Auto merge of #112834 - oli-obk:mir_opts_considered_unsound, r=cjgillot

Disable two mir opts that are known to be unsound

closes #112460 (does not fix the underlying issue)

r? `@cjgillot`

compiler/rustc_mir_transform/src/const_goto.rs

@@ -28,7 +28,9 @@
 
 impl<'tcx> MirPass<'tcx> for ConstGoto {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
-        sess.mir_opt_level() >= 2
+        // This pass participates in some as-of-yet untested unsoundness found
+        // in https://github.com/rust-lang/rust/issues/112460
+        sess.mir_opt_level() >= 2 && sess.opts.unstable_opts.unsound_mir_opts
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {

compiler/rustc_mir_transform/src/separate_const_switch.rs

@@ -46,7 +46,9 @@
 
 impl<'tcx> MirPass<'tcx> for SeparateConstSwitch {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
-        sess.mir_opt_level() >= 2
+        // This pass participates in some as-of-yet untested unsoundness found
+        // in https://github.com/rust-lang/rust/issues/112460
+        sess.mir_opt_level() >= 2 && sess.opts.unstable_opts.unsound_mir_opts
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {

tests/mir-opt/const_goto_const_eval_fail.rs

@@ -1,6 +1,8 @@
 #![feature(min_const_generics)]
 #![crate_type = "lib"]
 
+// compile-flags: -Zunsound-mir-opts
+
 // If const eval fails, then don't crash
 // EMIT_MIR const_goto_const_eval_fail.f.ConstGoto.diff
 pub fn f<const A: i32, const B: bool>() -> u64 {

tests/mir-opt/pre-codegen/chained_comparison.naive.PreCodegen.after.mir

@@ -7,26 +7,26 @@ fn naive(_1: &Blueprint, _2: &Blueprint) -> bool {
     let mut _3: u32;
     let mut _4: u32;
     let mut _5: bool;
-    let mut _6: u32;
+    let mut _6: bool;
     let mut _7: u32;
-    let mut _8: bool;
+    let mut _8: u32;
     let mut _9: bool;
-    let mut _10: u32;
+    let mut _10: bool;
     let mut _11: u32;
-    let mut _12: bool;
+    let mut _12: u32;
     let mut _13: bool;
-    let mut _14: u32;
+    let mut _14: bool;
     let mut _15: u32;
-    let mut _16: bool;
+    let mut _16: u32;
     let mut _17: bool;
     let mut _18: u32;
     let mut _19: u32;
     let mut _20: bool;
 
     bb0: {
-        StorageLive(_17);
+        StorageLive(_14);
-        StorageLive(_13);
+        StorageLive(_10);
-        StorageLive(_9);
+        StorageLive(_6);
         StorageLive(_5);
         StorageLive(_3);
         _3 = ((*_1).0: u32);
@@ -39,74 +39,83 @@ fn naive(_1: &Blueprint, _2: &Blueprint) -> bool {
     }
 
     bb1: {
-        StorageDead(_8);
+        _6 = const false;
-        StorageDead(_5);
         goto -> bb3;
     }
 
     bb2: {
-        StorageLive(_8);
+        StorageLive(_9);
-        StorageLive(_6);
-        _6 = ((*_1).1: u32);
         StorageLive(_7);
-        _7 = ((*_2).1: u32);
+        _7 = ((*_1).1: u32);
-        _8 = Eq(move _6, move _7);
+        StorageLive(_8);
-        StorageDead(_7);
+        _8 = ((*_2).1: u32);
-        StorageDead(_6);
+        _9 = Eq(move _7, move _8);
-        _9 = move _8;
         StorageDead(_8);
-        StorageDead(_5);
+        StorageDead(_7);
-        switchInt(move _9) -> [0: bb3, otherwise: bb4];
+        _6 = move _9;
+        goto -> bb3;
     }
 
