cleanup blocks

When building a scope exit, don't build unwind cleanup blocks unless they will actually be used by the unwind path of a drop - the unused blocks are removed by SimplifyCfg, but they can cause a significant performance slowdown before they are removed. That fixes #43511.

Also a few other small MIR cleanups & optimizations.

r? @eddyb
This commit is contained in:
bors 2017-08-01 22:43:15 +00:00
commit 640cfc852a
13 changed files with 210 additions and 178 deletions
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13
src/librustc/mir/visit.rs
View File

@ -14,7 +14,6 @@ use ty::subst::Substs;
use ty::{ClosureSubsts, Region, Ty};
use mir::*;
use rustc_const_math::ConstUsize;
use rustc_data_structures::indexed_vec::Idx;
use syntax_pos::Span;
// # The MIR Visitor
@ -260,9 +259,15 @@ macro_rules! make_mir_visitor {
fn super_mir(&mut self,
mir: & $($mutability)* Mir<'tcx>) {
for index in 0..mir.basic_blocks().len() {
let block = BasicBlock::new(index);
self.visit_basic_block_data(block, &$($mutability)* mir[block]);
// for best performance, we want to use an iterator rather
// than a for-loop, to avoid calling Mir::invalidate for
// each basic block.
macro_rules! basic_blocks {
(mut) => (mir.basic_blocks_mut().iter_enumerated_mut());
() => (mir.basic_blocks().iter_enumerated());
};
for (bb, data) in basic_blocks!($($mutability)*) {
self.visit_basic_block_data(bb, data);
}
for scope in &$($mutability)* mir.visibility_scopes {

2
src/librustc_mir/build/block.rs
View File

@ -86,7 +86,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
let tcx = this.hir.tcx();
// Enter the remainder scope, i.e. the bindings' destruction scope.
this.push_scope(remainder_scope);
this.push_scope((remainder_scope, source_info));
let_extent_stack.push(remainder_scope);
// Declare the bindings, which may create a visibility scope.

2
src/librustc_mir/build/expr/into.rs
View File

@ -237,7 +237,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
.collect();
let success = this.cfg.start_new_block();
let cleanup = this.diverge_cleanup(expr_span);
let cleanup = this.diverge_cleanup();
this.cfg.terminate(block, source_info, TerminatorKind::Call {
func: fun,
args: args,

2
src/librustc_mir/build/matches/test.rs
View File

@ -306,7 +306,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
let bool_ty = self.hir.bool_ty();
let eq_result = self.temp(bool_ty, test.span);
let eq_block = self.cfg.start_new_block();
let cleanup = self.diverge_cleanup(test.span);
let cleanup = self.diverge_cleanup();
self.cfg.terminate(block, source_info, TerminatorKind::Call {
func: Operand::Constant(box Constant {
span: test.span,

