Add test checking that fallthrough branches are correctly identified as dead

6 files changed, 128 insertions, 17 deletions

diff --git a/src/test/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff b/src/test/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff
index 6d149b89edb..79b923a2889 100644
--- a/src/test/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff
+++ b/src/test/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff
@@ -31,7 +31,7 @@
           StorageDead(_5);                 // scope 0 at $DIR/early_otherwise_branch.rs:12:16: 12:17
           StorageDead(_4);                 // scope 0 at $DIR/early_otherwise_branch.rs:12:16: 12:17
           _8 = discriminant((_3.0: std::option::Option<u32>)); // scope 0 at $DIR/early_otherwise_branch.rs:12:11: 12:17
--         switchInt(move _8) -> [0_isize: bb1, 1_isize: bb3, otherwise: bb2]; // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
+-         switchInt(move _8) -> [0_isize: bb1, 1_isize: bb3, otherwise: bb7]; // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
 +         StorageLive(_11);                // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
 +         _11 = discriminant((_3.1: std::option::Option<u32>)); // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
 +         StorageLive(_12);                // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
@@ -81,8 +81,10 @@
 +     bb4: {
           StorageDead(_3);                 // scope 0 at $DIR/early_otherwise_branch.rs:17:1: 17:2
           return;                          // scope 0 at $DIR/early_otherwise_branch.rs:17:2: 17:2
-+     }
-+ 
+      }
+  
+-     bb7: {
+-         unreachable;                     // scope 0 at $DIR/early_otherwise_branch.rs:15:14: 15:15
 +     bb5: {
 +         StorageDead(_12);                // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
 +         switchInt(_8) -> [0_isize: bb3, 1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
diff --git a/src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.before-SimplifyConstCondition-final.after.diff b/src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.before-SimplifyConstCondition-final.after.diff
index fc2dcb25109..db6794db298 100644
--- a/src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.before-SimplifyConstCondition-final.after.diff
+++ b/src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.before-SimplifyConstCondition-final.after.diff
@@ -81,7 +81,7 @@
 -         StorageDead(_5);                 // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:23: 21:24
 +         nop;                             // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:23: 21:24
           _11 = discriminant((*(_4.0: &ViewportPercentageLength))); // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:14: 21:24
--         switchInt(move _11) -> [0_isize: bb1, 1_isize: bb3, 2_isize: bb4, 3_isize: bb5, otherwise: bb2]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
+-         switchInt(move _11) -> [0_isize: bb1, 1_isize: bb3, 2_isize: bb4, 3_isize: bb5, otherwise: bb11]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
 +         StorageLive(_34);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
 +         _34 = discriminant((*(_4.1: &ViewportPercentageLength))); // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
 +         StorageLive(_35);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
@@ -217,14 +217,9 @@
 -         StorageDead(_13);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:49: 22:50
 -         StorageDead(_12);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:49: 22:50
 -         goto -> bb10;                    // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:49: 22:50
-+         nop;                             // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:5: 27:7
-+         discriminant(_0) = 0;            // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:5: 27:7
-+         nop;                             // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:6: 27:7
-+         nop;                             // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:1: 28:2
-+         return;                          // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:2: 28:2
-      }
-  
-      bb7: {
+-     }
+- 
+-     bb7: {
 -         StorageLive(_17);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:14: 23:17
 -         _17 = (((*(_4.0: &ViewportPercentageLength)) as Vh).0: f32); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:14: 23:17
 -         StorageLive(_18);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:24: 23:29
@@ -289,10 +284,18 @@
 - 
 -     bb10: {
 -         ((_0 as Ok).0: ViewportPercentageLength) = move _3; // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:5: 27:7
--         discriminant(_0) = 0;            // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:5: 27:7
++         nop;                             // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:5: 27:7
+          discriminant(_0) = 0;            // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:5: 27:7
 -         StorageDead(_3);                 // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:6: 27:7
 -         StorageDead(_4);                 // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:1: 28:2
--         return;                          // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:2: 28:2
++         nop;                             // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:6: 27:7
++         nop;                             // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:1: 28:2
+          return;                          // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:2: 28:2
+      }
+  
+-     bb11: {
+-         unreachable;                     // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:2: 28:2
++     bb7: {
 +         StorageDead(_35);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
 +         switchInt(_11) -> [0_isize: bb2, 1_isize: bb3, 2_isize: bb4, 3_isize: bb5, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
       }
diff --git a/src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.diff b/src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.diff
index 28c650d72dc..c8d8ae7766d 100644
--- a/src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.diff
+++ b/src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.diff
@@ -67,7 +67,7 @@
           StorageDead(_6);                 // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:23: 21:24
           StorageDead(_5);                 // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:23: 21:24
           _11 = discriminant((*(_4.0: &ViewportPercentageLength))); // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:14: 21:24
