Only emit != assumptions if the otherwise target is reachable.

cjgillot · cjgillot · commit 9ad64b98bb6b · 2023-10-18T18:28:53.000Z
diff --git a/compiler/rustc_mir_transform/src/unreachable_prop.rs b/compiler/rustc_mir_transform/src/unreachable_prop.rs
@@ -116,22 +116,21 @@ fn remove_successors_from_switch<'tcx>(
         patch.add_statement(location, StatementKind::Intrinsic(Box::new(assume)));
     };
 
+    let otherwise = targets.otherwise();
+    let otherwise_unreachable = is_unreachable(otherwise);
+
     let reachable_iter = targets.iter().filter(|&(value, bb)| {
         let is_unreachable = is_unreachable(bb);
-        if is_unreachable {
-            // We remove this target from the switch, so record the inequality using `Assume`.
+        // We remove this target from the switch, so record the inequality using `Assume`.
+        if is_unreachable && !otherwise_unreachable {
             add_assumption(BinOp::Ne, value);
-            false
-        } else {
-            true
         }
+        !is_unreachable
     });
 
-    let otherwise = targets.otherwise();
     let new_targets = SwitchTargets::new(reachable_iter, otherwise);
 
     let num_targets = new_targets.all_targets().len();
-    let otherwise_unreachable = is_unreachable(otherwise);
     let fully_unreachable = num_targets == 1 && otherwise_unreachable;
 
     let terminator = match (num_targets, otherwise_unreachable) {
diff --git a/tests/mir-opt/inline/unwrap_unchecked.unwrap_unchecked.Inline.panic-abort.diff b/tests/mir-opt/inline/unwrap_unchecked.unwrap_unchecked.Inline.panic-abort.diff
@@ -10,7 +10,6 @@
 +         let mut _3: &std::option::Option<T>;
 +         let mut _4: isize;
 +         let mut _5: bool;
-+         let mut _6: bool;
 +         scope 2 {
 +             debug val => _0;
 +         }
@@ -37,14 +36,10 @@
 +         StorageLive(_3);
 +         StorageLive(_4);
 +         StorageLive(_5);
-+         StorageLive(_6);
 +         _4 = discriminant(_2);
-+         _5 = Ne(_4, const 0_isize);
++         _5 = Eq(_4, const 1_isize);
 +         assume(move _5);
-+         _6 = Eq(_4, const 1_isize);
-+         assume(move _6);
 +         _0 = move ((_2 as Some).0: T);
-+         StorageDead(_6);
 +         StorageDead(_5);
 +         StorageDead(_4);
 +         StorageDead(_3);
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
@@ -10,7 +10,6 @@
 +         let mut _3: &std::option::Option<T>;
 +         let mut _4: isize;
 +         let mut _5: bool;
-+         let mut _6: bool;
 +         scope 2 {
 +             debug val => _0;
 +         }
@@ -37,14 +36,10 @@
 +         StorageLive(_3);
 +         StorageLive(_4);
 +         StorageLive(_5);
-+         StorageLive(_6);
 +         _4 = discriminant(_2);
-+         _5 = Ne(_4, const 0_isize);
++         _5 = Eq(_4, const 1_isize);
 +         assume(move _5);
-+         _6 = Eq(_4, const 1_isize);
-+         assume(move _6);
 +         _0 = move ((_2 as Some).0: T);
-+         StorageDead(_6);
 +         StorageDead(_5);
 +         StorageDead(_4);
 +         StorageDead(_3);
diff --git a/tests/mir-opt/inline/unwrap_unchecked.unwrap_unchecked.PreCodegen.after.panic-abort.mir b/tests/mir-opt/inline/unwrap_unchecked.unwrap_unchecked.PreCodegen.after.panic-abort.mir
@@ -7,8 +7,7 @@ fn unwrap_unchecked(_1: Option<T>) -> T {
         debug self => _1;
         let mut _2: isize;
         let mut _3: bool;
-        let mut _4: bool;
-        let mut _5: &std::option::Option<T>;
+        let mut _4: &std::option::Option<T>;
         scope 2 {
             debug val => _0;
         }
@@ -21,25 +20,21 @@ fn unwrap_unchecked(_1: Option<T>) -> T {
             }
         }
         scope 4 (inlined Option::<T>::is_some) {
-            debug self => _5;
+            debug self => _4;
         }
     }
 
