Auto merge of #55316 - RalfJung:retagging, r=oli-obk

Add Retagging statements

This adds a `Retag` statement kind to MIR, used to perform the retagging operation from [Stacked Borrows](https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html). It also kills the old `Validate` statements that I added last year.

NOTE: This includes https://github.com/rust-lang/rust/pull/55270. Only [these commits are new](https://github.com/RalfJung/rust/compare/stacked-borrows-ng...RalfJung:retagging).

7 files changed, 151 insertions, 349 deletions

diff --git a/src/test/mir-opt/inline-retag.rs b/src/test/mir-opt/inline-retag.rs
new file mode 100644
index 00000000000..4b3280ee561
--- /dev/null
+++ b/src/test/mir-opt/inline-retag.rs
@@ -0,0 +1,45 @@
+// 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 span_free_formats -Z mir-emit-retag
+
+// Tests that MIR inliner fixes up `Retag`'s `fn_entry` flag
+
+fn main() {
+    println!("{}", bar());
+}
+
+#[inline(always)]
+fn foo(x: &i32, y: &i32) -> bool {
+    *x == *y
+}
+
+fn bar() -> bool {
+    let f = foo;
+    f(&1, &-1)
+}
+
+// END RUST SOURCE
+// START rustc.bar.Inline.after.mir
+// ...
+//     bb0: {
+//         ...
+//         Retag(_3);
+//         Retag(_6);
+//         StorageLive(_9);
+//         _9 = (*_3);
+//         StorageLive(_10);
+//         _10 = (*_6);
+//         _0 = Eq(move _9, move _10);
+//         ...
+//         return;
+//     }
+// ...
+// END rustc.bar.Inline.after.mir
diff --git a/src/test/mir-opt/retag.rs b/src/test/mir-opt/retag.rs
new file mode 100644
index 00000000000..9c013008ab2
--- /dev/null
+++ b/src/test/mir-opt/retag.rs
@@ -0,0 +1,106 @@
+// 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.
+
+// ignore-tidy-linelength
+// compile-flags: -Z mir-emit-retag -Z mir-opt-level=0 -Z span_free_formats
+
+#![allow(unused)]
+
+struct Test(i32);
+
+impl Test {
+    // Make sure we run the pass on a method, not just on bare functions.
+    fn foo<'x>(&self, x: &'x mut i32) -> &'x mut i32 { x }
+    fn foo_shr<'x>(&self, x: &'x i32) -> &'x i32 { x }
+}
+
+fn main() {
+    let mut x = 0;
+    {
+        let v = Test(0).foo(&mut x); // just making sure we do not panic when there is a tuple struct ctor
+        let w = { v }; // assignment
+        let _w = w; // reborrow
+    }
+
+    // Also test closures
+    let c: fn(&i32) -> &i32 = |x: &i32| -> &i32 { let _y = x; x };
+    let _w = c(&x);
+
+    // need to call `foo_shr` or it doesn't even get generated
+    Test(0).foo_shr(&0);
+}
+
+// END RUST SOURCE
+// START rustc.{{impl}}-foo.EraseRegions.after.mir
+//     bb0: {
+//         Retag([fn entry] _1);
+//         Retag([fn entry] _2);
+//         ...
+//         _0 = &mut (*_3);
+//         ...
+//         return;
+//     }
+// END rustc.{{impl}}-foo.EraseRegions.after.mir
+// START rustc.{{impl}}-foo_shr.EraseRegions.after.mir
+//     bb0: {
+//         Retag([fn entry] _1);
+//         Retag([fn entry] _2);
+//         ...
+//         _0 = _2;
+//         Retag(_0);
+//         ...
+//         return;
+//     }
+// END rustc.{{impl}}-foo_shr.EraseRegions.after.mir
+// START rustc.main.EraseRegions.after.mir
+// fn main() -> () {
+//     ...
+//     bb0: {
+//         ...
+//         _3 = const Test::foo(move _4, move _6) -> bb1;
+//     }
+//
+//     bb1: {
+//         Retag(_3);
+//         ...
+//         _9 = move _3;
+//         Retag(_9);
+//         _8 = &mut (*_9);
+//         StorageDead(_9);
+//         StorageLive(_10);
+//         _10 = move _8;
+//         Retag(_10);
+//         ...
