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mir: don't attempt to promote Unpromotable constant temps.

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This commit is contained in:
Eduard Burtescu 2016-05-10 21:26:34 +03:00
parent d6588097d4
commit e5a91b7ba1
2 changed files with 42 additions and 6 deletions
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24
src/librustc_mir/transform/qualify_consts.rs
View File

@ -65,13 +65,18 @@ bitflags! {
// pointer comparisons, ptr-to-int casts, etc.
const NOT_CONST = 1 << 6,
// Refers to temporaries which cannot be promoted as
// promote_consts decided they weren't simple enough.
const NOT_PROMOTABLE = 1 << 7,
// Borrows of temporaries can be promoted only
// if they have none of the above qualifications.
const UNPROMOTABLE = !0,
const NEVER_PROMOTE = !0,
// Const items can only have MUTABLE_INTERIOR
// without producing an error.
const CONST_ERROR = !Qualif::MUTABLE_INTERIOR.bits
// and NOT_PROMOTABLE without producing an error.
const CONST_ERROR = !Qualif::MUTABLE_INTERIOR.bits &
!Qualif::NOT_PROMOTABLE.bits
}
}
@ -502,6 +507,10 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx> {
self.add(Qualif::NOT_CONST);
}
Lvalue::Temp(index) => {
if !self.temp_promotion_state[index as usize].is_promotable() {
self.add(Qualif::NOT_PROMOTABLE);
}
if let Some(qualif) = self.temp_qualif[index as usize] {
self.add(qualif);
} else {
@ -687,8 +696,11 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx> {
// We might have a candidate for promotion.
let candidate = Candidate::Ref(self.location);
if self.mode == Mode::Fn || self.mode == Mode::ConstFn {
if !self.qualif.intersects(Qualif::UNPROMOTABLE) {
self.promotion_candidates.push(candidate);
if !self.qualif.intersects(Qualif::NEVER_PROMOTE) {
// We can only promote direct borrows of temps.
if let Lvalue::Temp(_) = *lvalue {
self.promotion_candidates.push(candidate);
}
}
}
}
@ -780,7 +792,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx> {
this.visit_operand(arg);
if is_shuffle && i == 2 && this.mode == Mode::Fn {
let candidate = Candidate::ShuffleIndices(bb);
if !this.qualif.intersects(Qualif::UNPROMOTABLE) {
if !this.qualif.intersects(Qualif::NEVER_PROMOTE) {
this.promotion_candidates.push(candidate);
} else {
span_err!(this.tcx.sess, this.span, E0526,

24
src/test/run-pass/issue-33537.rs Normal file
View File

@ -0,0 +1,24 @@
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![feature(const_fn)]
const fn foo() -> *const i8 {
b"foo" as *const _ as *const i8
}
const fn bar() -> i32 {
*&{(1, 2, 3).1}
}
fn main() {
assert_eq!(foo(), b"foo" as *const _ as *const i8);
assert_eq!(bar(), 2);
}