     bb3: {
-        StorageDead(_12);
         StorageDead(_9);
-        goto -> bb5;
+        StorageDead(_5);
+        switchInt(move _6) -> [0: bb4, otherwise: bb5];
     }
 
     bb4: {
-        StorageLive(_12);
+        _10 = const false;
-        StorageLive(_10);
+        goto -> bb6;
-        _10 = ((*_1).2: u32);
-        StorageLive(_11);
-        _11 = ((*_2).2: u32);
-        _12 = Eq(move _10, move _11);
-        StorageDead(_11);
-        StorageDead(_10);
-        _13 = move _12;
-        StorageDead(_12);
-        StorageDead(_9);
-        switchInt(move _13) -> [0: bb5, otherwise: bb6];
     }
 
     bb5: {
-        StorageDead(_16);
+        StorageLive(_13);
-        StorageDead(_13);
+        StorageLive(_11);
-        goto -> bb7;
+        _11 = ((*_1).2: u32);
+        StorageLive(_12);
+        _12 = ((*_2).2: u32);
+        _13 = Eq(move _11, move _12);
+        StorageDead(_12);
+        StorageDead(_11);
+        _10 = move _13;
+        goto -> bb6;
     }
 
     bb6: {
-        StorageLive(_16);
-        StorageLive(_14);
-        _14 = ((*_1).3: u32);
-        StorageLive(_15);
-        _15 = ((*_2).3: u32);
-        _16 = Eq(move _14, move _15);
-        StorageDead(_15);
-        StorageDead(_14);
-        _17 = move _16;
-        StorageDead(_16);
         StorageDead(_13);
-        switchInt(move _17) -> [0: bb7, otherwise: bb8];
+        StorageDead(_6);
+        switchInt(move _10) -> [0: bb7, otherwise: bb8];
     }
 
     bb7: {
-        _0 = const false;
+        _14 = const false;
         goto -> bb9;
     }
 
     bb8: {
+        StorageLive(_17);
+        StorageLive(_15);
+        _15 = ((*_1).3: u32);
+        StorageLive(_16);
+        _16 = ((*_2).3: u32);
+        _17 = Eq(move _15, move _16);
+        StorageDead(_16);
+        StorageDead(_15);
+        _14 = move _17;
+        goto -> bb9;
+    }
+
+    bb9: {
+        StorageDead(_17);
+        StorageDead(_10);
+        switchInt(move _14) -> [0: bb10, otherwise: bb11];
+    }
+
+    bb10: {
+        _0 = const false;
+        goto -> bb12;
+    }
+
+    bb11: {
         StorageLive(_20);
         StorageLive(_18);
         _18 = ((*_1).4: u32);
@@ -116,12 +125,12 @@ fn naive(_1: &Blueprint, _2: &Blueprint) -> bool {
         StorageDead(_19);
         StorageDead(_18);
         _0 = move _20;
-        goto -> bb9;
+        goto -> bb12;
     }
 
-    bb9: {
+    bb12: {
         StorageDead(_20);
-        StorageDead(_17);
+        StorageDead(_14);
         return;
     }
 }

tests/mir-opt/pre-codegen/slice_filter.variant_a-{closure#0}.PreCodegen.after.mir

