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Auto merge of #44129 - pnkfelix:fix-end-region-emission-order, r=nmatsakis

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Fix end region emission order

Fix #43481
This commit is contained in:
bors 2017-09-13 13:01:42 +00:00
commit 539f2083de
14 changed files with 319 additions and 23 deletions
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10
src/librustc_mir/build/scope.rs
View file

@ -352,6 +352,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
}
let scope = self.scopes.pop().unwrap();
assert_eq!(scope.region_scope, region_scope.0);
self.cfg.push_end_region(self.hir.tcx(), block, region_scope.1, scope.region_scope);
unpack!(block = build_scope_drops(&mut self.cfg,
&scope,
&self.scopes,
@ -359,7 +361,6 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
self.arg_count,
false));
self.cfg.push_end_region(self.hir.tcx(), block, region_scope.1, scope.region_scope);
block.unit()
}
@ -406,15 +407,16 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
scope.cached_exits.insert((target, region_scope.0), b);
b
};
// End all regions for scopes out of which we are breaking.
self.cfg.push_end_region(self.hir.tcx(), block, region_scope.1, scope.region_scope);
unpack!(block = build_scope_drops(&mut self.cfg,
scope,
rest,
block,
self.arg_count,
false));
// End all regions for scopes out of which we are breaking.
self.cfg.push_end_region(self.hir.tcx(), block, region_scope.1, scope.region_scope);
}
}
let scope = &self.scopes[len - scope_count];

2
src/test/mir-opt/end_region_1.rs
View file

@ -30,8 +30,8 @@ fn main() {
// StorageLive(_2);
// _2 = &'10_1rs _1;
// _0 = ();
// StorageDead(_2);
// EndRegion('10_1rs);
// StorageDead(_2);
// StorageDead(_1);
// return;
// }

6
src/test/mir-opt/end_region_2.rs
View file

@ -46,8 +46,8 @@ fn main() {
// bb2: {
// _0 = ();
// StorageDead(_5);
// StorageDead(_3);
// EndRegion('23_1rs);
// StorageDead(_3);
// StorageDead(_2);
// return;
// }
@ -56,10 +56,10 @@ fn main() {
// StorageLive(_7);
// _7 = &'23_3rs _2;
// _1 = ();
// StorageDead(_7);
// EndRegion('23_3rs);
// StorageDead(_3);
// StorageDead(_7);
// EndRegion('23_1rs);
// StorageDead(_3);
// StorageDead(_2);
// goto -> bb1;
// }

6
src/test/mir-opt/end_region_3.rs
View file

@ -49,8 +49,8 @@ fn main() {
// bb2: {
// _0 = ();
// StorageDead(_5);
// StorageDead(_3);
// EndRegion('26_1rs);
// StorageDead(_3);
// StorageDead(_1);
// return;
// }
@ -60,10 +60,10 @@ fn main() {
// StorageLive(_7);
// _7 = &'26_3rs _1;
// _2 = ();
// StorageDead(_7);
// EndRegion('26_3rs);
// StorageDead(_3);
// StorageDead(_7);
// EndRegion('26_1rs);
// StorageDead(_3);
// goto -> bb1;
// }
// END rustc.node4.SimplifyCfg-qualify-consts.after.mir

4
src/test/mir-opt/end_region_4.rs
View file

@ -53,10 +53,10 @@ fn foo(i: i32) {
// StorageLive(_6);
// _6 = &'26_4rs _2;
// _0 = ();
// StorageDead(_6);
// EndRegion('26_4rs);
// StorageDead(_3);
// StorageDead(_6);
// EndRegion('26_2rs);
// StorageDead(_3);
// StorageDead(_2);
// drop(_1) -> bb4;
// }

2
src/test/mir-opt/end_region_5.rs
View file

@ -44,8 +44,8 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// _2 = const foo(_3) -> [return: bb1, unwind: bb3];
// }
// bb1: {
// StorageDead(_3);
// EndRegion('14s);
// StorageDead(_3);
// _0 = ();
// drop(_1) -> bb4;
// }