+//         _13 = move _14(move _15) -> bb2;
+//     }
+//
+//     bb2: {
+//         Retag(_13);
+//         ...
+//     }
+//     ...
+// }
+// END rustc.main.EraseRegions.after.mir
+// START rustc.main-{{closure}}.EraseRegions.after.mir
+// fn main::{{closure}}(_1: &[closure@NodeId(117)], _2: &i32) -> &i32 {
+//     ...
+//     bb0: {
+//         Retag([fn entry] _1);
+//         Retag([fn entry] _2);
+//         StorageLive(_3);
+//         _3 = _2;
+//         Retag(_3);
+//         _0 = _2;
+//         Retag(_0);
+//         StorageDead(_3);
+//         return;
+//     }
+// }
+// END rustc.main-{{closure}}.EraseRegions.after.mir
diff --git a/src/test/mir-opt/validate_1.rs b/src/test/mir-opt/validate_1.rs
deleted file mode 100644
index f1544968adb..00000000000
--- a/src/test/mir-opt/validate_1.rs
+++ /dev/null
@@ -1,76 +0,0 @@
-// 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.
-
-// ignore-tidy-linelength
-// compile-flags: -Z verbose -Z mir-emit-validate=1 -Z span_free_formats
-
-struct Test(i32);
-
-impl Test {
-    // Make sure we run the pass on a method, not just on bare functions.
-    fn foo(&self, _x: &mut i32) {}
-}
-
-fn main() {
-    let mut x = 0;
-    Test(0).foo(&mut x); // just making sure we do not panic when there is a tuple struct ctor
-
-    // Also test closures
-    let c = |x: &mut i32| { let y = &*x; *y };
-    c(&mut x);
-}
-
-// END RUST SOURCE
-// START rustc.{{impl}}-foo.EraseRegions.after.mir
-//     bb0: {
-//         Validate(Acquire, [_1: &ReFree(DefId(0/0:5 ~ validate_1[317d]::{{impl}}[0]::foo[0]), BrAnon(0)) Test, _2: &ReFree(DefId(0/0:5 ~ validate_1[317d]::{{impl}}[0]::foo[0]), BrAnon(1)) mut i32]);
-//         ...
-//         return;
-//     }
-// END rustc.{{impl}}-foo.EraseRegions.after.mir
-// START rustc.main.EraseRegions.after.mir
-// fn main() -> () {
-//     ...
-//     bb0: {
-//         ...
-//         Validate(Suspend(ReScope(Node(ItemLocalId(13)))), [_1: i32]);
-//         _6 = &ReErased mut _1;
-//         Validate(Acquire, [(*_6): i32/ReScope(Node(ItemLocalId(13)))]);
-//         Validate(Suspend(ReScope(Node(ItemLocalId(13)))), [(*_6): i32/ReScope(Node(ItemLocalId(13)))]);
-//         _5 = &ReErased mut (*_6);
-//         Validate(Acquire, [(*_5): i32/ReScope(Node(ItemLocalId(13)))]);
-//         Validate(Release, [_2: (), _3: &ReScope(Node(ItemLocalId(13))) Test, _5: &ReScope(Node(ItemLocalId(13))) mut i32]);
-//         _2 = const Test::foo(move _3, move _5) -> bb1;
-//     }
-//
-//     bb1: {
-//         Validate(Acquire, [_2: ()]);
-//         EndRegion(ReScope(Node(ItemLocalId(13))));
-//         ...
-//         return;
-//     }
-// }
-// END rustc.main.EraseRegions.after.mir
-// START rustc.main-{{closure}}.EraseRegions.after.mir
-// fn main::{{closure}}(_1: &ReErased [closure@NodeId(65)], _2: &ReErased mut i32) -> i32 {
-//     ...
