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Cleanup the InstSimplify MIR transformation
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‎compiler/rustc_mir_transform/src/instsimplify.rs‎

Lines changed: 79 additions & 91 deletions
Original file line numberDiff line numberDiff line change
@@ -39,26 +39,26 @@ impl<'tcx> crate::MirPass<'tcx> for InstSimplify {
3939
attr::contains_name(tcx.hir_krate_attrs(), sym::rustc_preserve_ub_checks);
4040
for block in body.basic_blocks.as_mut() {
4141
for statement in block.statements.iter_mut() {
42-
match statement.kind {
43-
StatementKind::Assign(box (_place, ref mut rvalue)) => {
44-
if !preserve_ub_checks {
45-
ctx.simplify_ub_check(rvalue);
46-
}
47-
ctx.simplify_bool_cmp(rvalue);
48-
ctx.simplify_ref_deref(rvalue);
49-
ctx.simplify_ptr_aggregate(rvalue);
50-
ctx.simplify_cast(rvalue);
51-
ctx.simplify_repeated_aggregate(rvalue);
52-
ctx.simplify_repeat_once(rvalue);
53-
}
54-
_ => {}
42+
let StatementKind::Assign(box (.., rvalue)) = &mut statement.kind else {
43+
continue;
44+
};
45+
46+
if !preserve_ub_checks {
47+
ctx.simplify_ub_check(rvalue);
5548
}
49+
ctx.simplify_bool_cmp(rvalue);
50+
ctx.simplify_ref_deref(rvalue);
51+
ctx.simplify_ptr_aggregate(rvalue);
52+
ctx.simplify_cast(rvalue);
53+
ctx.simplify_repeated_aggregate(rvalue);
54+
ctx.simplify_repeat_once(rvalue);
5655
}
5756

58-
ctx.simplify_primitive_clone(block.terminator.as_mut().unwrap(), &mut block.statements);
59-
ctx.simplify_intrinsic_assert(block.terminator.as_mut().unwrap());
60-
ctx.simplify_nounwind_call(block.terminator.as_mut().unwrap());
61-
simplify_duplicate_switch_targets(block.terminator.as_mut().unwrap());
57+
let terminator = block.terminator.as_mut().unwrap();
58+
ctx.simplify_primitive_clone(terminator, &mut block.statements);
59+
ctx.simplify_intrinsic_assert(terminator);
60+
ctx.simplify_nounwind_call(terminator);
61+
simplify_duplicate_switch_targets(terminator);
6262
}
6363
}
6464

@@ -105,43 +105,34 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
105105

106106
/// Transform boolean comparisons into logical operations.
107107
fn simplify_bool_cmp(&self, rvalue: &mut Rvalue<'tcx>) {
108-
match rvalue {
109-
Rvalue::BinaryOp(op @ (BinOp::Eq | BinOp::Ne), box (a, b)) => {
110-
let new = match (op, self.try_eval_bool(a), self.try_eval_bool(b)) {
111-
// Transform "Eq(a, true)" ==> "a"
112-
(BinOp::Eq, _, Some(true)) => Some(Rvalue::Use(a.clone())),
113-
114-
// Transform "Ne(a, false)" ==> "a"
115-
(BinOp::Ne, _, Some(false)) => Some(Rvalue::Use(a.clone())),
108+
let Rvalue::BinaryOp(op @ (BinOp::Eq | BinOp::Ne), box (a, b)) = &*rvalue else { return };
109+
*rvalue = match (op, self.try_eval_bool(a), self.try_eval_bool(b)) {
110+
// Transform "Eq(a, true)" ==> "a"
111+
(BinOp::Eq, _, Some(true)) => Rvalue::Use(a.clone()),
116112

117-
// Transform "Eq(true, b)" ==> "b"
118-
(BinOp::Eq, Some(true), _) => Some(Rvalue::Use(b.clone())),
113+
// Transform "Ne(a, false)" ==> "a"
114+
(BinOp::Ne, _, Some(false)) => Rvalue::Use(a.clone()),
119115

120-
// Transform "Ne(false, b)" ==> "b"
121-
(BinOp::Ne, Some(false), _) => Some(Rvalue::Use(b.clone())),
116+
// Transform "Eq(true, b)" ==> "b"
117+
(BinOp::Eq, Some(true), _) => Rvalue::Use(b.clone()),
122118