4
src/test/mir-opt/end_region_6.rs
View file

@ -44,8 +44,8 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// _2 = const foo(_3) -> [return: bb1, unwind: bb3];
// }
// bb1: {
// StorageDead(_3);
// EndRegion('19s);
// StorageDead(_3);
// _0 = ();
// drop(_1) -> bb4;
// }
@ -75,8 +75,8 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// _3 = ((*_2).0: i32);
// _0 = _3;
// StorageDead(_3);
// StorageDead(_2);
// EndRegion('15_0rs);
// StorageDead(_2);
// return;
// }
// END rustc.node22.SimplifyCfg-qualify-consts.after.mir

2
src/test/mir-opt/end_region_7.rs
View file

@ -84,8 +84,8 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// _3 = ((*_2).0: i32);
// _0 = _3;
// StorageDead(_3);
// StorageDead(_2);
// EndRegion('15_0rs);
// StorageDead(_2);
// drop(_1) -> bb1;
// }
// bb1: {

2
src/test/mir-opt/end_region_8.rs
View file

@ -50,8 +50,8 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
// bb1: {
// StorageDead(_4);
// _0 = ();
// StorageDead(_2);
// EndRegion('21_1rs);
// StorageDead(_2);
// drop(_1) -> bb4;
// }
// bb2: {

7
src/test/mir-opt/end_region_9.rs
View file

@ -42,7 +42,7 @@ fn main() {
// let mut _0: ();
// let mut _1: bool;
// let _2: i32;
// let mut _4: &'13_0rs i32;
// let mut _4: &'33_0rs i32;
// let mut _3: ();
// let mut _5: !;
// let mut _6: ();
@ -67,15 +67,15 @@ fn main() {
// bb2: {
// _0 = ();
// StorageDead(_7);
// EndRegion('33_0rs);
// StorageDead(_4);
// EndRegion('13_0rs);
// StorageDead(_2);
// StorageDead(_1);
// return;
// }
//
// bb3: {
// _4 = &'13_0rs _2;
// _4 = &'33_0rs _2;
// _6 = ();
// StorageDead(_7);
// _1 = const true;
@ -83,3 +83,4 @@ fn main() {
// goto -> bb1;
// }
// }
// END rustc.node4.SimplifyCfg-qualify-consts.after.mir