114
src/librustc_mir/build/scope.rs
View File

@ -107,6 +107,9 @@ pub struct Scope<'tcx> {
/// the extent of this scope within source code.
extent: CodeExtent,
/// the span of that extent
extent_span: Span,
/// Whether there's anything to do for the cleanup path, that is,
/// when unwinding through this scope. This includes destructors,
/// but not StorageDead statements, which don't get emitted at all
@ -116,7 +119,7 @@ pub struct Scope<'tcx> {
/// * pollutting the cleanup MIR with StorageDead creates
/// landing pads even though there's no actual destructors
/// * freeing up stack space has no effect during unwinding
pub(super) needs_cleanup: bool,
needs_cleanup: bool,
/// set of lvalues to drop when exiting this scope. This starts
/// out empty but grows as variables are declared during the
@ -197,6 +200,15 @@ pub struct BreakableScope<'tcx> {
pub break_destination: Lvalue<'tcx>,
}
impl DropKind {
fn may_panic(&self) -> bool {
match *self {
DropKind::Value { .. } => true,
DropKind::Storage => false
}
}
}
impl<'tcx> Scope<'tcx> {
/// Invalidate all the cached blocks in the scope.
///
@ -282,7 +294,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
where F: FnOnce(&mut Builder<'a, 'gcx, 'tcx>) -> BlockAnd<R>
{
debug!("in_opt_scope(opt_extent={:?}, block={:?})", opt_extent, block);
if let Some(extent) = opt_extent { self.push_scope(extent.0); }
if let Some(extent) = opt_extent { self.push_scope(extent); }
let rv = unpack!(block = f(self));
if let Some(extent) = opt_extent {
unpack!(block = self.pop_scope(extent, block));
@ -301,7 +313,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
where F: FnOnce(&mut Builder<'a, 'gcx, 'tcx>) -> BlockAnd<R>
{
debug!("in_scope(extent={:?}, block={:?})", extent, block);
self.push_scope(extent.0);
self.push_scope(extent);
let rv = unpack!(block = f(self));
unpack!(block = self.pop_scope(extent, block));
debug!("in_scope: exiting extent={:?} block={:?}", extent, block);
@ -312,12 +324,13 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
/// scope and call `pop_scope` afterwards. Note that these two
/// calls must be paired; using `in_scope` as a convenience
/// wrapper maybe preferable.
pub fn push_scope(&mut self, extent: CodeExtent) {
pub fn push_scope(&mut self, extent: (CodeExtent, SourceInfo)) {
debug!("push_scope({:?})", extent);
let vis_scope = self.visibility_scope;
self.scopes.push(Scope {
visibility_scope: vis_scope,
extent: extent,
extent: extent.0,
extent_span: extent.1.span,
needs_cleanup: false,
drops: vec![],
free: None,
@ -333,9 +346,13 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
mut block: BasicBlock)
-> BlockAnd<()> {
debug!("pop_scope({:?}, {:?})", extent, block);
// We need to have `cached_block`s available for all the drops, so we call diverge_cleanup
// to make sure all the `cached_block`s are filled in.
self.diverge_cleanup(extent.1.span);
// If we are emitting a `drop` statement, we need to have the cached
// diverge cleanup pads ready in case that drop panics.
let may_panic =
self.scopes.last().unwrap().drops.iter().any(|s| s.kind.may_panic());
if may_panic {
self.diverge_cleanup();
}
let scope = self.scopes.pop().unwrap();
assert_eq!(scope.extent, extent.0);
unpack!(block = build_scope_drops(&mut self.cfg,
@ -366,6 +383,15 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
let len = self.scopes.len();
assert!(scope_count < len, "should not use `exit_scope` to pop ALL scopes");
let tmp = self.get_unit_temp();
// If we are emitting a `drop` statement, we need to have the cached
// diverge cleanup pads ready in case that drop panics.
let may_panic = self.scopes[(len - scope_count)..].iter()
.any(|s| s.drops.iter().any(|s| s.kind.may_panic()));
if may_panic {
self.diverge_cleanup();
}
{
let mut rest = &mut self.scopes[(len - scope_count)..];
while let Some((scope, rest_)) = {rest}.split_last_mut() {
@ -618,7 +644,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
/// This path terminates in Resume. Returns the start of the path.