123-
// Transform "Eq(false, b)" ==> "Not(b)"
124-
(BinOp::Eq, Some(false), _) => Some(Rvalue::UnaryOp(UnOp::Not, b.clone())),
119+
// Transform "Ne(false, b)" ==> "b"
120+
(BinOp::Ne, Some(false), _) => Rvalue::Use(b.clone()),
125121

126-
// Transform "Ne(true, b)" ==> "Not(b)"
127-
(BinOp::Ne, Some(true), _) => Some(Rvalue::UnaryOp(UnOp::Not, b.clone())),
122+
// Transform "Eq(false, b)" ==> "Not(b)"
123+
(BinOp::Eq, Some(false), _) => Rvalue::UnaryOp(UnOp::Not, b.clone()),
128124

129-
// Transform "Eq(a, false)" ==> "Not(a)"
130-
(BinOp::Eq, _, Some(false)) => Some(Rvalue::UnaryOp(UnOp::Not, a.clone())),
125+
// Transform "Ne(true, b)" ==> "Not(b)"
126+
(BinOp::Ne, Some(true), _) => Rvalue::UnaryOp(UnOp::Not, b.clone()),
131127

132-
// Transform "Ne(a, true)" ==> "Not(a)"
133-
(BinOp::Ne, _, Some(true)) => Some(Rvalue::UnaryOp(UnOp::Not, a.clone())),
134-
135-
_ => None,
136-
};
128+
// Transform "Eq(a, false)" ==> "Not(a)"
129+
(BinOp::Eq, _, Some(false)) => Rvalue::UnaryOp(UnOp::Not, a.clone()),
137130

138-
if let Some(new) = new {
139-
*rvalue = new;
140-
}
141-
}
131+
// Transform "Ne(a, true)" ==> "Not(a)"
132+
(BinOp::Ne, _, Some(true)) => Rvalue::UnaryOp(UnOp::Not, a.clone()),
142133

143-
_ => {}
144-
}
134+
_ => return,
135+
};
145136
}
146137

147138
fn try_eval_bool(&self, a: &Operand<'_>) -> Option<bool> {
@@ -151,64 +142,61 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
151142

152143
/// Transform `&(*a)` ==> `a`.
153144
fn simplify_ref_deref(&self, rvalue: &mut Rvalue<'tcx>) {
154-
if let Rvalue::Ref(_, _, place) | Rvalue::RawPtr(_, place) = rvalue {
155-
if let Some((base, ProjectionElem::Deref)) = place.as_ref().last_projection() {
156-
if rvalue.ty(self.local_decls, self.tcx) != base.ty(self.local_decls, self.tcx).ty {
157-
return;
158-
}
159-
160-
*rvalue = Rvalue::Use(Operand::Copy(Place {
161-
local: base.local,
162-
projection: self.tcx.mk_place_elems(base.projection),
163-
}));
145+
if let Rvalue::Ref(_, _, place) | Rvalue::RawPtr(_, place) = rvalue
146+
&& let Some((base, ProjectionElem::Deref)) = place.as_ref().last_projection()
147+
{
148+
if rvalue.ty(self.local_decls, self.tcx) != base.ty(self.local_decls, self.tcx).ty {
149+
return;
164150
}
151+
152+
*rvalue = Rvalue::Use(Operand::Copy(Place {
153+
local: base.local,
154+
projection: self.tcx.mk_place_elems(base.projection),
155+
}));
165156
}
166157
}
167158

168159
/// Transform `Aggregate(RawPtr, [p, ()])` ==> `Cast(PtrToPtr, p)`.
169160
fn simplify_ptr_aggregate(&self, rvalue: &mut Rvalue<'tcx>) {
170161
if let Rvalue::Aggregate(box AggregateKind::RawPtr(pointee_ty, mutability), fields) = rvalue
162+
&& let meta_ty = fields.raw[1].ty(self.local_decls, self.tcx)
163+
&& meta_ty.is_unit()
171164
{
172-
let meta_ty = fields.raw[1].ty(self.local_decls, self.tcx);
173-
if meta_ty.is_unit() {
174-
// The mutable borrows we're holding prevent printing `rvalue` here
175-
let mut fields = std::mem::take(fields);
176-
let _meta = fields.pop().unwrap();
177-
let data = fields.pop().unwrap();
178-
let ptr_ty = Ty::new_ptr(self.tcx, *pointee_ty, *mutability);
179-
*rvalue = Rvalue::Cast(CastKind::PtrToPtr, data, ptr_ty);
180-
}
165+
// The mutable borrows we're holding prevent printing `rvalue` here
166+
let mut fields = std::mem::take(fields);
167+
let _meta = fields.pop().unwrap();
168+
let data = fields.pop().unwrap();
169+
let ptr_ty = Ty::new_ptr(self.tcx, *pointee_ty, *mutability);
170+
*rvalue = Rvalue::Cast(CastKind::PtrToPtr, data, ptr_ty);
181171
}
182172
}
183173

