Added another small test to gvn storage

Author: ohadravid

tests/mir-opt/gvn_storage_issue_141649.f_dead.GVN.diff

@@ -0,0 +1,22 @@
+- // MIR for `f_dead` before GVN
++ // MIR for `f_dead` after GVN
+  
+  fn f_dead(_1: u32) -> () {
+      let mut _0: ();
+      let mut _2: S;
+      let mut _3: S;
+  
+      bb0: {
+-         StorageLive(_2);
++         nop;
+          _2 = S(copy _1, const 2_u32);
+-         StorageDead(_2);
++         nop;
+          StorageLive(_3);
+-         _3 = S(copy _1, const 2_u32);
++         _3 = copy _2;
+          StorageDead(_3);
+          return;
+      }
+  }
+  

tests/mir-opt/gvn_storage_issue_141649.rs

@@ -2,6 +2,7 @@
 //@ test-mir-pass: GVN
 // EMIT_MIR gvn_storage_issue_141649.f.GVN.diff
 // EMIT_MIR gvn_storage_issue_141649.f_borrowed.GVN.diff
+// EMIT_MIR gvn_storage_issue_141649.f_dead.GVN.diff
 
 #![feature(custom_mir, core_intrinsics)]
 
@@ -57,3 +58,26 @@ pub fn f_borrowed(_1: u32) {
         }
     }
 }
+
+#[custom_mir(dialect = "runtime")]
+pub fn f_dead(_1: u32) {
+    // CHECK-LABEL: fn f_dead(
+    mir! {
+        let _2: S;
+        let _3: S;
+        {
+            // CHECK-NOT: StorageLive(_2);
+            // CHECK: StorageLive(_3);
+            // CHECK: _3 = copy _2;
+            // CHECK: StorageDead(_3);
+            // CHECK-NOT: StorageDead(_2);
+            StorageLive(_2);
+            _2 = S(_1, 2);
+            StorageDead(_2);
+            StorageLive(_3);
+            _3 = S(_1, 2);
+            StorageDead(_3);
+            Return()
+        }
+    }
+}