Don't modify the otherwise of the switch

Author: dianqk

compiler/rustc_mir_transform/src/early_otherwise_branch.rs

@@ -166,7 +166,8 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
                 };
                 (value, targets.all_targets()[0])
             });
-            let eq_targets = SwitchTargets::new(eq_new_targets, opt_data.destination);
+
+            let eq_targets = SwitchTargets::new(eq_new_targets, parent_targets.otherwise());
 
             // Create `bbEq` in example above
             let eq_switch = BasicBlockData::new(Some(Terminator {

tests/mir-opt/early_otherwise_branch.opt10.EarlyOtherwiseBranch.diff

@@ -27,7 +27,7 @@
 -         switchInt(move _9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb9];
 +         StorageLive(_10);
 +         _10 = discriminant((_3.1: E16));
-+         switchInt(move _10) -> [0: bb6, otherwise: bb1];
++         switchInt(move _10) -> [0: bb7, otherwise: bb1];
       }
 
       bb1: {
@@ -40,49 +40,51 @@
       bb2: {
 -         _6 = discriminant((_3.1: E16));
 -         switchInt(move _6) -> [0: bb5, otherwise: bb1];
--     }
-- 
--     bb3: {
++         _0 = const 1_u32;
++         goto -> bb5;
+      }
+  
+      bb3: {
 -         _7 = discriminant((_3.1: E16));
 -         switchInt(move _7) -> [0: bb6, otherwise: bb1];
--     }
-- 
--     bb4: {
++         _0 = const 2_u32;
++         goto -> bb5;
+      }
+  
+      bb4: {
 -         _8 = discriminant((_3.1: E16));
 -         switchInt(move _8) -> [0: bb7, otherwise: bb1];
--     }
-- 
--     bb5: {
-          _0 = const 1_u32;
--         goto -> bb8;
++         _0 = const 3_u32;
 +         goto -> bb5;
       }
 
--     bb6: {
-+     bb3: {
-          _0 = const 2_u32;
+      bb5: {
+-         _0 = const 1_u32;
 -         goto -> bb8;
-+         goto -> bb5;
++         StorageDead(_3);
++         return;
       }
 
--     bb7: {
-+     bb4: {
-          _0 = const 3_u32;
+      bb6: {
+-         _0 = const 2_u32;
 -         goto -> bb8;
-+         goto -> bb5;
++         unreachable;
       }
 
+      bb7: {
+-         _0 = const 3_u32;
+-         goto -> bb8;
+-     }
+- 
 -     bb8: {
-+     bb5: {
-          StorageDead(_3);
-          return;
-      }
-  
+-         StorageDead(_3);
+-         return;
+-     }
+- 
 -     bb9: {
 -         unreachable;
-+     bb6: {
 +         StorageDead(_10);
-+         switchInt(_9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb1];
++         switchInt(_9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb6];
       }
   }
 

tests/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff

@@ -36,7 +36,7 @@
 +         StorageLive(_12);
 +         _12 = Ne(_8, move _11);
 +         StorageDead(_11);
-+         switchInt(move _12) -> [0: bb5, otherwise: bb1];
++         switchInt(move _12) -> [0: bb6, otherwise: bb1];
       }
 
       bb1: {
@@ -82,10 +82,13 @@
       }
 
 -     bb7: {
--         unreachable;
 +     bb5: {
+          unreachable;
++     }
++ 
++     bb6: {
 +         StorageDead(_12);
-+         switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb1];
++         switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb5];
       }
   }
 

tests/mir-opt/early_otherwise_branch.opt3.EarlyOtherwiseBranch.diff

@@ -36,7 +36,7 @@
 +         StorageLive(_12);
 +         _12 = Ne(_8, move _11);
 +         StorageDead(_11);
-+         switchInt(move _12) -> [0: bb5, otherwise: bb1];
++         switchInt(move _12) -> [0: bb6, otherwise: bb1];
       }
 
       bb1: {
@@ -82,10 +82,13 @@
       }
 
 -     bb7: {
--         unreachable;
 +     bb5: {
+          unreachable;
++     }
++ 
++     bb6: {
 +         StorageDead(_12);
-+         switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb1];
++         switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb5];
       }
   }
 

tests/mir-opt/early_otherwise_branch.opt7.EarlyOtherwiseBranch.diff

@@ -36,7 +36,7 @@
 -         switchInt(move _8) -> [0: bb2, 1: bb3, otherwise: bb7];
 +         StorageLive(_12);
 +         _12 = discriminant((_3.1: std::option::Option<u32>));
-+         switchInt(move _12) -> [1: bb5, otherwise: bb1];
++         switchInt(move _12) -> [1: bb6, otherwise: bb1];
       }
 
       bb1: {
@@ -85,10 +85,13 @@
       }
 
 -     bb7: {
--         unreachable;
 +     bb5: {
+          unreachable;
++     }
++ 
++     bb6: {
 +         StorageDead(_12);
-+         switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb1];
++         switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb5];
       }
   }
 

tests/mir-opt/early_otherwise_branch.rs

@@ -170,10 +170,13 @@ fn opt10(x: E8, y: E16) -> u32 {
     // CHECK: bb0: {
     // CHECK: [[LOCAL1:_.*]] = discriminant({{.*}});
     // CHECK: [[LOCAL2:_.*]] = discriminant({{.*}});
-    // CHECK: switchInt(move [[LOCAL2]]) -> [0: [[SWITCH_BB:bb.*]], otherwise: [[OTHERWISE:bb.*]]];
+    // CHECK: switchInt(move [[LOCAL2]]) -> [0: [[SWITCH_BB:bb.*]], otherwise: {{bb.*}}];
+    // CHECK-NEXT: }
+    // CHECK: [[UNREACHABLE:bb6]]: {
+    // CHECK-NEXT: unreachable;
     // CHECK-NEXT: }
     // CHECK: [[SWITCH_BB]]:
-    // CHECK:  switchInt([[LOCAL1]]) -> [0: bb{{.*}}, 1: bb{{.*}}, 2: bb{{.*}}, otherwise: [[OTHERWISE]]];
+    // CHECK:  switchInt([[LOCAL1]]) -> [0: bb{{.*}}, 1: bb{{.*}}, 2: bb{{.*}}, otherwise: [[UNREACHABLE]]];
     // CHECK-NEXT: }
     match (x, y) {
         (E8::A, E16::A) => 1,

tests/mir-opt/early_otherwise_branch_3_element_tuple.opt1.EarlyOtherwiseBranch.diff

@@ -45,7 +45,7 @@
 +         StorageLive(_17);
 +         _17 = Ne(_12, move _16);
 +         StorageDead(_16);
-+         switchInt(move _17) -> [0: bb7, otherwise: bb1];
++         switchInt(move _17) -> [0: bb8, otherwise: bb1];
       }
 
       bb1: {
@@ -108,10 +108,13 @@
       }
 
 -     bb9: {
--         unreachable;
 +     bb7: {
+          unreachable;
++     }
++ 
++     bb8: {
 +         StorageDead(_17);
-+         switchInt(_12) -> [0: bb2, 1: bb3, otherwise: bb1];
++         switchInt(_12) -> [0: bb2, 1: bb3, otherwise: bb7];
       }
   }