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tmiaskotmiasko
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Use let else to reduce indentation
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‎compiler/rustc_mir_transform/src/inline.rs

+123-124
Original file line numberDiff line numberDiff line change
@@ -541,142 +541,141 @@ impl<'tcx> Inliner<'tcx> {
541541
mut callee_body: Body<'tcx>,
542542
) {
543543
let terminator = caller_body[callsite.block].terminator.take().unwrap();
544-
match terminator.kind {
545-
TerminatorKind::Call { args, destination, unwind, .. } => {
546-
// If the call is something like `a[*i] = f(i)`, where
547-
// `i : &mut usize`, then just duplicating the `a[*i]`
548-
// Place could result in two different locations if `f`
549-
// writes to `i`. To prevent this we need to create a temporary
550-
// borrow of the place and pass the destination as `*temp` instead.
551-
fn dest_needs_borrow(place: Place<'_>) -> bool {
552-
for elem in place.projection.iter() {
553-
match elem {
554-
ProjectionElem::Deref | ProjectionElem::Index(_) => return true,
555-
_ => {}
556-
}
557-
}
544+
let TerminatorKind::Call { args, destination, unwind, .. } = terminator.kind else {
545+
bug!("unexpected terminator kind {:?}", terminator.kind);
546+
};
558547

559-
false
548+
// If the call is something like `a[*i] = f(i)`, where
549+
// `i : &mut usize`, then just duplicating the `a[*i]`
550+
// Place could result in two different locations if `f`
551+
// writes to `i`. To prevent this we need to create a temporary
552+
// borrow of the place and pass the destination as `*temp` instead.
553+
fn dest_needs_borrow(place: Place<'_>) -> bool {
554+
for elem in place.projection.iter() {
555+
match elem {
556+
ProjectionElem::Deref | ProjectionElem::Index(_) => return true,
557+
_ => {}
560558
}
559+
}
561560

562-
let dest = if dest_needs_borrow(destination) {
563-
trace!("creating temp for return destination");
564-
let dest = Rvalue::Ref(
565-
self.tcx.lifetimes.re_erased,
566-
BorrowKind::Mut { kind: MutBorrowKind::Default },
567-
destination,
568-
);
569-
let dest_ty = dest.ty(caller_body, self.tcx);
570-
let temp = Place::from(self.new_call_temp(caller_body, &callsite, dest_ty));
571-
caller_body[callsite.block].statements.push(Statement {
572-
source_info: callsite.source_info,
573-
kind: StatementKind::Assign(Box::new((temp, dest))),
574-
});
575-
self.tcx.mk_place_deref(temp)
576-
} else {
577-
destination
578-
};
561+
false
562+
}
579563

580-
// Always create a local to hold the destination, as `RETURN_PLACE` may appear
581-
// where a full `Place` is not allowed.
582-
let (remap_destination, destination_local) = if let Some(d) = dest.as_local() {
583-
(false, d)
584-
} else {
585-
(
586-
true,
587-
self.new_call_temp(
588-
caller_body,
589-
&callsite,
590-
destination.ty(caller_body, self.tcx).ty,
591-
),
592-
)
593-
};
564+
let dest = if dest_needs_borrow(destination) {
565+
trace!("creating temp for return destination");
566+
let dest = Rvalue::Ref(
567+
self.tcx.lifetimes.re_erased,
568+
BorrowKind::Mut { kind: MutBorrowKind::Default },
569+
destination,
570+
);
571+
let dest_ty = dest.ty(caller_body, self.tcx);
572+
let temp = Place::from(self.new_call_temp(caller_body, &callsite, dest_ty));
573+
caller_body[callsite.block].statements.push(Statement {
574+
source_info: callsite.source_info,
575+
kind: StatementKind::Assign(Box::new((temp, dest))),
576+
});
577+
self.tcx.mk_place_deref(temp)
578+
} else {
579+
destination
580+
};
594581