     bb0: {
-        StorageLive(_5);
-        StorageLive(_3);
         StorageLive(_4);
         StorageLive(_2);
+        StorageLive(_3);
         _2 = discriminant(_1);
-        _3 = Ne(_2, const 0_isize);
+        _3 = Eq(_2, const 1_isize);
         assume(move _3);
-        _4 = Eq(_2, const 1_isize);
-        assume(move _4);
         _0 = move ((_1 as Some).0: T);
+        StorageDead(_3);
         StorageDead(_2);
         StorageDead(_4);
-        StorageDead(_3);
-        StorageDead(_5);
         return;
     }
 }
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
@@ -7,8 +7,7 @@ fn unwrap_unchecked(_1: Option<T>) -> T {
         debug self => _1;
         let mut _2: isize;
         let mut _3: bool;
-        let mut _4: bool;
-        let mut _5: &std::option::Option<T>;
+        let mut _4: &std::option::Option<T>;
         scope 2 {
             debug val => _0;
         }
@@ -21,25 +20,21 @@ fn unwrap_unchecked(_1: Option<T>) -> T {
             }
         }
         scope 4 (inlined Option::<T>::is_some) {
-            debug self => _5;
+            debug self => _4;
         }
     }
 
     bb0: {
-        StorageLive(_5);
-        StorageLive(_3);
         StorageLive(_4);
         StorageLive(_2);
+        StorageLive(_3);
         _2 = discriminant(_1);
-        _3 = Ne(_2, const 0_isize);
+        _3 = Eq(_2, const 1_isize);
         assume(move _3);
-        _4 = Eq(_2, const 1_isize);
-        assume(move _4);
         _0 = move ((_1 as Some).0: T);
+        StorageDead(_3);
         StorageDead(_2);
         StorageDead(_4);
-        StorageDead(_3);
-        StorageDead(_5);
         return;
     }
 }
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
@@ -5,7 +5,6 @@ fn ub_if_b(_1: Thing) -> Thing {
     let mut _0: Thing;
     let mut _2: isize;
     let mut _3: bool;
-    let mut _4: bool;
     scope 1 (inlined unreachable_unchecked) {
         scope 2 {
             scope 3 (inlined unreachable_unchecked::runtime) {
@@ -15,10 +14,8 @@ fn ub_if_b(_1: Thing) -> Thing {
 
     bb0: {
         _2 = discriminant(_1);
-        _3 = Ne(_2, const 1_isize);
+        _3 = Eq(_2, const 0_isize);
         assume(move _3);
-        _4 = Eq(_2, const 0_isize);
-        assume(move _4);
         _0 = move _1;
         return;
     }
diff --git a/tests/mir-opt/uninhabited_enum_branching.main.SimplifyCfg-after-uninhabited-enum-branching.after.mir b/tests/mir-opt/uninhabited_enum_branching.main.SimplifyCfg-after-uninhabited-enum-branching.after.mir
@@ -12,20 +12,14 @@ fn main() -> () {
     let mut _8: isize;
     let _9: &str;
     let mut _10: bool;
-    let mut _11: bool;
-    let mut _12: bool;
 
     bb0: {
         StorageLive(_1);
         StorageLive(_2);
         _2 = Test1::C;
         _3 = discriminant(_2);
-        _10 = Ne(_3, const 0_isize);
+        _10 = Eq(_3, const 2_isize);
         assume(move _10);
-        _11 = Ne(_3, const 1_isize);
-        assume(move _11);
-        _12 = Eq(_3, const 2_isize);
-        assume(move _12);
         StorageLive(_5);
         _5 = const "C";
         _1 = &(*_5);
diff --git a/tests/mir-opt/uninhabited_enum_branching2.main.SimplifyCfg-after-uninhabited-enum-branching.after.mir b/tests/mir-opt/uninhabited_enum_branching2.main.SimplifyCfg-after-uninhabited-enum-branching.after.mir
@@ -15,10 +15,6 @@ fn main() -> () {
     let _11: &str;
     let _12: &str;
     let _13: &str;
-    let mut _14: bool;
-    let mut _15: bool;
-    let mut _16: bool;
-    let mut _17: bool;
     scope 1 {
         debug plop => _1;
     }
@@ -33,10 +29,6 @@ fn main() -> () {
         StorageLive(_4);
         _4 = &(_1.1: Test1);
         _5 = discriminant((*_4));
-        _16 = Ne(_5, const 0_isize);
-        assume(move _16);
-        _17 = Ne(_5, const 1_isize);
-        assume(move _17);
         switchInt(move _5) -> [2: bb3, 3: bb1, otherwise: bb2];
     }
 
