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never promote non-const operations; revert STATIC promotion change

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This commit is contained in:
Ralf Jung 2020-09-09 10:00:23 +02:00
parent 7febd5a257
commit 7b99c8e1cf
1 changed files with 14 additions and 4 deletions
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18
compiler/rustc_mir/src/transform/promote_consts.rs
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@ -584,6 +584,16 @@ impl<'tcx> Validator<'_, 'tcx> {
// `validate_rvalue` upon access.
Operand::Constant(c) => {
if let Some(def_id) = c.check_static_ptr(self.tcx) {
// Only allow statics (not consts) to refer to other statics.
// FIXME(eddyb) does this matter at all for promotion?
// FIXME(RalfJung) it makes little sense to not promote this in `fn/`const fn`,
// and in `const` this cannot occur anyway. The concern is that we might promote
// even `let x = &STATIC` which would be useless.
let is_static = matches!(self.const_kind, Some(hir::ConstContext::Static(_)));
if !is_static {
return Err(Unpromotable);
}
let is_thread_local = self.tcx.is_thread_local_static(def_id);
if is_thread_local {
return Err(Unpromotable);
@ -597,20 +607,20 @@ impl<'tcx> Validator<'_, 'tcx> {
fn validate_rvalue(&self, rvalue: &Rvalue<'tcx>) -> Result<(), Unpromotable> {
match *rvalue {
Rvalue::Cast(CastKind::Misc, ref operand, cast_ty) if self.maybe_runtime() => {
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");
match (cast_in, cast_out) {
(CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) => {
// ptr-to-int casts are not promotable
// ptr-to-int casts are not possible in consts and thus not promotable
return Err(Unpromotable);
}
_ => {}
}
}
Rvalue::BinaryOp(op, ref lhs, _) if self.maybe_runtime() => {
Rvalue::BinaryOp(op, ref lhs, _) => {
if let ty::RawPtr(_) | ty::FnPtr(..) = lhs.ty(self.body, self.tcx).kind() {
assert!(
op == BinOp::Eq
@ -622,7 +632,7 @@ impl<'tcx> Validator<'_, 'tcx> {
|| op == BinOp::Offset
);
// raw pointer operations are not allowed inside promoteds
// raw pointer operations are not allowed inside consts and thus not promotable
return Err(Unpromotable);
}
}