595-
// Copy the arguments if needed.
596-
let args: Vec<_> = self.make_call_args(args, &callsite, caller_body, &callee_body);
597-
598-
let mut integrator = Integrator {
599-
args: &args,
600-
new_locals: Local::new(caller_body.local_decls.len())..,
601-
new_scopes: SourceScope::new(caller_body.source_scopes.len())..,
602-
new_blocks: BasicBlock::new(caller_body.basic_blocks.len())..,
603-
destination: destination_local,
604-
callsite_scope: caller_body.source_scopes[callsite.source_info.scope].clone(),
605-
callsite,
606-
cleanup_block: unwind,
607-
in_cleanup_block: false,
608-
tcx: self.tcx,
609-
always_live_locals: BitSet::new_filled(callee_body.local_decls.len()),
610-
};
582+
// Always create a local to hold the destination, as `RETURN_PLACE` may appear
583+
// where a full `Place` is not allowed.
584+
let (remap_destination, destination_local) = if let Some(d) = dest.as_local() {
585+
(false, d)
586+
} else {
587+
(
588+
true,
589+
self.new_call_temp(
590+
caller_body,
591+
&callsite,
592+
destination.ty(caller_body, self.tcx).ty,
593+
),
594+
)
595+
};
611596

612-
// Map all `Local`s, `SourceScope`s and `BasicBlock`s to new ones
613-
// (or existing ones, in a few special cases) in the caller.
614-
integrator.visit_body(&mut callee_body);
615-
616-
// If there are any locals without storage markers, give them storage only for the
617-
// duration of the call.
618-
for local in callee_body.vars_and_temps_iter() {
619-
if integrator.always_live_locals.contains(local) {
620-
let new_local = integrator.map_local(local);
621-
caller_body[callsite.block].statements.push(Statement {
622-
source_info: callsite.source_info,
623-
kind: StatementKind::StorageLive(new_local),
624-
});
625-
}
626-
}
627-
if let Some(block) = callsite.target {
628-
// To avoid repeated O(n) insert, push any new statements to the end and rotate
629-
// the slice once.
630-
let mut n = 0;
631-
if remap_destination {
632-
caller_body[block].statements.push(Statement {
633-
source_info: callsite.source_info,
634-
kind: StatementKind::Assign(Box::new((
635-
dest,
636-
Rvalue::Use(Operand::Move(destination_local.into())),
637-
))),
638-
});
639-
n += 1;
640-
}
641-
for local in callee_body.vars_and_temps_iter().rev() {
642-
if integrator.always_live_locals.contains(local) {
643-
let new_local = integrator.map_local(local);
644-
caller_body[block].statements.push(Statement {
645-
source_info: callsite.source_info,
646-
kind: StatementKind::StorageDead(new_local),
647-
});
648-
n += 1;
649-
}
650-
}
651-
caller_body[block].statements.rotate_right(n);
652-
}
597+
// Copy the arguments if needed.
598+
let args: Vec<_> = self.make_call_args(args, &callsite, caller_body, &callee_body);
599+
600+
let mut integrator = Integrator {
601+
args: &args,
602+
new_locals: Local::new(caller_body.local_decls.len())..,
603+
new_scopes: SourceScope::new(caller_body.source_scopes.len())..,
604+
new_blocks: BasicBlock::new(caller_body.basic_blocks.len())..,
605+
destination: destination_local,
606+
callsite_scope: caller_body.source_scopes[callsite.source_info.scope].clone(),
607+
callsite,
608+
cleanup_block: unwind,
609+
in_cleanup_block: false,
610+
tcx: self.tcx,
611+
always_live_locals: BitSet::new_filled(callee_body.local_decls.len()),
612+
};
653613

654-
// Insert all of the (mapped) parts of the callee body into the caller.
655-
caller_body.local_decls.extend(callee_body.drain_vars_and_temps());
656-
caller_body.source_scopes.extend(&mut callee_body.source_scopes.drain(..));
657-
caller_body.var_debug_info.append(&mut callee_body.var_debug_info);
658-
caller_body.basic_blocks_mut().extend(callee_body.basic_blocks_mut().drain(..));
614+
// Map all `Local`s, `SourceScope`s and `BasicBlock`s to new ones
615+
// (or existing ones, in a few special cases) in the caller.
616+
integrator.visit_body(&mut callee_body);
659617

