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Auto merge of #43859 - arielb1:nonfree-block-live, r=nagisa

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emit StorageLive for box temporaries

We started emitting StorageDead, so we better emit the corrseponding
StorageLive to avoid problems.

cc #43772 solson/miri#303
This commit is contained in:
bors 2017-08-15 04:32:17 +00:00
commit f6a30bd37b
2 changed files with 97 additions and 3 deletions
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12
src/librustc_mir/build/expr/as_rvalue.rs
View File

@ -97,13 +97,19 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
ExprKind::Box { value } => {
let value = this.hir.mirror(value);
let result = this.temp(expr.ty, expr_span);
// to start, malloc some memory of suitable type (thus far, uninitialized):
let box_ = Rvalue::NullaryOp(NullOp::Box, value.ty);
this.cfg.push_assign(block, source_info, &result, box_);
if let Some(scope) = scope {
// schedule a shallow free of that memory, lest we unwind:
this.cfg.push(block, Statement {
source_info: source_info,
kind: StatementKind::StorageLive(result.clone())
});
this.schedule_drop(expr_span, scope, &result, value.ty);
}
// malloc some memory of suitable type (thus far, uninitialized):
let box_ = Rvalue::NullaryOp(NullOp::Box, value.ty);
this.cfg.push_assign(block, source_info, &result, box_);
// initialize the box contents:
unpack!(block = this.into(&result.clone().deref(), block, value));
block.and(Rvalue::Use(Operand::Consume(result)))

88
src/test/mir-opt/box_expr.rs Normal file
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@ -0,0 +1,88 @@
// Copyright 2017 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(box_syntax)]
fn main() {
let x = box S::new();
drop(x);
}
struct S;
impl S {
fn new() -> Self { S }
}
impl Drop for S {
fn drop(&mut self) {
println!("splat!");
}
}
// END RUST SOURCE
// START rustc.node4.ElaborateDrops.before.mir
// let mut _0: ();
// let _1: std::boxed::Box<S>;
// let mut _2: std::boxed::Box<S>;
// let mut _3: ();
// let mut _4: std::boxed::Box<S>;
//
// bb0: {
// StorageLive(_1);
// StorageLive(_2);
// _2 = Box(S);
// (*_2) = const S::new() -> [return: bb1, unwind: bb3];
// }
//
// bb1: {
// _1 = _2;
// drop(_2) -> bb4;
// }
//
// bb2: {
// resume;
// }
//
// bb3: {
// drop(_2) -> bb2;
// }
//
// bb4: {
// StorageDead(_2);
// StorageLive(_4);
// _4 = _1;
// _3 = const std::mem::drop(_4) -> [return: bb5, unwind: bb7];
// }
//
// bb5: {
// drop(_4) -> [return: bb8, unwind: bb6];
// }
//
// bb6: {
// drop(_1) -> bb2;
// }
//
// bb7: {
// drop(_4) -> bb6;
// }
//
// bb8: {
// StorageDead(_4);
// _0 = ();
// drop(_1) -> bb9;
// }
//
// bb9: {
// StorageDead(_1);
// return;
// }
// }
// END rustc.node4.ElaborateDrops.before.mir