@@ -14,10 +14,10 @@ fn variant_a::{closure#0}(_1: &mut [closure@$DIR/slice_filter.rs:7:25: 7:39], _2
     let _12: &usize;
     let mut _13: &&usize;
     let mut _18: bool;
-    let mut _19: &&usize;
+    let mut _19: bool;
-    let _20: &usize;
+    let mut _20: &&usize;
-    let mut _21: &&usize;
+    let _21: &usize;
-    let mut _26: bool;
+    let mut _22: &&usize;
     let mut _27: bool;
     let mut _28: &&usize;
     let _29: &usize;
@@ -58,15 +58,15 @@ fn variant_a::{closure#0}(_1: &mut [closure@$DIR/slice_filter.rs:7:25: 7:39], _2
             }
         }
         scope 6 (inlined cmp::impls::<impl PartialOrd for &usize>::le) {
-            debug self => _19;
+            debug self => _20;
-            debug other => _21;
+            debug other => _22;
-            let mut _22: &usize;
             let mut _23: &usize;
+            let mut _24: &usize;
             scope 7 (inlined cmp::impls::<impl PartialOrd for usize>::le) {
-                debug self => _22;
+                debug self => _23;
-                debug other => _23;
+                debug other => _24;
-                let mut _24: usize;
                 let mut _25: usize;
+                let mut _26: usize;
             }
         }
         scope 8 (inlined cmp::impls::<impl PartialOrd for &usize>::le) {
@@ -96,7 +96,7 @@ fn variant_a::{closure#0}(_1: &mut [closure@$DIR/slice_filter.rs:7:25: 7:39], _2
         StorageLive(_10);
         _9 = deref_copy (*_2);
         _10 = &((*_9).3: usize);
-        StorageLive(_27);
+        StorageLive(_19);
         StorageLive(_18);
         StorageLive(_11);
         _11 = &_4;
@@ -120,38 +120,41 @@ fn variant_a::{closure#0}(_1: &mut [closure@$DIR/slice_filter.rs:7:25: 7:39], _2
     }
 
     bb1: {
-        StorageDead(_26);
+        _19 = const false;
-        StorageDead(_18);
         goto -> bb3;
     }
 
     bb2: {
-        StorageLive(_26);
+        StorageLive(_27);
-        StorageLive(_19);
-        _19 = &_10;
-        StorageLive(_21);
         StorageLive(_20);
-        _20 = _6;
+        _20 = &_10;
-        _21 = &_20;
+        StorageLive(_22);
-        _22 = deref_copy (*_19);
+        StorageLive(_21);
-        _23 = deref_copy (*_21);
+        _21 = _6;
-        StorageLive(_24);
+        _22 = &_21;
-        _24 = (*_22);
+        _23 = deref_copy (*_20);
+        _24 = deref_copy (*_22);
         StorageLive(_25);
         _25 = (*_23);
-        _26 = Le(move _24, move _25);
+        StorageLive(_26);
-        StorageDead(_25);
+        _26 = (*_24);
-        StorageDead(_24);
+        _27 = Le(move _25, move _26);
-        StorageDead(_20);
-        StorageDead(_21);
-        StorageDead(_19);
-        _27 = move _26;
         StorageDead(_26);
-        StorageDead(_18);
+        StorageDead(_25);
-        switchInt(move _27) -> [0: bb3, otherwise: bb7];
+        StorageDead(_21);
+        StorageDead(_22);
+        StorageDead(_20);
+        _19 = move _27;
+        goto -> bb3;
     }
 
     bb3: {
+        StorageDead(_27);
+        StorageDead(_18);
+        switchInt(move _19) -> [0: bb4, otherwise: bb8];
+    }
+
+    bb4: {
         StorageLive(_36);
         StorageLive(_35);
         StorageLive(_28);
@@ -172,15 +175,15 @@ fn variant_a::{closure#0}(_1: &mut [closure@$DIR/slice_filter.rs:7:25: 7:39], _2
         StorageDead(_29);
         StorageDead(_30);
         StorageDead(_28);
-        switchInt(move _35) -> [0: bb4, otherwise: bb5];
+        switchInt(move _35) -> [0: bb5, otherwise: bb6];
-    }
-
-    bb4: {
-        _36 = const false;
-        goto -> bb6;
     }
 
     bb5: {
+        _36 = const false;
+        goto -> bb7;
+    }
+
+    bb6: {
         StorageLive(_44);
         StorageLive(_37);
         _37 = &_6;
@@ -201,24 +204,24 @@ fn variant_a::{closure#0}(_1: &mut [closure@$DIR/slice_filter.rs:7:25: 7:39], _2
         StorageDead(_39);
         StorageDead(_37);
         _36 = move _44;
-        goto -> bb6;
+        goto -> bb7;
-    }
-
-    bb6: {
-        StorageDead(_44);
-        StorageDead(_35);
-        _0 = move _36;
-        goto -> bb8;
     }
 