660-
caller_body[callsite.block].terminator = Some(Terminator {
618+
// If there are any locals without storage markers, give them storage only for the
619+
// duration of the call.
620+
for local in callee_body.vars_and_temps_iter() {
621+
if integrator.always_live_locals.contains(local) {
622+
let new_local = integrator.map_local(local);
623+
caller_body[callsite.block].statements.push(Statement {
661624
source_info: callsite.source_info,
662-
kind: TerminatorKind::Goto { target: integrator.map_block(START_BLOCK) },
625+
kind: StatementKind::StorageLive(new_local),
663626
});
664-
665-
// Copy only unevaluated constants from the callee_body into the caller_body.
666-
// Although we are only pushing `ConstKind::Unevaluated` consts to
667-
// `required_consts`, here we may not only have `ConstKind::Unevaluated`
668-
// because we are calling `instantiate_and_normalize_erasing_regions`.
669-
caller_body.required_consts.extend(
670-
callee_body.required_consts.iter().copied().filter(|&ct| match ct.const_ {
671-
Const::Ty(_) => {
672-
bug!("should never encounter ty::UnevaluatedConst in `required_consts`")
673-
}
674-
Const::Val(..) | Const::Unevaluated(..) => true,
675-
}),
676-
);
677627
}
678-
kind => bug!("unexpected terminator kind {:?}", kind),
679628
}
629+
if let Some(block) = callsite.target {
630+
// To avoid repeated O(n) insert, push any new statements to the end and rotate
631+
// the slice once.
632+
let mut n = 0;
633+
if remap_destination {
634+
caller_body[block].statements.push(Statement {
635+
source_info: callsite.source_info,
636+
kind: StatementKind::Assign(Box::new((
637+
dest,
638+
Rvalue::Use(Operand::Move(destination_local.into())),
639+
))),
640+
});
641+
n += 1;
642+
}
643+
for local in callee_body.vars_and_temps_iter().rev() {
644+
if integrator.always_live_locals.contains(local) {
645+
let new_local = integrator.map_local(local);
646+
caller_body[block].statements.push(Statement {
647+
source_info: callsite.source_info,
648+
kind: StatementKind::StorageDead(new_local),
649+
});
650+
n += 1;
651+
}
652+
}
653+
caller_body[block].statements.rotate_right(n);
654+
}
655+
656+
// Insert all of the (mapped) parts of the callee body into the caller.
657+
caller_body.local_decls.extend(callee_body.drain_vars_and_temps());
658+
caller_body.source_scopes.extend(&mut callee_body.source_scopes.drain(..));
659+
caller_body.var_debug_info.append(&mut callee_body.var_debug_info);
660+
caller_body.basic_blocks_mut().extend(callee_body.basic_blocks_mut().drain(..));
661+
662+
caller_body[callsite.block].terminator = Some(Terminator {
663+
source_info: callsite.source_info,
664+
kind: TerminatorKind::Goto { target: integrator.map_block(START_BLOCK) },
665+
});
666+
667+
// Copy only unevaluated constants from the callee_body into the caller_body.
668+
// Although we are only pushing `ConstKind::Unevaluated` consts to
669+
// `required_consts`, here we may not only have `ConstKind::Unevaluated`
670+
// because we are calling `instantiate_and_normalize_erasing_regions`.
671+
caller_body.required_consts.extend(callee_body.required_consts.iter().copied().filter(
672+
|&ct| match ct.const_ {
673+
Const::Ty(_) => {
674+
bug!("should never encounter ty::UnevaluatedConst in `required_consts`")
675+
}
676+
Const::Val(..) | Const::Unevaluated(..) => true,
677+
},
678+
));
680679
}
681680

682681
fn make_call_args(

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