[mir-opt] Disable the `ConsideredEqual` logic in SimplifyBranchSame opt

The logic is currently broken and we need to disable it to fix a beta
regression (see #76803)

2 files changed, 31 insertions, 15 deletions

diff --git a/src/test/mir-opt/simplify_arm.id.SimplifyBranchSame.diff b/src/test/mir-opt/simplify_arm.id.SimplifyBranchSame.diff
index 81a0e6ba0b4..06f359da2e7 100644
--- a/src/test/mir-opt/simplify_arm.id.SimplifyBranchSame.diff
+++ b/src/test/mir-opt/simplify_arm.id.SimplifyBranchSame.diff
@@ -13,27 +13,24 @@
   
       bb0: {
           _2 = discriminant(_1);           // scope 0 at $DIR/simplify-arm.rs:11:9: 11:16
--         switchInt(move _2) -> [0_isize: bb1, 1_isize: bb3, otherwise: bb2]; // scope 0 at $DIR/simplify-arm.rs:11:9: 11:16
-+         goto -> bb1;                     // scope 0 at $DIR/simplify-arm.rs:11:9: 11:16
+          switchInt(move _2) -> [0_isize: bb1, 1_isize: bb3, otherwise: bb2]; // scope 0 at $DIR/simplify-arm.rs:11:9: 11:16
       }
   
       bb1: {
--         discriminant(_0) = 0;            // scope 0 at $DIR/simplify-arm.rs:12:17: 12:21
--         goto -> bb4;                     // scope 0 at $DIR/simplify-arm.rs:10:5: 13:6
--     }
-- 
--     bb2: {
--         unreachable;                     // scope 0 at $DIR/simplify-arm.rs:10:11: 10:12
--     }
-- 
--     bb3: {
+          discriminant(_0) = 0;            // scope 0 at $DIR/simplify-arm.rs:12:17: 12:21
+          goto -> bb4;                     // scope 0 at $DIR/simplify-arm.rs:10:5: 13:6
+      }
+  
+      bb2: {
+          unreachable;                     // scope 0 at $DIR/simplify-arm.rs:10:11: 10:12
+      }
+  
+      bb3: {
           _0 = move _1;                    // scope 1 at $DIR/simplify-arm.rs:11:20: 11:27
--         goto -> bb4;                     // scope 0 at $DIR/simplify-arm.rs:10:5: 13:6
-+         goto -> bb2;                     // scope 0 at $DIR/simplify-arm.rs:10:5: 13:6
+          goto -> bb4;                     // scope 0 at $DIR/simplify-arm.rs:10:5: 13:6
       }
   
--     bb4: {
-+     bb2: {
+      bb4: {
           return;                          // scope 0 at $DIR/simplify-arm.rs:14:2: 14:2
       }
   }
diff --git a/src/test/ui/mir/issue-76803-branches-not-same.rs b/src/test/ui/mir/issue-76803-branches-not-same.rs
new file mode 100644
index 00000000000..a6a57622005
--- /dev/null
+++ b/src/test/ui/mir/issue-76803-branches-not-same.rs
@@ -0,0 +1,19 @@
+// run-pass
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum Type {
+    A,
+    B,
+}
+
+
+pub fn encode(v: Type) -> Type {
+    match v {
+        Type::A => Type::B,
+        _ => v,
+    }
+}
+
+fn main() {
+  assert_eq!(Type::B, encode(Type::A));
+}