Auto merge of #124156 - DianQK:disable-match_branches, r=<try>

Disable MatchBranchSimplification Due to the miscompilation mentioned in #124150, We need to disable MatchBranchSimplification temporarily. To fully resolve this issue, my plan is: 1. Disable MatchBranchSimplification (this PR). 2. Remove all potentially unclear transforms in #124122. 3. Gradually add back the removed transforms (possibly multiple PRs). r? `@Nilstrieb` or `@oli-obk`
rust-lang · Apr 19, 2024 · e7a5d6f · e7a5d6f
2 parents c4f112a + 2d3178b
commit e7a5d6f
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Showing 11 changed files with 154 additions and 71 deletions.
diff --git a/compiler/rustc_mir_transform/src/match_branches.rs b/compiler/rustc_mir_transform/src/match_branches.rs
@@ -11,7 +11,8 @@ pub struct MatchBranchSimplification;
 
 impl<'tcx> MirPass<'tcx> for MatchBranchSimplification {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
-        sess.mir_opt_level() >= 1
+        // unsound: https://github.com/rust-lang/rust/issues/124150
+        sess.mir_opt_level() >= 1 && sess.opts.unstable_opts.unsound_mir_opts
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {

diff --git a/...pt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-unwind.diff b/...pt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-unwind.diff
@@ -19,11 +19,11 @@
                   let _6: *mut [bool; 0];
                   scope 6 {
                       scope 10 (inlined NonNull::<[bool; 0]>::new_unchecked) {
-                          let mut _8: bool;
-                          let _9: ();
-                          let mut _10: *mut ();
-                          let mut _11: *const [bool; 0];
+                          let _8: ();
+                          let mut _9: *mut ();
+                          let mut _10: *const [bool; 0];
                           scope 11 (inlined core::ub_checks::check_language_ub) {
+                              let mut _11: bool;
                               scope 12 (inlined core::ub_checks::check_language_ub::runtime) {
                               }
                           }
@@ -44,18 +44,18 @@
           StorageLive(_1);
           StorageLive(_2);
           StorageLive(_3);
-          StorageLive(_9);
+          StorageLive(_8);
           StorageLive(_4);
           StorageLive(_5);
           StorageLive(_6);
           StorageLive(_7);
           _7 = const 1_usize;
           _6 = const {0x1 as *mut [bool; 0]};
           StorageDead(_7);
+          StorageLive(_10);
           StorageLive(_11);
-          StorageLive(_8);
-          _8 = UbChecks();
-          switchInt(move _8) -> [0: bb5, otherwise: bb3];
+          _11 = UbChecks();
+          switchInt(move _11) -> [0: bb6, otherwise: bb5];
       }
 
       bb1: {
@@ -68,34 +68,39 @@
       }
 
       bb3: {
-          StorageLive(_10);
-          _10 = const {0x1 as *mut ()};
-          _9 = NonNull::<T>::new_unchecked::precondition_check(const {0x1 as *mut ()}) -> [return: bb4, unwind unreachable];
+          StorageDead(_9);
+          goto -> bb4;
       }
 
       bb4: {
-          StorageDead(_10);
-          goto -> bb5;
-      }
-
-      bb5: {
-          StorageDead(_8);
-          _11 = const {0x1 as *const [bool; 0]};
+          _10 = const {0x1 as *const [bool; 0]};
           _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
-          StorageDead(_11);
+          StorageDead(_10);
           StorageDead(_6);
           _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
           StorageDead(_5);
           _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC0, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
           StorageDead(_4);
           _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC1, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
-          StorageDead(_9);
+          StorageDead(_8);
           StorageDead(_3);
           _1 = const A {{ foo: Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC2, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) }};
           StorageDead(_2);
           _0 = const ();
           drop(_1) -> [return: bb1, unwind: bb2];
       }
+
+      bb5: {
+          StorageDead(_11);
+          StorageLive(_9);
+          _9 = const {0x1 as *mut ()};
+          _8 = NonNull::<T>::new_unchecked::precondition_check(const {0x1 as *mut ()}) -> [return: bb3, unwind unreachable];
+      }
+
+      bb6: {
+          StorageDead(_11);
+          goto -> bb4;
+      }
   }
 