-//     bb0: {
-//         Validate(Acquire, [_1: &ReFree(DefId(0/1:11 ~ validate_1[317d]::main[0]::{{closure}}[0]), BrEnv) [closure@NodeId(65)], _2: &ReFree(DefId(0/1:11 ~ validate_1[317d]::main[0]::{{closure}}[0]), BrAnon(0)) mut i32]);
-//         StorageLive(_3);
-//         Validate(Suspend(ReScope(Remainder { block: ItemLocalId(31), first_statement_index: 0 })), [(*_2): i32]);
-//         _3 = &ReErased (*_2);
-//         Validate(Acquire, [(*_3): i32/ReScope(Remainder { block: ItemLocalId(31), first_statement_index: 0 }) (imm)]);
-//         _0 = (*_3);
-//         EndRegion(ReScope(Remainder { block: ItemLocalId(31), first_statement_index: 0 }));
-//         StorageDead(_3);
-//         return;
-//     }
-// }
-// END rustc.main-{{closure}}.EraseRegions.after.mir
diff --git a/src/test/mir-opt/validate_2.rs b/src/test/mir-opt/validate_2.rs
deleted file mode 100644
index 3776a11b3ab..00000000000
--- a/src/test/mir-opt/validate_2.rs
+++ /dev/null
@@ -1,37 +0,0 @@
-// 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.
-
-// ignore-tidy-linelength
-// ignore-wasm32-bare unwinding being disabled causes differences in output
-// ignore-wasm64-bare unwinding being disabled causes differences in output
-// compile-flags: -Z verbose -Z mir-emit-validate=1
-
-fn main() {
-    let _x : Box<[i32]> = Box::new([1, 2, 3]);
-}
-
-// END RUST SOURCE
-// START rustc.main.EraseRegions.after.mir
-// fn main() -> () {
-//     ...
-//     bb1: {
-//         Validate(Acquire, [_2: std::boxed::Box<[i32; 3]>]);
-//         Validate(Release, [_2: std::boxed::Box<[i32; 3]>]);
-//         _1 = move _2 as std::boxed::Box<[i32]> (Unsize);
-//         Validate(Acquire, [_1: std::boxed::Box<[i32]>]);
-//         StorageDead(_2);
-//         StorageDead(_3);
-//         _0 = ();
-//         Validate(Release, [_1: std::boxed::Box<[i32]>]);
-//         drop(_1) -> [return: bb2, unwind: bb3];
-//     }
-//     ...
-// }
-// END rustc.main.EraseRegions.after.mir
diff --git a/src/test/mir-opt/validate_3.rs b/src/test/mir-opt/validate_3.rs
deleted file mode 100644
index ce840397713..00000000000
--- a/src/test/mir-opt/validate_3.rs
+++ /dev/null
@@ -1,77 +0,0 @@
-// 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.
-
-// ignore-tidy-linelength
-// compile-flags: -Z verbose -Z mir-emit-validate=1
-
-struct Test {
-    x: i32
-}
-
-fn foo(_x: &i32) {}
-
-fn main() {
-    // These internal unsafe functions should have no effect on the code generation.
-    unsafe fn _unused1() {}
-    fn _unused2(x: *const i32) -> i32 { unsafe { *x }}
-
-    let t = Test { x: 0 };
-    let t = &t;
-    foo(&t.x);
-}
-
-// END RUST SOURCE
-// START rustc.main.EraseRegions.after.mir
-// fn main() -> (){
-//     let mut _0: ();
-//     scope 1 {
-//         scope 3 {
-//         }
-//         scope 4 {
-//             let _2: &ReErased Test;
-//         }
-//     }
-//     scope 2 {
-//         let _1: Test;
-//     }
-//     let mut _3: ();
-//     let mut _4: &ReErased i32;
-//     let mut _5: &ReErased i32;
-//     bb0: {
-//         StorageLive(_1);
-//         _1 = Test { x: const 0i32 };
-//         StorageLive(_2);
-//         Validate(Suspend(ReScope(Remainder { block: ItemLocalId(24), first_statement_index: 3 })), [_1: Test]);
-//         _2 = &ReErased _1;
-//         Validate(Acquire, [(*_2): Test/ReScope(Remainder { block: ItemLocalId(24), first_statement_index: 3 }) (imm)]);
-//         StorageLive(_4);
-//         StorageLive(_5);