     bb7: {
-        _0 = const true;
+        StorageDead(_44);
-        goto -> bb8;
+        StorageDead(_35);
+        _0 = move _36;
+        goto -> bb9;
     }
 
     bb8: {
+        _0 = const true;
+        goto -> bb9;
+    }
+
+    bb9: {
         StorageDead(_36);
-        StorageDead(_27);
+        StorageDead(_19);
         StorageDead(_10);
         StorageDead(_8);
         StorageDead(_6);

tests/mir-opt/pre-codegen/slice_filter.variant_b-{closure#0}.PreCodegen.after.mir

@@ -32,61 +32,64 @@ fn variant_b::{closure#0}(_1: &mut [closure@$DIR/slice_filter.rs:11:25: 11:41],
         _8 = ((*_7).2: usize);
         _9 = deref_copy (*_2);
         _10 = ((*_9).3: usize);
-        StorageLive(_13);
+        StorageLive(_12);
         StorageLive(_11);
         _11 = Le(_4, _8);
         switchInt(move _11) -> [0: bb1, otherwise: bb2];
     }
 
     bb1: {
-        StorageDead(_12);
+        _12 = const false;
-        StorageDead(_11);
         goto -> bb3;
     }
 
     bb2: {
-        StorageLive(_12);
+        StorageLive(_13);
-        _12 = Le(_10, _6);
+        _13 = Le(_10, _6);
-        _13 = move _12;
+        _12 = move _13;
-        StorageDead(_12);
+        goto -> bb3;
-        StorageDead(_11);
-        switchInt(move _13) -> [0: bb3, otherwise: bb7];
     }
 
     bb3: {
-        StorageLive(_15);
+        StorageDead(_13);
-        StorageLive(_14);
+        StorageDead(_11);
-        _14 = Le(_8, _4);
+        switchInt(move _12) -> [0: bb4, otherwise: bb8];
-        switchInt(move _14) -> [0: bb4, otherwise: bb5];
     }
 
     bb4: {
-        _15 = const false;
+        StorageLive(_15);
-        goto -> bb6;
+        StorageLive(_14);
+        _14 = Le(_8, _4);
+        switchInt(move _14) -> [0: bb5, otherwise: bb6];
     }
 
     bb5: {
-        StorageLive(_16);
+        _15 = const false;
-        _16 = Le(_6, _10);
+        goto -> bb7;
-        _15 = move _16;
-        goto -> bb6;
     }
 
     bb6: {
-        StorageDead(_16);
+        StorageLive(_16);
-        StorageDead(_14);
+        _16 = Le(_6, _10);
-        _0 = move _15;
+        _15 = move _16;
-        goto -> bb8;
+        goto -> bb7;
     }
 
     bb7: {
-        _0 = const true;
+        StorageDead(_16);
-        goto -> bb8;
+        StorageDead(_14);
+        _0 = move _15;
+        goto -> bb9;
     }
 
     bb8: {
+        _0 = const true;
+        goto -> bb9;
+    }
+
+    bb9: {
         StorageDead(_15);
-        StorageDead(_13);
+        StorageDead(_12);
         return;
     }
 }

tests/mir-opt/pre-codegen/slice_index.slice_get_unchecked_mut_range.PreCodegen.after.panic-abort.mir