184174
fn simplify_ub_check(&self, rvalue: &mut Rvalue<'tcx>) {
185-
if let Rvalue::NullaryOp(NullOp::UbChecks, _) = *rvalue {
186-
let const_ = Const::from_bool(self.tcx, self.tcx.sess.ub_checks());
187-
let constant = ConstOperand { span: DUMMY_SP, const_, user_ty: None };
188-
*rvalue = Rvalue::Use(Operand::Constant(Box::new(constant)));
189-
}
175+
let Rvalue::NullaryOp(NullOp::UbChecks, _) = *rvalue else { return };
176+
177+
let const_ = Const::from_bool(self.tcx, self.tcx.sess.ub_checks());
178+
let constant = ConstOperand { span: DUMMY_SP, const_, user_ty: None };
179+
*rvalue = Rvalue::Use(Operand::Constant(Box::new(constant)));
190180
}
191181

192182
fn simplify_cast(&self, rvalue: &mut Rvalue<'tcx>) {
193-
if let Rvalue::Cast(kind, operand, cast_ty) = rvalue {
194-
let operand_ty = operand.ty(self.local_decls, self.tcx);
195-
if operand_ty == *cast_ty {
196-
*rvalue = Rvalue::Use(operand.clone());
197-
} else if *kind == CastKind::Transmute {
198-
// Transmuting an integer to another integer is just a signedness cast
199-
if let (ty::Int(int), ty::Uint(uint)) | (ty::Uint(uint), ty::Int(int)) =
200-
(operand_ty.kind(), cast_ty.kind())
201-
&& int.bit_width() == uint.bit_width()
202-
{
203-
// The width check isn't strictly necessary, as different widths
204-
// are UB and thus we'd be allowed to turn it into a cast anyway.
205-
// But let's keep the UB around for codegen to exploit later.
206-
// (If `CastKind::Transmute` ever becomes *not* UB for mismatched sizes,
207-
// then the width check is necessary for big-endian correctness.)
208-
*kind = CastKind::IntToInt;
209-
return;
210-
}
211-
}
183+
let Rvalue::Cast(kind, operand, cast_ty) = rvalue else { return };
184+
185+
let operand_ty = operand.ty(self.local_decls, self.tcx);
186+
if operand_ty == *cast_ty {
187+
*rvalue = Rvalue::Use(operand.clone());
188+
} else if *kind == CastKind::Transmute
189+
// Transmuting an integer to another integer is just a signedness cast
190+
&& let (ty::Int(int), ty::Uint(uint)) | (ty::Uint(uint), ty::Int(int)) =
191+
(operand_ty.kind(), cast_ty.kind())
192+
&& int.bit_width() == uint.bit_width()
193+
{
194+
// The width check isn't strictly necessary, as different widths
195+
// are UB and thus we'd be allowed to turn it into a cast anyway.
196+
// But let's keep the UB around for codegen to exploit later.
197+
// (If `CastKind::Transmute` ever becomes *not* UB for mismatched sizes,
198+
// then the width check is necessary for big-endian correctness.)
199+
*kind = CastKind::IntToInt;
212200
}
213201
}
214202

@@ -277,7 +265,7 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
277265
}
278266

279267
fn simplify_nounwind_call(&self, terminator: &mut Terminator<'tcx>) {
280-
let TerminatorKind::Call { func, unwind, .. } = &mut terminator.kind else {
268+
let TerminatorKind::Call { ref func, ref mut unwind, .. } = terminator.kind else {
281269
return;
282270
};
283271

@@ -290,7 +278,7 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
290278
ty::FnDef(..) => body_ty.fn_sig(self.tcx).abi(),
291279
ty::Closure(..) => ExternAbi::RustCall,
292280
ty::Coroutine(..) => ExternAbi::Rust,
293-
_ => bug!("unexpected body ty: {:?}", body_ty),
281+
_ => bug!("unexpected body ty: {body_ty:?}"),
294282
};
295283

296284
if !layout::fn_can_unwind(self.tcx, Some(def_id), body_abi) {

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