   ALLOC2 (size: 16, align: 8) {

diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-unwind.diff
@@ -19,11 +19,11 @@
                   let _6: *mut [bool; 0];
                   scope 6 {
                       scope 10 (inlined NonNull::<[bool; 0]>::new_unchecked) {
-                          let mut _8: bool;
-                          let _9: ();
-                          let mut _10: *mut ();
-                          let mut _11: *const [bool; 0];
+                          let _8: ();
+                          let mut _9: *mut ();
+                          let mut _10: *const [bool; 0];
                           scope 11 (inlined core::ub_checks::check_language_ub) {
+                              let mut _11: bool;
                               scope 12 (inlined core::ub_checks::check_language_ub::runtime) {
                               }
                           }
@@ -44,7 +44,7 @@
           StorageLive(_1);
           StorageLive(_2);
           StorageLive(_3);
-          StorageLive(_9);
+          StorageLive(_8);
           StorageLive(_4);
           StorageLive(_5);
           StorageLive(_6);
@@ -54,10 +54,10 @@
 +         _7 = const 1_usize;
 +         _6 = const {0x1 as *mut [bool; 0]};
           StorageDead(_7);
+          StorageLive(_10);
           StorageLive(_11);
-          StorageLive(_8);
-          _8 = UbChecks();
-          switchInt(move _8) -> [0: bb5, otherwise: bb3];
+          _11 = UbChecks();
+          switchInt(move _11) -> [0: bb6, otherwise: bb5];
       }
 
       bb1: {
@@ -70,25 +70,16 @@
       }
 
       bb3: {
-          StorageLive(_10);
--         _10 = _6 as *mut () (PtrToPtr);
--         _9 = NonNull::<T>::new_unchecked::precondition_check(move _10) -> [return: bb4, unwind unreachable];
-+         _10 = const {0x1 as *mut ()};
-+         _9 = NonNull::<T>::new_unchecked::precondition_check(const {0x1 as *mut ()}) -> [return: bb4, unwind unreachable];
+          StorageDead(_9);
+          goto -> bb4;
       }
 
       bb4: {
-          StorageDead(_10);
-          goto -> bb5;
-      }
-
-      bb5: {
-          StorageDead(_8);
--         _11 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
--         _5 = NonNull::<[bool; 0]> { pointer: _11 };
-+         _11 = const {0x1 as *const [bool; 0]};
+-         _10 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
+-         _5 = NonNull::<[bool; 0]> { pointer: _10 };
++         _10 = const {0x1 as *const [bool; 0]};
 +         _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
-          StorageDead(_11);
+          StorageDead(_10);
           StorageDead(_6);
 -         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
 +         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
@@ -98,14 +89,28 @@
           StorageDead(_4);
 -         _2 = Box::<[bool]>(_3, const std::alloc::Global);
 +         _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC1, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
-          StorageDead(_9);
+          StorageDead(_8);
           StorageDead(_3);
 -         _1 = A { foo: move _2 };
 +         _1 = const A {{ foo: Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC2, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) }};
           StorageDead(_2);
           _0 = const ();
           drop(_1) -> [return: bb1, unwind: bb2];
       }
+
+      bb5: {
+          StorageDead(_11);
+          StorageLive(_9);
+-         _9 = _6 as *mut () (PtrToPtr);
+-         _8 = NonNull::<T>::new_unchecked::precondition_check(move _9) -> [return: bb3, unwind unreachable];
++         _9 = const {0x1 as *mut ()};
++         _8 = NonNull::<T>::new_unchecked::precondition_check(const {0x1 as *mut ()}) -> [return: bb3, unwind unreachable];
+      }
+
+      bb6: {
+          StorageDead(_11);
+          goto -> bb4;
+      }
 + }
 + 
 + ALLOC2 (size: 16, align: 8) {