@@ -17,50 +17,37 @@ fn slice_get_unchecked_mut_range(_1: &mut [u32], _2: std::ops::Range<usize>) ->
                 debug slice => _5;
                 let mut _7: *mut u32;
                 let mut _8: *mut u32;
+                let _14: usize;
                 let _15: usize;
-                let _16: usize;
                 scope 4 {
-                    debug this => std::ops::Range<usize>{ .0 => _15, .1 => _16, };
+                    debug this => std::ops::Range<usize>{ .0 => _14, .1 => _15, };
                     scope 5 {
                         let _6: usize;
                         scope 6 {
                             debug new_len => _6;
-                            scope 11 (inlined ptr::mut_ptr::<impl *mut [u32]>::as_mut_ptr) {
+                            scope 7 (inlined ptr::mut_ptr::<impl *mut [u32]>::as_mut_ptr) {
                                 debug self => _5;
                             }
-                            scope 12 (inlined ptr::mut_ptr::<impl *mut u32>::add) {
+                            scope 8 (inlined ptr::mut_ptr::<impl *mut u32>::add) {
                                 debug self => _7;
                                 debug count => _3;
-                                scope 13 {
+                                scope 9 {
                                 }
                             }
-                            scope 14 (inlined slice_from_raw_parts_mut::<u32>) {
+                            scope 10 (inlined slice_from_raw_parts_mut::<u32>) {
                                 debug data => _8;
                                 debug len => _6;
                                 let mut _9: *mut ();
-                                scope 15 (inlined ptr::mut_ptr::<impl *mut u32>::cast::<()>) {
+                                scope 11 (inlined ptr::mut_ptr::<impl *mut u32>::cast::<()>) {
                                     debug self => _8;
                                 }
-                                scope 16 (inlined std::ptr::from_raw_parts_mut::<[u32]>) {
+                                scope 12 (inlined std::ptr::from_raw_parts_mut::<[u32]>) {
                                     debug data_address => _9;
                                     debug metadata => _6;
                                     let mut _10: *const ();
                                     let mut _11: std::ptr::metadata::PtrComponents<[u32]>;
                                     let mut _12: std::ptr::metadata::PtrRepr<[u32]>;
-                                    scope 17 {
+                                    scope 13 {
-                                    }
-                                }
-                            }
-                        }
-                        scope 7 (inlined <std::ops::Range<usize> as SliceIndex<[T]>>::get_unchecked_mut::runtime::<u32>) {
-                            debug this => std::ops::Range<usize>{ .0 => _15, .1 => _16, };
-                            debug slice => _5;
-                            scope 8 (inlined ptr::mut_ptr::<impl *mut [u32]>::len) {
-                                debug self => _5;
-                                let mut _14: *const [u32];
-                                scope 9 (inlined std::ptr::metadata::<[u32]>) {
-                                    debug ptr => _14;
-                                    scope 10 {
                                     }
                                 }
                             }
@@ -77,10 +64,9 @@ fn slice_get_unchecked_mut_range(_1: &mut [u32], _2: std::ops::Range<usize>) ->
         StorageLive(_13);
         StorageLive(_5);
         _5 = &raw mut (*_1);
-        StorageLive(_6);
         StorageLive(_14);
         StorageLive(_15);
-        StorageLive(_16);
+        StorageLive(_6);
         _6 = SubUnchecked(_4, _3);
         StorageLive(_8);
         StorageLive(_7);
@@ -101,10 +87,9 @@ fn slice_get_unchecked_mut_range(_1: &mut [u32], _2: std::ops::Range<usize>) ->
         StorageDead(_12);
         StorageDead(_9);
         StorageDead(_8);
-        StorageDead(_16);
-        StorageDead(_15);
-        StorageDead(_14);
         StorageDead(_6);
+        StorageDead(_14);
+        StorageDead(_15);
         StorageDead(_5);
         _0 = &mut (*_13);
         StorageDead(_13);

tests/mir-opt/pre-codegen/slice_index.slice_get_unchecked_mut_range.PreCodegen.after.panic-unwind.mir