/// See module comment for more details. None indicates there’s no
/// cleanup to do at this point.
pub fn diverge_cleanup(&mut self, span: Span) -> Option<BasicBlock> {
pub fn diverge_cleanup(&mut self) -> Option<BasicBlock> {
if !self.scopes.iter().any(|scope| scope.needs_cleanup) {
return None;
}
@ -652,7 +678,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
};
for scope in scopes.iter_mut() {
target = build_diverge_scope(hir.tcx(), cfg, &unit_temp, span, scope, target);
target = build_diverge_scope(
hir.tcx(), cfg, &unit_temp, scope.extent_span, scope, target);
}
Some(target)
}
@ -668,7 +695,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
}
let source_info = self.source_info(span);
let next_target = self.cfg.start_new_block();
let diverge_target = self.diverge_cleanup(span);
let diverge_target = self.diverge_cleanup();
self.cfg.terminate(block, source_info,
TerminatorKind::Drop {
location: location,
@ -686,7 +713,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
value: Operand<'tcx>) -> BlockAnd<()> {
let source_info = self.source_info(span);
let next_target = self.cfg.start_new_block();
let diverge_target = self.diverge_cleanup(span);
let diverge_target = self.diverge_cleanup();
self.cfg.terminate(block, source_info,
TerminatorKind::DropAndReplace {
location: location,
@ -709,7 +736,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
let source_info = self.source_info(span);
let success_block = self.cfg.start_new_block();
let cleanup = self.diverge_cleanup(span);
let cleanup = self.diverge_cleanup();
self.cfg.terminate(block, source_info,
TerminatorKind::Assert {
@ -731,45 +758,48 @@ fn build_scope_drops<'tcx>(cfg: &mut CFG<'tcx>,
mut block: BasicBlock,
arg_count: usize)
-> BlockAnd<()> {
debug!("build_scope_drops({:?} -> {:?})", block, scope);
let mut iter = scope.drops.iter().rev().peekable();
while let Some(drop_data) = iter.next() {
let source_info = scope.source_info(drop_data.span);
if let DropKind::Value { .. } = drop_data.kind {
// Try to find the next block with its cached block
// for us to diverge into in case the drop panics.
let on_diverge = iter.peek().iter().filter_map(|dd| {
match dd.kind {
DropKind::Value { cached_block } => cached_block,
DropKind::Storage => None
}
}).next();
// If there’s no `cached_block`s within current scope,
// we must look for one in the enclosing scope.
let on_diverge = on_diverge.or_else(||{
earlier_scopes.iter().rev().flat_map(|s| s.cached_block()).next()
});
let next = cfg.start_new_block();
cfg.terminate(block, source_info, TerminatorKind::Drop {
location: drop_data.location.clone(),
target: next,
unwind: on_diverge
});
block = next;
}
match drop_data.kind {
DropKind::Value { .. } |
DropKind::Storage => {
// Only temps and vars need their storage dead.
match drop_data.location {
Lvalue::Local(index) if index.index() > arg_count => {}
_ => continue
}
DropKind::Value { .. } => {
// Try to find the next block with its cached block
// for us to diverge into in case the drop panics.
let on_diverge = iter.peek().iter().filter_map(|dd| {
match dd.kind {
DropKind::Value { cached_block: None } =>
span_bug!(drop_data.span, "cached block not present?"),
DropKind::Value { cached_block } => cached_block,
DropKind::Storage => None
}
}).next();
// If there’s no `cached_block`s within current scope,
// we must look for one in the enclosing scope.
let on_diverge = on_diverge.or_else(|| {
earlier_scopes.iter().rev().flat_map(|s| s.cached_block()).next()
});
let next = cfg.start_new_block();
cfg.terminate(block, source_info, TerminatorKind::Drop {
location: drop_data.location.clone(),
target: next,
unwind: on_diverge
});
block = next;
}
DropKind::Storage => {}
}
// Drop the storage for both value and storage drops.
// Only temps and vars need their storage dead.
match drop_data.location {
Lvalue::Local(index) if index.index() > arg_count => {
cfg.push(block, Statement {
source_info: source_info,
kind: StatementKind::StorageDead(drop_data.location.clone())
});
}
_ => continue
}
}
block.unit()

