Improve test coverage of early_otherwise_branch mir opt

src/test/mir-opt/early_otherwise_branch_soundness.no_deref_ptr.EarlyOtherwiseBranch.diff

@@ -0,0 +1,43 @@
+- // MIR for `no_deref_ptr` before EarlyOtherwiseBranch
++ // MIR for `no_deref_ptr` after EarlyOtherwiseBranch
+  
+  fn no_deref_ptr(_1: Option<i32>, _2: *const Option<i32>) -> i32 {
+      debug a => _1;                       // in scope 0 at $DIR/early_otherwise_branch_soundness.rs:18:24: 18:25
+      debug b => _2;                       // in scope 0 at $DIR/early_otherwise_branch_soundness.rs:18:40: 18:41
+      let mut _0: i32;                     // return place in scope 0 at $DIR/early_otherwise_branch_soundness.rs:18:66: 18:69
+      let mut _3: isize;                   // in scope 0 at $DIR/early_otherwise_branch_soundness.rs:21:9: 21:16
+      let mut _4: isize;                   // in scope 0 at $DIR/early_otherwise_branch_soundness.rs:22:13: 22:20
+      let _5: i32;                         // in scope 0 at $DIR/early_otherwise_branch_soundness.rs:22:18: 22:19
+      scope 1 {
+          debug v => _5;                   // in scope 1 at $DIR/early_otherwise_branch_soundness.rs:22:18: 22:19
+      }
+  
+      bb0: {
+          _3 = discriminant(_1);           // scope 0 at $DIR/early_otherwise_branch_soundness.rs:19:11: 19:12
+          switchInt(move _3) -> [1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_soundness.rs:19:5: 19:12
+      }
+  
+      bb1: {
+          _0 = const 0_i32;                // scope 0 at $DIR/early_otherwise_branch_soundness.rs:25:14: 25:15
+          return;                          // scope 0 at $DIR/early_otherwise_branch_soundness.rs:25:14: 25:15
+      }
+  
+      bb2: {
+          _4 = discriminant((*_2));        // scope 0 at $DIR/early_otherwise_branch_soundness.rs:21:26: 21:28
+          switchInt(move _4) -> [1_isize: bb4, otherwise: bb3]; // scope 0 at $DIR/early_otherwise_branch_soundness.rs:21:20: 21:28
+      }
+  
+      bb3: {
+          _0 = const 0_i32;                // scope 0 at $DIR/early_otherwise_branch_soundness.rs:23:18: 23:19
+          return;                          // scope 0 at $DIR/early_otherwise_branch_soundness.rs:23:18: 23:19
+      }
+  
+      bb4: {
+          StorageLive(_5);                 // scope 0 at $DIR/early_otherwise_branch_soundness.rs:22:18: 22:19
+          _5 = (((*_2) as Some).0: i32);   // scope 0 at $DIR/early_otherwise_branch_soundness.rs:22:18: 22:19
+          _0 = _5;                         // scope 1 at $DIR/early_otherwise_branch_soundness.rs:22:24: 22:25
+          StorageDead(_5);                 // scope 0 at $DIR/early_otherwise_branch_soundness.rs:22:24: 22:25
+          return;                          // scope 0 at $DIR/early_otherwise_branch_soundness.rs:22:24: 22:25
+      }
+  }
+  

src/test/mir-opt/early_otherwise_branch_soundness.no_downcast.EarlyOtherwiseBranch.diff

@@ -0,0 +1,30 @@
+- // MIR for `no_downcast` before EarlyOtherwiseBranch
++ // MIR for `no_downcast` after EarlyOtherwiseBranch
+  
+  fn no_downcast(_1: &E) -> u32 {
+      debug e => _1;                       // in scope 0 at $DIR/early_otherwise_branch_soundness.rs:12:16: 12:17
+      let mut _0: u32;                     // return place in scope 0 at $DIR/early_otherwise_branch_soundness.rs:12:26: 12:29
+      let mut _2: isize;                   // in scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:20: 13:30
+      let mut _3: isize;                   // in scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:12: 13:31
+  
+      bb0: {
+          _3 = discriminant((*_1));        // scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:12: 13:31
+          switchInt(move _3) -> [1_isize: bb1, otherwise: bb3]; // scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:12: 13:31
+      }
+  
+      bb1: {
+          _2 = discriminant((*(((*_1) as Some).0: &E))); // scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:12: 13:31
+          switchInt(move _2) -> [1_isize: bb2, otherwise: bb3]; // scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:12: 13:31
+      }
+  
+      bb2: {
+          _0 = const 1_u32;                // scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:38: 13:39
+          return;                          // scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:5: 13:52
+      }
+  
+      bb3: {
+          _0 = const 2_u32;                // scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:49: 13:50
+          return;                          // scope 0 at $DIR/early_otherwise_branch_soundness.rs:13:5: 13:52
+      }
+  }
+  

src/test/mir-opt/early_otherwise_branch_soundness.rs

@@ -0,0 +1,32 @@
+// compile-flags: -Z mir-opt-level=4 -Zunsound-mir-opts
+
+// Tests various cases that the `early_otherwise_branch` opt should *not* optimize
+
+// From #78496
+enum E<'a> {
+    Empty,
+    Some(&'a E<'a>),
+}
+
+// EMIT_MIR early_otherwise_branch_soundness.no_downcast.EarlyOtherwiseBranch.diff
+fn no_downcast(e: &E) -> u32 {
+    if let E::Some(E::Some(_)) = e { 1 } else { 2 }
+}
+
+// SAFETY: if `a` is `Some`, `b` must point to a valid, initialized value
+// EMIT_MIR early_otherwise_branch_soundness.no_deref_ptr.EarlyOtherwiseBranch.diff
+unsafe fn no_deref_ptr(a: Option<i32>, b: *const Option<i32>) -> i32 {
+    match a {
+        // `*b` being correct depends on `a == Some(_)`
+        Some(_) => match *b {
+            Some(v) => v,
+            _ => 0,
+        },
+        _ => 0,
+    }
+}
+
+fn main() {
+    no_downcast(&E::Empty);
+    unsafe { no_deref_ptr(None, std::ptr::null()) };
+}