diff --git a/tests/mir-opt/inline/unwrap_unchecked.unwrap_unchecked.Inline.panic-unwind.diff b/tests/mir-opt/inline/unwrap_unchecked.unwrap_unchecked.Inline.panic-unwind.diff
@@ -12,7 +12,9 @@
 +         scope 3 (inlined unreachable_unchecked) {
 +             let mut _4: bool;
 +             let _5: ();
++             let mut _7: bool;
 +             scope 4 (inlined core::ub_checks::check_language_ub) {
++                 let mut _6: bool;
 +                 scope 5 (inlined core::ub_checks::check_language_ub::runtime) {
 +                 }
 +             }
@@ -30,26 +32,42 @@
       }
 
       bb1: {
--         StorageDead(_2);
--         return;
 +         unreachable;
-      }
-
--     bb2 (cleanup): {
--         resume;
++     }
++ 
 +     bb2: {
++         StorageLive(_7);
 +         StorageLive(_4);
-+         _4 = UbChecks();
-+         assume(_4);
-+         _5 = unreachable_unchecked::precondition_check() -> [return: bb1, unwind unreachable];
++         StorageLive(_6);
++         _6 = UbChecks();
++         switchInt(move _6) -> [0: bb5, otherwise: bb4];
 +     }
 + 
 +     bb3: {
 +         _0 = move ((_2 as Some).0: T);
 +         StorageDead(_5);
 +         StorageDead(_3);
-+         StorageDead(_2);
-+         return;
+          StorageDead(_2);
+          return;
+      }
+
+-     bb2 (cleanup): {
+-         resume;
++     bb4: {
++         _4 = const true;
++         goto -> bb6;
++     }
++ 
++     bb5: {
++         _4 = const false;
++         goto -> bb6;
++     }
++ 
++     bb6: {
++         StorageDead(_6);
++         _7 = _4;
++         assume(move _7);
++         _5 = unreachable_unchecked::precondition_check() -> [return: bb1, unwind unreachable];
       }
   }
 
diff --git a/tests/mir-opt/inline/unwrap_unchecked.unwrap_unchecked.PreCodegen.after.panic-unwind.mir b/tests/mir-opt/inline/unwrap_unchecked.unwrap_unchecked.PreCodegen.after.panic-unwind.mir
@@ -8,6 +8,8 @@ fn unwrap_unchecked(_1: Option<T>) -> T {
         scope 2 {
         }
         scope 3 (inlined unreachable_unchecked) {
+            let mut _3: bool;
+            let _4: ();
             scope 4 (inlined core::ub_checks::check_language_ub) {
                 scope 5 (inlined core::ub_checks::check_language_ub::runtime) {
                 }
@@ -18,16 +20,22 @@ fn unwrap_unchecked(_1: Option<T>) -> T {
     bb0: {
         StorageLive(_2);
         _2 = discriminant(_1);
-        switchInt(move _2) -> [0: bb2, 1: bb1, otherwise: bb2];
+        switchInt(move _2) -> [0: bb1, 1: bb2, otherwise: bb3];
     }
 
     bb1: {
+        _3 = const false;
+        assume(_3);
+        _4 = unreachable_unchecked::precondition_check() -> [return: bb3, unwind unreachable];
+    }
+
+    bb2: {
         _0 = ((_1 as Some).0: T);
         StorageDead(_2);
         return;
     }
 
-    bb2: {
+    bb3: {
         unreachable;
     }
 }
diff --git a/tests/mir-opt/instsimplify/ub_check.rs b/tests/mir-opt/instsimplify/ub_check.rs
@@ -1,4 +1,5 @@
 //@ unit-test: InstSimplify
+//@ should-fail Broken due to https://github.com/rust-lang/rust/issues/124150.
 //@ compile-flags: -Cdebug-assertions=no -Zinline-mir
 