4
src/librustc_mir/transform/simplify.rs
View File

@ -105,6 +105,8 @@ impl<'a, 'tcx: 'a> CfgSimplifier<'a, 'tcx> {
}
pub fn simplify(mut self) {
self.strip_nops();
loop {
let mut changed = false;
@ -141,8 +143,6 @@ impl<'a, 'tcx: 'a> CfgSimplifier<'a, 'tcx> {
if !changed { break }
}
self.strip_nops()
}
// Collapse a goto chain starting from `start`

32
src/test/mir-opt/basic_assignment.rs
View File

@ -47,42 +47,36 @@ fn main() {
// StorageDead(_3);
// StorageLive(_4);
// _4 = std::option::Option<std::boxed::Box<u32>>::None;
// StorageLive(_5);
// StorageLive(_6);
// StorageLive(_7);
// _7 = _4;
// replace(_6 <- _7) -> [return: bb6, unwind: bb7];
// _6 = _4;
// replace(_5 <- _6) -> [return: bb1, unwind: bb5];
// }
// bb1: {
// resume;
// drop(_6) -> [return: bb6, unwind: bb4];
// }
// bb2: {
// drop(_4) -> bb1;
// resume;
// }
// bb3: {
// goto -> bb2;
// drop(_4) -> bb2;
// }
// bb4: {
// drop(_6) -> bb3;
// drop(_5) -> bb3;
// }
// bb5: {
// goto -> bb4;
// drop(_6) -> bb4;
// }
// bb6: {
// drop(_7) -> [return: bb8, unwind: bb4];
// StorageDead(_6);
// _0 = ();
// drop(_5) -> [return: bb7, unwind: bb3];
// }
// bb7: {
// drop(_7) -> bb5;
// StorageDead(_5);
// drop(_4) -> bb8;
// }
// bb8: {
// StorageDead(_7);
// _0 = ();
// drop(_6) -> [return: bb9, unwind: bb2];
// }
// bb9: {
// StorageDead(_6);
// drop(_4) -> bb10;
// }
// bb10: {
// StorageDead(_4);
// StorageDead(_2);
// StorageDead(_1);

38
src/test/mir-opt/end_region_4.rs
View File

@ -32,41 +32,41 @@ fn foo(i: i32) {
// START rustc.node4.SimplifyCfg-qualify-consts.after.mir
// let mut _0: ();
// let _1: D;
// let _3: i32;
// let _4: &'6_2rce i32;
// let _2: i32;
// let _3: &'6_2rce i32;
// let _7: &'6_4rce i32;
// let mut _5: ();
// let mut _6: i32;
//
// let mut _4: ();
// let mut _5: i32;
// let mut _6: ();
// bb0: {
// StorageLive(_1);
// _1 = D::{{constructor}}(const 0i32,);
// StorageLive(_2);
// _2 = const 0i32;
// StorageLive(_3);
// _3 = const 0i32;
// StorageLive(_4);
// _4 = &'6_2rce _3;
// StorageLive(_6);
// _6 = (*_4);
// _5 = const foo(_6) -> [return: bb2, unwind: bb3];
// _3 = &'6_2rce _2;
// StorageLive(_5);
// _5 = (*_3);
// _4 = const foo(_5) -> [return: bb1, unwind: bb3];
// }
// bb1: {
// resume;
// }
// bb2: {
// StorageDead(_6);
// StorageDead(_5);
// StorageLive(_7);
// _7 = &'6_4rce _3;
// _7 = &'6_4rce _2;
// _0 = ();
// StorageDead(_7);
// EndRegion('6_4rce);
// StorageDead(_4);
// EndRegion('6_2rce);
// StorageDead(_3);
// EndRegion('6_2rce);
// StorageDead(_2);
// drop(_1) -> bb4;
// }
// bb2: {
// resume;
// }
// bb3: {
// EndRegion('6_2rce);
// drop(_1) -> bb1;
// drop(_1) -> bb2;
// }
// bb4: {
// StorageDead(_1);