@@ -65,10 +57,6 @@ fn main() -> () {
         StorageDead(_3);
         StorageLive(_9);
         _10 = discriminant((_1.1: Test1));
-        _14 = Ne(_10, const 0_isize);
-        assume(move _14);
-        _15 = Ne(_10, const 1_isize);
-        assume(move _15);
         switchInt(move _10) -> [2: bb6, 3: bb5, otherwise: bb2];
     }
 
diff --git a/tests/mir-opt/unreachable.main.UnreachablePropagation.panic-abort.diff b/tests/mir-opt/unreachable.main.UnreachablePropagation.panic-abort.diff
@@ -9,7 +9,6 @@
       let mut _6: bool;
       let mut _7: !;
 +     let mut _8: bool;
-+     let mut _9: bool;
       scope 1 {
           debug _x => _3;
           let _3: Empty;
@@ -27,8 +26,8 @@
       bb1: {
           _2 = discriminant(_1);
 -         switchInt(move _2) -> [1: bb2, otherwise: bb6];
-+         _9 = Ne(_2, const 1_isize);
-+         assume(move _9);
++         _8 = Ne(_2, const 1_isize);
++         assume(move _8);
 +         goto -> bb6;
       }
   
diff --git a/tests/mir-opt/unreachable.main.UnreachablePropagation.panic-unwind.diff b/tests/mir-opt/unreachable.main.UnreachablePropagation.panic-unwind.diff
@@ -9,7 +9,6 @@
       let mut _6: bool;
       let mut _7: !;
 +     let mut _8: bool;
-+     let mut _9: bool;
       scope 1 {
           debug _x => _3;
           let _3: Empty;
@@ -27,8 +26,8 @@
       bb1: {
           _2 = discriminant(_1);
 -         switchInt(move _2) -> [1: bb2, otherwise: bb6];
-+         _9 = Ne(_2, const 1_isize);
-+         assume(move _9);
++         _8 = Ne(_2, const 1_isize);
++         assume(move _8);
 +         goto -> bb6;
       }
   

Original file line number	Diff line number	Diff line change
`@@ -7,8 +7,7 @@ fn unwrap_unchecked(_1: Option<T>) -> T {`
`7`	`7`	`debug self => _1;`
`8`	`8`	`let mut _2: isize;`
`9`	`9`	`let mut _3: bool;`
`10`		`- let mut _4: bool;`
`11`		`- let mut _5: &std::option::Option<T>;`
	`10`	`+ let mut _4: &std::option::Option<T>;`
`12`	`11`	`scope 2 {`
`13`	`12`	`debug val => _0;`
`14`	`13`	`}`
`@@ -21,25 +20,21 @@ fn unwrap_unchecked(_1: Option<T>) -> T {`
`21`	`20`	`}`
`22`	`21`	`}`
`23`	`22`	`scope 4 (inlined Option::<T>::is_some) {`
`24`		`- debug self => _5;`
	`23`	`+ debug self => _4;`
`25`	`24`	`}`
`26`	`25`	`}`
`27`	`26`
`28`	`27`	`bb0: {`
`29`		`- StorageLive(_5);`
`30`		`- StorageLive(_3);`
`31`	`28`	`StorageLive(_4);`
`32`	`29`	`StorageLive(_2);`
	`30`	`+ StorageLive(_3);`
`33`	`31`	`_2 = discriminant(_1);`
`34`		`- _3 = Ne(_2, const 0_isize);`
	`32`	`+ _3 = Eq(_2, const 1_isize);`
`35`	`33`	`assume(move _3);`
`36`		`- _4 = Eq(_2, const 1_isize);`
`37`		`- assume(move _4);`
`38`	`34`	`_0 = move ((_1 as Some).0: T);`
	`35`	`+ StorageDead(_3);`
`39`	`36`	`StorageDead(_2);`
`40`	`37`	`StorageDead(_4);`
`41`		`- StorageDead(_3);`
`42`		`- StorageDead(_5);`
`43`	`38`	`return;`
`44`	`39`	`}`
`45`	`40`	`}`