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Some Promotion Refactoring #80458

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merged 4 commits into from
Dec 31, 2020
Merged

Some Promotion Refactoring #80458

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122e91c
promotion: factor some common code into validate_ref
RalfJung Dec 28, 2020
c177e68
merge two match'es for more exhaustiveness
RalfJung Dec 28, 2020
4a90a58
make more matches exhaustive
RalfJung Dec 28, 2020
51cec58
fix a comment
RalfJung Dec 29, 2020
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80 changes: 41 additions & 39 deletions compiler/rustc_mir/src/transform/promote_consts.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,7 @@ pub enum TempState {
impl TempState {
pub fn is_promotable(&self) -> bool {
debug!("is_promotable: self={:?}", self);
matches!(self, TempState::Defined { .. } )
matches!(self, TempState::Defined { .. })
}
}

Expand Down Expand Up @@ -329,7 +329,6 @@ impl<'tcx> Validator<'_, 'tcx> {
return Err(Unpromotable);
}


Ok(())
}
_ => bug!(),
Expand Down Expand Up @@ -583,18 +582,33 @@ impl<'tcx> Validator<'_, 'tcx> {
}

fn validate_rvalue(&self, rvalue: &Rvalue<'tcx>) -> Result<(), Unpromotable> {
match *rvalue {
Rvalue::Cast(CastKind::Misc, ref operand, cast_ty) => {
let operand_ty = operand.ty(self.body, self.tcx);
let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
if let (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) = (cast_in, cast_out) {
// ptr-to-int casts are not possible in consts and thus not promotable
return Err(Unpromotable);
match rvalue {
Rvalue::Use(operand) | Rvalue::Repeat(operand, _) | Rvalue::UnaryOp(_, operand) => {
self.validate_operand(operand)?;
}

Rvalue::Discriminant(place) | Rvalue::Len(place) => self.validate_place(place.as_ref())?,

Rvalue::ThreadLocalRef(_) => return Err(Unpromotable),

Rvalue::Cast(kind, operand, cast_ty) => {
if matches!(kind, CastKind::Misc) {
let operand_ty = operand.ty(self.body, self.tcx);
let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
if let (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) = (cast_in, cast_out) {
// ptr-to-int casts are not possible in consts and thus not promotable
return Err(Unpromotable);
}
// int-to-ptr casts are fine, they just use the integer value at pointer type.
}

self.validate_operand(operand)?;
}

Rvalue::BinaryOp(op, ref lhs, _) => {
Rvalue::BinaryOp(op, lhs, rhs)
| Rvalue::CheckedBinaryOp(op, lhs, rhs) => {
let op = *op;
if let ty::RawPtr(_) | ty::FnPtr(..) = lhs.ty(self.body, self.tcx).kind() {
assert!(
op == BinOp::Eq
Expand All @@ -609,29 +623,17 @@ impl<'tcx> Validator<'_, 'tcx> {
// raw pointer operations are not allowed inside consts and thus not promotable
return Err(Unpromotable);
}
}

Rvalue::NullaryOp(NullOp::Box, _) => return Err(Unpromotable),

// FIXME(RalfJung): the rest is *implicitly considered promotable*... that seems dangerous.
_ => {}
}

match rvalue {
Rvalue::ThreadLocalRef(_) => Err(Unpromotable),

Rvalue::NullaryOp(..) => Ok(()),

Rvalue::Discriminant(place) | Rvalue::Len(place) => self.validate_place(place.as_ref()),
// FIXME: reject operations that can fail -- namely, division and modulo.

Rvalue::Use(operand)
| Rvalue::Repeat(operand, _)
| Rvalue::UnaryOp(_, operand)
| Rvalue::Cast(_, operand, _) => self.validate_operand(operand),

Rvalue::BinaryOp(_, lhs, rhs) | Rvalue::CheckedBinaryOp(_, lhs, rhs) => {
self.validate_operand(lhs)?;
self.validate_operand(rhs)
self.validate_operand(rhs)?;
}

Rvalue::NullaryOp(op, _) => {
if matches!(op, NullOp::Box) {
return Err(Unpromotable);
}
}

Rvalue::AddressOf(_, place) => {
Expand All @@ -646,16 +648,18 @@ impl<'tcx> Validator<'_, 'tcx> {
});
}
}
Err(Unpromotable)
return Err(Unpromotable);
}

Rvalue::Ref(_, kind, place) => {
// Special-case reborrows to be more like a copy of the reference.
let mut place_simplified = place.as_ref();
if let [proj_base @ .., ProjectionElem::Deref] = &place_simplified.projection {
let base_ty = Place::ty_from(place_simplified.local, proj_base, self.body, self.tcx).ty;
let base_ty =
Place::ty_from(place_simplified.local, proj_base, self.body, self.tcx).ty;
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huh what happened here?

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Just rustfmt, or is there any other difference that I am missing?

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yea, but I was confused why rustfmt would do this.

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Because it is being rustfmt? ;)

The variable name got longer, since I need to keep the original place around. As a result this line crossed the threshold.

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oh... this is due to an intermediate state that was reverted later? Because this specific line is exactly the same (modulo whitespace) as the line that was there before.

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Maybe I didn't fmt between all commits.

if let ty::Ref(..) = base_ty.kind() {
place_simplified = PlaceRef { local: place_simplified.local, projection: proj_base };
place_simplified =
PlaceRef { local: place_simplified.local, projection: proj_base };
}
}

Expand All @@ -664,18 +668,16 @@ impl<'tcx> Validator<'_, 'tcx> {
// Check that the reference is fine (using the original place!).
// (Needs to come after `validate_local` to avoid ICEs.)
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self.validate_ref(*kind, place)?;

Ok(())
}

Rvalue::Aggregate(_, ref operands) => {
Rvalue::Aggregate(_, operands) => {
for o in operands {
self.validate_operand(o)?;
}

Ok(())
}
}

Ok(())
}

fn validate_call(
Expand Down