27
src/test/mir-opt/end_region_5.rs
View File

@ -31,32 +31,31 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// let mut _0: ();
// let _1: D;
// let mut _2: ();
// let mut _3: ();
// let mut _4: [closure@NodeId(18) d: &'19mce D];
// let mut _5: &'19mce D;
//
// let mut _3: [closure@NodeId(18) d:&'19mce D];
// let mut _4: &'19mce D;
// let mut _5: ();
// bb0: {
// StorageLive(_1);
// _1 = D::{{constructor}}(const 0i32,);
// StorageLive(_3);
// StorageLive(_4);
// StorageLive(_5);
// _5 = &'19mce _1;
// _4 = [closure@NodeId(18)] { d: _5 };
// StorageDead(_5);
// _3 = const foo(_4) -> [return: bb2, unwind: bb3];
// _4 = &'19mce _1;
// _3 = [closure@NodeId(18)] { d: _4 };
// StorageDead(_4);
// _2 = const foo(_3) -> [return: bb1, unwind: bb3];
// }
// bb1: {
// resume;
// }
// bb2: {
// StorageDead(_4);
// StorageDead(_3);
// EndRegion('19mce);
// _0 = ();
// drop(_1) -> bb4;
// }
// bb2: {
// resume;
// }
// bb3: {
// EndRegion('19mce);
// drop(_1) -> bb1;
// drop(_1) -> bb2;
// }
// bb4: {
// StorageDead(_1);

28
src/test/mir-opt/end_region_6.rs
View File

@ -27,35 +27,35 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// END RUST SOURCE
// START rustc.node4.SimplifyCfg-qualify-consts.after.mir
// fn main() -> () {
// let mut _0: ();
// let _1: D;
// let mut _2: ();
// let mut _3: ();
// let mut _4: [closure@NodeId(22) d:&'23mce D];
// let mut _5: &'23mce D;
//
// let mut _3: [closure@NodeId(22) d:&'23mce D];
// let mut _4: &'23mce D;
// let mut _5: ();
// bb0: {
// StorageLive(_1);
// _1 = D::{{constructor}}(const 0i32,);
// StorageLive(_3);
// StorageLive(_4);
// StorageLive(_5);
// _5 = &'23mce _1;
// _4 = [closure@NodeId(22)] { d: _5 };
// StorageDead(_5);
// _3 = const foo(_4) -> [return: bb2, unwind: bb3];
// _4 = &'23mce _1;
// _3 = [closure@NodeId(22)] { d: _4 };
// StorageDead(_4);
// _2 = const foo(_3) -> [return: bb1, unwind: bb3];
// }
// bb1: {
// resume;
// }
// bb2: {
// StorageDead(_4);
// StorageDead(_3);
// EndRegion('23mce);
// _0 = ();
// drop(_1) -> bb4;
// }
// bb2: {
// resume;
// }
// bb3: {
// EndRegion('23mce);
// drop(_1) -> bb1;
// drop(_1) -> bb2;
// }
// bb4: {
// StorageDead(_1);

36
src/test/mir-opt/end_region_7.rs
View File

@ -31,18 +31,18 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// let mut _0: ();
// let _1: D;
// let mut _2: ();
// let mut _3: ();
// let mut _4: [closure@NodeId(22) d:D];
// let mut _5: D;
// let mut _3: [closure@NodeId(22) d:D];
// let mut _4: D;
// let mut _5: ();
//
// bb0: {
// StorageLive(_1);
// _1 = D::{{constructor}}(const 0i32,);
// StorageLive(_3);
// StorageLive(_4);
// StorageLive(_5);
// _5 = _1;
// _4 = [closure@NodeId(22)] { d: _5 };
// drop(_5) -> [return: bb4, unwind: bb3];
// _4 = _1;
// _3 = [closure@NodeId(22)] { d: _4 };
// drop(_4) -> [return: bb4, unwind: bb3];
// }
// bb1: {
// resume;
@ -51,17 +51,17 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// drop(_1) -> bb1;
// }
// bb3: {
// drop(_4) -> bb2;
// drop(_3) -> bb2;
// }
// bb4: {
// StorageDead(_5);
// _3 = const foo(_4) -> [return: bb5, unwind: bb3];
// StorageDead(_4);
// _2 = const foo(_3) -> [return: bb5, unwind: bb3];
// }
// bb5: {
// drop(_4) -> [return: bb6, unwind: bb2];
// drop(_3) -> [return: bb6, unwind: bb2];
// }
// bb6: {
// StorageDead(_4);
// StorageDead(_3);
// _0 = ();
// drop(_1) -> bb7;
// }
@ -76,16 +76,16 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// fn main::{{closure}}(_1: [closure@NodeId(22) d:D]) -> i32 {
// let mut _0: i32;
// let _2: &'14_0rce D;
// let mut _3: ();
// let mut _4: i32;
// let mut _3: i32;
// let mut _4: ();
//
// bb0: {
// StorageLive(_2);
// _2 = &'14_0rce (_1.0: D);
// StorageLive(_4);
// _4 = ((*_2).0: i32);
// _0 = _4;
// StorageDead(_4);
// StorageLive(_3);
// _3 = ((*_2).0: i32);
// _0 = _3;
// StorageDead(_3);
// StorageDead(_2);
// EndRegion('14_0rce);
// drop(_1) -> bb1;