--         switchInt(move _11) -> [0_isize: bb1, 1_isize: bb3, 2_isize: bb4, 3_isize: bb5, otherwise: bb2]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
+-         switchInt(move _11) -> [0_isize: bb1, 1_isize: bb3, 2_isize: bb4, 3_isize: bb5, otherwise: bb11]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
 +         StorageLive(_34);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
 +         _34 = discriminant((*(_4.1: &ViewportPercentageLength))); // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
 +         StorageLive(_35);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
@@ -206,8 +206,10 @@
           StorageDead(_3);                 // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:6: 27:7
           StorageDead(_4);                 // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:1: 28:2
           return;                          // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:2: 28:2
-+     }
-+ 
+      }
+  
+-     bb11: {
+-         unreachable;                     // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:2: 28:2
 +     bb7: {
 +         StorageDead(_35);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
 +         switchInt(_11) -> [0_isize: bb2, 1_isize: bb3, 2_isize: bb4, 3_isize: bb5, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:21:8: 21:24
diff --git a/src/test/mir-opt/uninhabited_fallthrough_elimination.eliminate_fallthrough.UninhabitedEnumBranching.diff b/src/test/mir-opt/uninhabited_fallthrough_elimination.eliminate_fallthrough.UninhabitedEnumBranching.diff
new file mode 100644
index 00000000000..7e843b65e88
--- /dev/null
+++ b/src/test/mir-opt/uninhabited_fallthrough_elimination.eliminate_fallthrough.UninhabitedEnumBranching.diff
@@ -0,0 +1,38 @@
+- // MIR for `eliminate_fallthrough` before UninhabitedEnumBranching
++ // MIR for `eliminate_fallthrough` after UninhabitedEnumBranching
+  
+  fn eliminate_fallthrough(_1: S) -> u32 {
+      debug s => _1;                       // in scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:21:26: 21:27
+      let mut _0: u32;                     // return place in scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:21:35: 21:38
+      let mut _2: isize;                   // in scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:23:9: 23:10
+  
+      bb0: {
+          _2 = discriminant(_1);           // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:22:11: 22:12
+-         switchInt(move _2) -> [1_isize: bb3, 2_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:22:5: 22:12
++         switchInt(move _2) -> [1_isize: bb3, 2_isize: bb2, otherwise: bb5]; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:22:5: 22:12
+      }
+  
+      bb1: {
+          _0 = const 3_u32;                // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:25:14: 25:15
+          goto -> bb4;                     // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:25:14: 25:15
+      }
+  
+      bb2: {
+          _0 = const 1_u32;                // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:23:14: 23:15
+          goto -> bb4;                     // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:23:14: 23:15
+      }
+  
+      bb3: {
+          _0 = const 2_u32;                // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:24:14: 24:15
+          goto -> bb4;                     // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:24:14: 24:15
+      }
+  
+      bb4: {
+          return;                          // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:27:2: 27:2
++     }
++ 
++     bb5: {
++         unreachable;                     // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:25:14: 25:15
+      }
+  }
+  
diff --git a/src/test/mir-opt/uninhabited_fallthrough_elimination.keep_fallthrough.UninhabitedEnumBranching.diff b/src/test/mir-opt/uninhabited_fallthrough_elimination.keep_fallthrough.UninhabitedEnumBranching.diff
new file mode 100644
index 00000000000..5da011d427a
--- /dev/null
+++ b/src/test/mir-opt/uninhabited_fallthrough_elimination.keep_fallthrough.UninhabitedEnumBranching.diff
@@ -0,0 +1,34 @@
+- // MIR for `keep_fallthrough` before UninhabitedEnumBranching
++ // MIR for `keep_fallthrough` after UninhabitedEnumBranching
+  
+  fn keep_fallthrough(_1: S) -> u32 {
+      debug s => _1;                       // in scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:12:21: 12:22
+      let mut _0: u32;                     // return place in scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:12:30: 12:33
+      let mut _2: isize;                   // in scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:14:9: 14:13
+  
+      bb0: {
+          _2 = discriminant(_1);           // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:13:11: 13:12
+-         switchInt(move _2) -> [0_isize: bb2, 1_isize: bb3, otherwise: bb1]; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:13:5: 13:12
++         switchInt(move _2) -> [1_isize: bb3, otherwise: bb1]; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:13:5: 13:12
+      }
+  
+      bb1: {
+          _0 = const 3_u32;                // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:16:14: 16:15
+          goto -> bb4;                     // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:16:14: 16:15
+      }
+  
+      bb2: {
+          _0 = const 1_u32;                // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:14:17: 14:18
+          goto -> bb4;                     // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:14:17: 14:18
+      }
+  
+      bb3: {
+          _0 = const 2_u32;                // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:15:14: 15:15
+          goto -> bb4;                     // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:15:14: 15:15
+      }
+  
+      bb4: {
+          return;                          // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:18:2: 18:2
+      }
+  }
+  
diff --git a/src/test/mir-opt/uninhabited_fallthrough_elimination.rs b/src/test/mir-opt/uninhabited_fallthrough_elimination.rs
new file mode 100644
index 00000000000..0853883f8b8
--- /dev/null
+++ b/src/test/mir-opt/uninhabited_fallthrough_elimination.rs
@@ -0,0 +1,32 @@
+enum Empty {}
+
+enum S {
+    A(Empty),
+    B,
+    C,
+}
+
+use S::*;
+
+// EMIT_MIR uninhabited_fallthrough_elimination.keep_fallthrough.UninhabitedEnumBranching.diff
+fn keep_fallthrough(s: S) -> u32 {
+    match s {
+        A(_) => 1,
+        B => 2,
+        _ => 3,
+    }
+}
+
+// EMIT_MIR uninhabited_fallthrough_elimination.eliminate_fallthrough.UninhabitedEnumBranching.diff
+fn eliminate_fallthrough(s: S) -> u32 {
+    match s {
+        C => 1,
+        B => 2,
+        _ => 3,
+    }
+}
+
+fn main() {
+    keep_fallthrough(B);
+    eliminate_fallthrough(B);
+}