-//         Validate(Suspend(ReScope(Node(ItemLocalId(22)))), [((*_2).0: i32): i32/ReScope(Remainder { block: ItemLocalId(24), first_statement_index: 3 }) (imm)]);
-//         _5 = &ReErased ((*_2).0: i32);
-//         Validate(Acquire, [(*_5): i32/ReScope(Node(ItemLocalId(22))) (imm)]);
-//         Validate(Suspend(ReScope(Node(ItemLocalId(22)))), [(*_5): i32/ReScope(Node(ItemLocalId(22))) (imm)]);
-//         _4 = &ReErased (*_5);
-//         Validate(Acquire, [(*_4): i32/ReScope(Node(ItemLocalId(22))) (imm)]);
-//         Validate(Release, [_3: (), _4: &ReScope(Node(ItemLocalId(22))) i32]);
-//         _3 = const foo(move _4) -> bb1;
-//     }
-//     bb1: {
-//         Validate(Acquire, [_3: ()]);
-//         EndRegion(ReScope(Node(ItemLocalId(22))));
-//         StorageDead(_4);
-//         StorageDead(_5);
-//         _0 = ();
-//         EndRegion(ReScope(Remainder { block: ItemLocalId(24), first_statement_index: 3 }));
-//         StorageDead(_2);
-//         StorageDead(_1);
-//         return;
-//     }
-// }
-// END rustc.main.EraseRegions.after.mir
diff --git a/src/test/mir-opt/validate_4.rs b/src/test/mir-opt/validate_4.rs
deleted file mode 100644
index 542ac8a4241..00000000000
--- a/src/test/mir-opt/validate_4.rs
+++ /dev/null
@@ -1,90 +0,0 @@
-// 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.
-
-// ignore-tidy-linelength
-// compile-flags: -Z verbose -Z mir-emit-validate=1 -Z span_free_formats
-
-// Make sure unsafe fns and fns with an unsafe block only get restricted validation.
-
-unsafe fn write_42(x: *mut i32) -> bool {
-    let test_closure = |x: *mut i32| *x = 23;
-    test_closure(x);
-    *x = 42;
-    true
-}
-
-fn test(x: &mut i32) {
-    unsafe { write_42(x) };
-}
-
-fn main() {
-    test(&mut 0);
-
-    let test_closure = unsafe { |x: &mut i32| write_42(x) };
-    test_closure(&mut 0);
-}
-
-// FIXME: Also test code generated inside the closure, make sure it only does restricted validation
-// because it is entirely inside an unsafe block.  Unfortunately, the interesting lines of code also
-// contain name of the source file, so we cannot test for it.
-
-// END RUST SOURCE
-// START rustc.write_42.EraseRegions.after.mir
-// fn write_42(_1: *mut i32) -> bool {
-//     ...
-//     bb0: {
-//         Validate(Acquire, [_1: *mut i32]);
-//         Validate(Release, [_1: *mut i32]);
-//         ...
-//         return;
-//     }
-// }
-// END rustc.write_42.EraseRegions.after.mir
-// START rustc.write_42-{{closure}}.EraseRegions.after.mir
-// fn write_42::{{closure}}(_1: &ReErased [closure@NodeId(32)], _2: *mut i32) -> () {
-//     ...
-//     bb0: {
-//         Validate(Acquire, [_1: &ReFree(DefId(0/1:9 ~ validate_4[317d]::write_42[0]::{{closure}}[0]), BrEnv) [closure@NodeId(32)], _2: *mut i32]);
-//         Validate(Release, [_1: &ReFree(DefId(0/1:9 ~ validate_4[317d]::write_42[0]::{{closure}}[0]), BrEnv) [closure@NodeId(32)], _2: *mut i32]);
-//         (*_2) = const 23i32;
-//         _0 = ();
-//         return;
-//     }
-// }
-// END rustc.write_42-{{closure}}.EraseRegions.after.mir
-// START rustc.test.EraseRegions.after.mir
-// fn test(_1: &ReErased mut i32) -> () {
-//     ...
-//     bb0: {
-//         Validate(Acquire, [_1: &ReFree(DefId(0/0:4 ~ validate_4[317d]::test[0]), BrAnon(0)) mut i32]);
-//         Validate(Release, [_1: &ReFree(DefId(0/0:4 ~ validate_4[317d]::test[0]), BrAnon(0)) mut i32]);
-//         ...
-//         _2 = const write_42(move _3) -> bb1;
-//     }
-//     bb1: {
-//         Validate(Acquire, [_2: bool]);
-//         Validate(Release, [_2: bool]);
-//         ...