 // EMIT_MIR ub_check.unwrap_unchecked.InstSimplify.diff

diff --git a/tests/mir-opt/instsimplify/ub_check.unwrap_unchecked.InstSimplify.diff b/tests/mir-opt/instsimplify/ub_check.unwrap_unchecked.InstSimplify.diff
@@ -12,7 +12,9 @@
           scope 3 (inlined unreachable_unchecked) {
               let mut _4: bool;
               let _5: ();
+              let mut _7: bool;
               scope 4 (inlined core::ub_checks::check_language_ub) {
+                  let mut _6: bool;
                   scope 5 (inlined core::ub_checks::check_language_ub::runtime) {
                   }
               }
@@ -33,11 +35,12 @@
       }
 
       bb2: {
+          StorageLive(_7);
           StorageLive(_4);
--         _4 = UbChecks();
-+         _4 = const false;
-          assume(_4);
-          _5 = unreachable_unchecked::precondition_check() -> [return: bb1, unwind unreachable];
+          StorageLive(_6);
+-         _6 = UbChecks();
++         _6 = const false;
+          switchInt(move _6) -> [0: bb5, otherwise: bb4];
       }
 
       bb3: {
@@ -47,5 +50,22 @@
           StorageDead(_2);
           return;
       }
+
+      bb4: {
+          _4 = const true;
+          goto -> bb6;
+      }
+
+      bb5: {
+          _4 = const false;
+          goto -> bb6;
+      }
+
+      bb6: {
+          StorageDead(_6);
+          _7 = _4;
+          assume(move _7);
+          _5 = unreachable_unchecked::precondition_check() -> [return: bb1, unwind unreachable];
+      }
   }
 
diff --git a/tests/mir-opt/issues/issue_75439.rs b/tests/mir-opt/issues/issue_75439.rs
@@ -1,9 +1,10 @@
+//@ unit-test: MatchBranchSimplification
 // skip-filecheck
-// EMIT_MIR issue_75439.foo.MatchBranchSimplification.diff
 //@ ignore-endian-big
 
 use std::mem::transmute;
 
+// EMIT_MIR issue_75439.foo.MatchBranchSimplification.diff
 pub fn foo(bytes: [u8; 16]) -> Option<[u8; 4]> {
     // big endian `u32`s
     let dwords: [u32; 4] = unsafe { transmute(bytes) };

diff --git a/tests/mir-opt/pre-codegen/duplicate_switch_targets.ub_if_b.PreCodegen.after.mir b/tests/mir-opt/pre-codegen/duplicate_switch_targets.ub_if_b.PreCodegen.after.mir
@@ -5,6 +5,8 @@ fn ub_if_b(_1: Thing) -> Thing {
     let mut _0: Thing;
     let mut _2: isize;
     scope 1 (inlined unreachable_unchecked) {
+        let mut _3: bool;
+        let _4: ();
         scope 2 (inlined core::ub_checks::check_language_ub) {
             scope 3 (inlined core::ub_checks::check_language_ub::runtime) {
             }
@@ -13,7 +15,7 @@ fn ub_if_b(_1: Thing) -> Thing {
 
     bb0: {
         _2 = discriminant(_1);
-        switchInt(move _2) -> [0: bb1, 1: bb2, otherwise: bb2];
+        switchInt(move _2) -> [0: bb1, 1: bb2, otherwise: bb3];
     }
 
     bb1: {
@@ -22,6 +24,12 @@ fn ub_if_b(_1: Thing) -> Thing {
     }
 
     bb2: {
+        _3 = const false;
+        assume(_3);
+        _4 = unreachable_unchecked::precondition_check() -> [return: bb3, unwind unreachable];
+    }
+
+    bb3: {
         unreachable;
     }
 }