132
src/test/mir-opt/end_region_cyclic.rs Normal file
View file

@ -0,0 +1,132 @@
// 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.
// compile-flags: -Z identify_regions -Z span_free_formats -Z emit-end-regions
// ignore-tidy-linelength
// This test models a scenario with a cyclic reference. Rust obviously
// needs to handle such cases.
//
// The interesting part about this test is that such case shows that
// one cannot generally force all references to be dead before you hit
// their EndRegion; at least, not without breaking the more important
// property that all borrowed storage locations have their regions
// ended strictly before their StorageDeads. (This test was inspired
// by discussion on Issue #43481.)
use std::cell::Cell;
struct S<'a> {
r: Cell<Option<&'a S<'a>>>,
}
fn main() {
loop {
let x = S { r: Cell::new(None) };
x.r.set(Some(&x));
if query() { break; }
x.r.set(Some(&x));
}
}
fn query() -> bool { true }
// END RUST SOURCE
// START rustc.node16.SimplifyCfg-qualify-consts.after.mir
// fn main() -> () {
// let mut _0: ();
// scope 1 {
// let _2: S<'35_0rs>;
// }
// let mut _1: ();
// let mut _3: std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>;
// let mut _4: std::option::Option<&'35_0rs S<'35_0rs>>;
// let mut _5: ();
// let mut _6: &'16s std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>;
// let mut _7: std::option::Option<&'35_0rs S<'35_0rs>>;
// let mut _8: &'35_0rs S<'35_0rs>;
// let mut _9: &'35_0rs S<'35_0rs>;
// let mut _10: ();
// let mut _11: bool;
// let mut _12: !;
// let mut _13: ();
// let mut _14: &'33s std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>;
// let mut _15: std::option::Option<&'35_0rs S<'35_0rs>>;
// let mut _16: &'35_0rs S<'35_0rs>;
// let mut _17: &'35_0rs S<'35_0rs>;
// bb0: {
// goto -> bb1;
// }
// bb1: {
// StorageLive(_2);
// StorageLive(_3);
// StorageLive(_4);
// _4 = std::option::Option<&'35_0rs S<'35_0rs>>::None;
// _3 = const <std::cell::Cell<T>>::new(_4) -> bb2;
// }
// bb2: {
// StorageDead(_4);
// _2 = S<'35_0rs> { r: _3 };
// StorageDead(_3);
// StorageLive(_6);
// _6 = &'16s (_2.0: std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>);
// StorageLive(_7);
// StorageLive(_8);
// StorageLive(_9);
// _9 = &'35_0rs _2;
// _8 = &'35_0rs (*_9);
// _7 = std::option::Option<&'35_0rs S<'35_0rs>>::Some(_8,);
// StorageDead(_8);
// _5 = const <std::cell::Cell<T>>::set(_6, _7) -> bb3;
// }
// bb3: {
// EndRegion('16s);
// StorageDead(_7);
// StorageDead(_6);
// StorageDead(_9);
// StorageLive(_11);
// _11 = const query() -> bb4;
// }
// bb4: {
// switchInt(_11) -> [0u8: bb6, otherwise: bb5];
// }
// bb5: {
// _0 = ();
// StorageDead(_11);
// EndRegion('35_0rs);
// StorageDead(_2);
// return;
// }
// bb6: {
// _10 = ();
// StorageDead(_11);
// StorageLive(_14);
// _14 = &'33s (_2.0: std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>);
// StorageLive(_15);
// StorageLive(_16);
// StorageLive(_17);
// _17 = &'35_0rs _2;
// _16 = &'35_0rs (*_17);
// _15 = std::option::Option<&'35_0rs S<'35_0rs>>::Some(_16,);
// StorageDead(_16);
// _13 = const <std::cell::Cell<T>>::set(_14, _15) -> bb7;
// }
// bb7: {
// EndRegion('33s);
// StorageDead(_15);
// StorageDead(_14);
// StorageDead(_17);
// _1 = ();
// EndRegion('35_0rs);
// StorageDead(_2);
// goto -> bb1;
// }
// }
// END rustc.node16.SimplifyCfg-qualify-consts.after.mir