-//     }
-// }
-// END rustc.test.EraseRegions.after.mir
-// START rustc.main-{{closure}}.EraseRegions.after.mir
-// fn main::{{closure}}(_1: &ReErased [closure@NodeId(80)], _2: &ReErased mut i32) -> bool {
-//     ...
-//     bb0: {
-//         Validate(Acquire, [_1: &ReFree(DefId(0/1:10 ~ validate_4[317d]::main[0]::{{closure}}[0]), BrEnv) [closure@NodeId(80)], _2: &ReFree(DefId(0/1:10 ~ validate_4[317d]::main[0]::{{closure}}[0]), BrAnon(0)) mut i32]);
-//         Validate(Release, [_1: &ReFree(DefId(0/1:10 ~ validate_4[317d]::main[0]::{{closure}}[0]), BrEnv) [closure@NodeId(80)], _2: &ReFree(DefId(0/1:10 ~ validate_4[317d]::main[0]::{{closure}}[0]), BrAnon(0)) mut i32]);
-//         StorageLive(_3);
-//         ...
-//         _0 = const write_42(move _3) -> bb1;
-//     }
-//     ...
-// }
-// END rustc.main-{{closure}}.EraseRegions.after.mir
diff --git a/src/test/mir-opt/validate_5.rs b/src/test/mir-opt/validate_5.rs
deleted file mode 100644
index 955de0c3bad..00000000000
--- a/src/test/mir-opt/validate_5.rs
+++ /dev/null
@@ -1,69 +0,0 @@
-// 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.
-
-// ignore-tidy-linelength
-// compile-flags: -Z verbose -Z mir-emit-validate=2 -Z span_free_formats
-
-// Make sure unsafe fns and fns with an unsafe block still get full validation.
-
-unsafe fn write_42(x: *mut i32) -> bool {
-    *x = 42;
-    true
-}
-
-fn test(x: &mut i32) {
-    unsafe { write_42(x) };
-}
-
-fn main() {
-    test(&mut 0);
-
-    let test_closure = unsafe { |x: &mut i32| write_42(x) };
-    // Note that validation will fail if this is executed: The closure keeps the lock on
-    // x, so the write in write_42 fails.  This test just checks code generation,
-    // so the UB doesn't matter.
-    test_closure(&mut 0);
-}
-
-// END RUST SOURCE
-// START rustc.test.EraseRegions.after.mir
-// fn test(_1: &ReErased mut i32) -> () {
-//     ...
-//     bb0: {
-//         Validate(Acquire, [_1: &ReFree(DefId(0/0:4 ~ validate_5[317d]::test[0]), BrAnon(0)) mut i32]);
-//         ...
-//         Validate(Release, [_2: bool, _3: *mut i32]);
-//         _2 = const write_42(move _3) -> bb1;
-//     }
-//     ...
-// }
-// END rustc.test.EraseRegions.after.mir
-// START rustc.main-{{closure}}.EraseRegions.after.mir
-// fn main::{{closure}}(_1: &ReErased [closure@NodeId(62)], _2: &ReErased mut i32) -> bool {
-//     ...
-//     bb0: {
-//         Validate(Acquire, [_1: &ReFree(DefId(0/1:9 ~ validate_5[317d]::main[0]::{{closure}}[0]), BrEnv) [closure@NodeId(62)], _2: &ReFree(DefId(0/1:9 ~ validate_5[317d]::main[0]::{{closure}}[0]), BrAnon(0)) mut i32]);
-//         StorageLive(_3);
-//         StorageLive(_4);
-//         StorageLive(_5);
-//         Validate(Suspend(ReScope(Node(ItemLocalId(16)))), [(*_2): i32]);
-//         _5 = &ReErased mut (*_2);
-//         Validate(Acquire, [(*_5): i32/ReScope(Node(ItemLocalId(16)))]);
-//         _4 = move _5 as *mut i32 (Misc);
-//         _3 = move _4;
-//         EndRegion(ReScope(Node(ItemLocalId(16))));
-//         StorageDead(_4);
-//         StorageDead(_5);
-//         Validate(Release, [_0: bool, _3: *mut i32]);
-//         _0 = const write_42(move _3) -> bb1;
-//     }
-//     ...
-// }
-// END rustc.main-{{closure}}.EraseRegions.after.mir