@@ -17,50 +17,37 @@ fn slice_get_unchecked_mut_range(_1: &mut [u32], _2: std::ops::Range<usize>) ->
                 debug slice => _5;
                 let mut _7: *mut u32;
                 let mut _8: *mut u32;
+                let _14: usize;
                 let _15: usize;
-                let _16: usize;
                 scope 4 {
-                    debug this => std::ops::Range<usize>{ .0 => _15, .1 => _16, };
+                    debug this => std::ops::Range<usize>{ .0 => _14, .1 => _15, };
                     scope 5 {
                         let _6: usize;
                         scope 6 {
                             debug new_len => _6;
-                            scope 11 (inlined ptr::mut_ptr::<impl *mut [u32]>::as_mut_ptr) {
+                            scope 7 (inlined ptr::mut_ptr::<impl *mut [u32]>::as_mut_ptr) {
                                 debug self => _5;
                             }
-                            scope 12 (inlined ptr::mut_ptr::<impl *mut u32>::add) {
+                            scope 8 (inlined ptr::mut_ptr::<impl *mut u32>::add) {
                                 debug self => _7;
                                 debug count => _3;
-                                scope 13 {
+                                scope 9 {
                                 }
                             }
-                            scope 14 (inlined slice_from_raw_parts_mut::<u32>) {
+                            scope 10 (inlined slice_from_raw_parts_mut::<u32>) {
                                 debug data => _8;
                                 debug len => _6;
                                 let mut _9: *mut ();
-                                scope 15 (inlined ptr::mut_ptr::<impl *mut u32>::cast::<()>) {
+                                scope 11 (inlined ptr::mut_ptr::<impl *mut u32>::cast::<()>) {
                                     debug self => _8;
                                 }
-                                scope 16 (inlined std::ptr::from_raw_parts_mut::<[u32]>) {
+                                scope 12 (inlined std::ptr::from_raw_parts_mut::<[u32]>) {
                                     debug data_address => _9;
                                     debug metadata => _6;
                                     let mut _10: *const ();
                                     let mut _11: std::ptr::metadata::PtrComponents<[u32]>;
                                     let mut _12: std::ptr::metadata::PtrRepr<[u32]>;
-                                    scope 17 {
+                                    scope 13 {
-                                    }
-                                }
-                            }
-                        }
-                        scope 7 (inlined <std::ops::Range<usize> as SliceIndex<[T]>>::get_unchecked_mut::runtime::<u32>) {
-                            debug this => std::ops::Range<usize>{ .0 => _15, .1 => _16, };
-                            debug slice => _5;
-                            scope 8 (inlined ptr::mut_ptr::<impl *mut [u32]>::len) {
-                                debug self => _5;
-                                let mut _14: *const [u32];
-                                scope 9 (inlined std::ptr::metadata::<[u32]>) {
-                                    debug ptr => _14;
-                                    scope 10 {
                                     }
                                 }
                             }
@@ -77,10 +64,9 @@ fn slice_get_unchecked_mut_range(_1: &mut [u32], _2: std::ops::Range<usize>) ->
         StorageLive(_13);
         StorageLive(_5);
         _5 = &raw mut (*_1);
-        StorageLive(_6);
         StorageLive(_14);
         StorageLive(_15);
-        StorageLive(_16);
+        StorageLive(_6);
         _6 = SubUnchecked(_4, _3);
         StorageLive(_8);
         StorageLive(_7);
@@ -101,10 +87,9 @@ fn slice_get_unchecked_mut_range(_1: &mut [u32], _2: std::ops::Range<usize>) ->
         StorageDead(_12);
         StorageDead(_9);
         StorageDead(_8);
-        StorageDead(_16);
-        StorageDead(_15);
-        StorageDead(_14);
         StorageDead(_6);
+        StorageDead(_14);
+        StorageDead(_15);
         StorageDead(_5);
         _0 = &mut (*_13);
         StorageDead(_13);

tests/mir-opt/separate_const_switch.rs

@@ -1,6 +1,8 @@
 #![feature(control_flow_enum)]
 #![feature(try_trait_v2)]
 
+// compile-flags: -Zunsound-mir-opts
+
 use std::ops::ControlFlow;
 
 // EMIT_MIR separate_const_switch.too_complex.SeparateConstSwitch.diff