161
src/test/mir-opt/end_region_destruction_extents_1.rs Normal file
View file

@ -0,0 +1,161 @@
// 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.
// compile-flags: -Z identify_regions -Z span_free_formats -Z emit-end-regions
// ignore-tidy-linelength
// A scenario with significant destruction code extents (which have
// suffix "dce" in current `-Z identify_regions` rendering).
#![feature(generic_param_attrs)]
#![feature(dropck_eyepatch)]
fn main() {
// Since the second param to `D1` is may_dangle, it is legal for
// the region of that parameter to end before the drop code for D1
// is executed.
(D1(&S1("ex1"), &S1("dang1"))).0;
}
#[derive(Debug)]
struct S1(&'static str);
#[derive(Debug)]
struct D1<'a, 'b>(&'a S1, &'b S1);
// The `#[may_dangle]` means that references of type `&'b _` may be
// invalid during the execution of this destructor; i.e. in this case
// the destructor code is not allowed to read or write `*self.1`, while
// it can read/write `*self.0`.
unsafe impl<'a, #[may_dangle] 'b> Drop for D1<'a, 'b> {
fn drop(&mut self) {
println!("D1({:?}, _)", self.0);
}
}
// Notes on the MIR output below:
//
// 1. The `EndRegion('10s)` is allowed to precede the `drop(_3)`
// solely because of the #[may_dangle] mentioned above.
//
// 2. Regarding the occurrence of `EndRegion('12ds)` *after* `StorageDead(_6)`
// (where we have borrows `&'12ds _6`): Eventually:
//
// i. this code should be rejected (by mir-borrowck), or
//
// ii. the MIR code generation should be changed so that the
// EndRegion('12ds)` precedes `StorageDead(_6)` in the
// control-flow. (Note: arielb1 views drop+storagedead as one
// unit, and does not see this option as a useful avenue to
// explore.), or
//
// iii. the presence of EndRegion should be made irrelevant by a
// transformation encoding the effects of rvalue-promotion.
// This may be the simplest and most-likely option; note in
// particular that `StorageDead(_6)` goes away below in
// rustc.node4.QualifyAndPromoteConstants.after.mir
// END RUST SOURCE
// START rustc.node4.QualifyAndPromoteConstants.before.mir
// fn main() -> () {
// let mut _0: ();
// let mut _1: &'12ds S1;
// let mut _2: &'12ds S1;
// let mut _3: D1<'12ds, '10s>;
// let mut _4: &'12ds S1;
// let mut _5: &'12ds S1;
// let mut _6: S1;
// let mut _7: &'10s S1;
// let mut _8: &'10s S1;
// let mut _9: S1;
//
// bb0: {
// StorageLive(_2);
// StorageLive(_3);
// StorageLive(_4);
// StorageLive(_5);
// StorageLive(_6);
// _6 = S1::{{constructor}}(const "ex1",);
// _5 = &'12ds _6;
// _4 = &'12ds (*_5);
// StorageLive(_7);
// StorageLive(_8);
// StorageLive(_9);
// _9 = S1::{{constructor}}(const "dang1",);
// _8 = &'10s _9;
// _7 = &'10s (*_8);
// _3 = D1<'12ds, '10s>::{{constructor}}(_4, _7);
// EndRegion('10s);
// StorageDead(_7);
// StorageDead(_4);
// _2 = (_3.0: &'12ds S1);
// _1 = _2;
// StorageDead(_2);
// drop(_3) -> bb1;
// }
//
// bb1: {
// StorageDead(_3);
// StorageDead(_8);
// StorageDead(_9);
// StorageDead(_5);
// StorageDead(_6);
// EndRegion('12ds);
// _0 = ();
// return;
// }
// }
// END rustc.node4.QualifyAndPromoteConstants.before.mir
// START rustc.node4.QualifyAndPromoteConstants.after.mir
// fn main() -> () {
// let mut _0: ();
// let mut _1: &'12ds S1;
// let mut _2: &'12ds S1;
// let mut _3: D1<'12ds, '10s>;
// let mut _4: &'12ds S1;
// let mut _5: &'12ds S1;
// let mut _6: S1;
// let mut _7: &'10s S1;
// let mut _8: &'10s S1;
// let mut _9: S1;
//
// bb0: {
// StorageLive(_2);
// StorageLive(_3);
// StorageLive(_4);
// StorageLive(_5);
// _5 = promoted1;
// _4 = &'12ds (*_5);
// StorageLive(_7);
// StorageLive(_8);
// _8 = promoted0;
// _7 = &'10s (*_8);
// _3 = D1<'12ds, '10s>::{{constructor}}(_4, _7);
// EndRegion('10s);
// StorageDead(_7);
// StorageDead(_4);
// _2 = (_3.0: &'12ds S1);
// _1 = _2;
// StorageDead(_2);
// drop(_3) -> bb1;
// }
//
// bb1: {
// StorageDead(_3);
// StorageDead(_8);
// StorageDead(_5);
// EndRegion('12ds);
// _0 = ();
// return;
// }
// }
// END rustc.node4.QualifyAndPromoteConstants.after.mir

2
src/test/mir-opt/validate_1.rs
View file

@ -68,8 +68,8 @@ fn main() {
// _5 = (*_4);
// _0 = _5;
// StorageDead(_5);
// StorageDead(_4);
// EndRegion(ReScope(Remainder(BlockRemainder { block: ItemLocalId(22), first_statement_index: 0 })));
// StorageDead(_4);
// StorageDead(_3);
// return;
// }

2
src/test/mir-opt/validate_5.rs
View file

@ -54,8 +54,8 @@ fn main() {
// _5 = &ReErased mut (*_3);
// Validate(Acquire, [(*_5): i32/ReScope(Node(ItemLocalId(9)))]);
// _4 = _5 as *mut i32 (Misc);
// StorageDead(_5);
// EndRegion(ReScope(Node(ItemLocalId(9))));
// StorageDead(_5);
// Validate(Release, [_0: bool, _4: *mut i32]);
// _0 = const write_42(_4) -> bb1;
// }