75
src/test/mir-opt/end_region_8.rs
View File

@ -29,44 +29,43 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// END RUST SOURCE
// START rustc.node4.SimplifyCfg-qualify-consts.after.mir
// fn main() -> () {
// let mut _0: ();
// let _1: D;
// let _3: &'6_1rce D;
// let mut _2: ();
// let mut _4: ();
// let mut _5: [closure@NodeId(22) r:&'6_1rce D];
// let mut _6: &'6_1rce D;
//
// bb0: {
// StorageLive(_1);
// _1 = D::{{constructor}}(const 0i32,);
// StorageLive(_3);
// _3 = &'6_1rce _1;
// StorageLive(_5);
// StorageLive(_6);
// _6 = _3;
// _5 = [closure@NodeId(22)] { r: _6 };
// StorageDead(_6);
// _4 = const foo(_5) -> [return: bb2, unwind: bb3];
// }
// bb1: {
// resume;
// }
// bb2: {
// StorageDead(_5);
// _0 = ();
// StorageDead(_3);
// EndRegion('6_1rce);
// drop(_1) -> bb4;
// }
// bb3: {
// EndRegion('6_1rce);
// drop(_1) -> bb1;
// }
// bb4: {
// StorageDead(_1);
// return;
// }
// let mut _0: ();
// let _1: D;
// let _2: &'6_1rce D;
// let mut _3: ();
// let mut _4: [closure@NodeId(22) r:&'6_1rce D];
// let mut _5: &'6_1rce D;
// let mut _6: ();
// bb0: {
// StorageLive(_1);
// _1 = D::{{constructor}}(const 0i32,);
// StorageLive(_2);
// _2 = &'6_1rce _1;
// StorageLive(_4);
// StorageLive(_5);
// _5 = _2;
// _4 = [closure@NodeId(22)] { r: _5 };
// StorageDead(_5);
// _3 = const foo(_4) -> [return: bb1, unwind: bb3];
// }
// bb1: {
// StorageDead(_4);
// _0 = ();
// StorageDead(_2);
// EndRegion('6_1rce);
// drop(_1) -> bb4;
// }
// bb2: {
// resume;
// }
// bb3: {
// EndRegion('6_1rce);
// drop(_1) -> bb2;
// }
// bb4: {
// StorageDead(_1);
// return;
// }
// }
// END rustc.node4.SimplifyCfg-qualify-consts.after.mir

15
src/test/mir-opt/issue-41110.rs
View File

@ -34,18 +34,23 @@ impl S {
// END RUST SOURCE
// START rustc.node4.ElaborateDrops.after.mir
// let mut _0: ();
// let _1: ();
// let mut _2: S;
// let mut _3: ();
// let mut _3: S;
// let mut _4: S;
// let mut _5: S;
// let mut _5: ();
// let mut _6: bool;
//
// bb0: {
// END rustc.node4.ElaborateDrops.after.mir
// START rustc.node13.ElaborateDrops.after.mir
// let mut _2: ();
// let mut _4: ();
// let mut _5: S;
// let mut _0: ();
// let _1: S;
// let mut _2: S;
// let mut _3: ();
// let mut _4: S;
// let mut _5: ();
// let mut _6: S;
// let mut _7: bool;
//