- // MIR for `main` before GVN
+ // MIR for `main` after GVN
  
  fn main() -> () {
      let mut _0: ();
      let _1: i32;
      let mut _2: i32;
      let mut _3: std::boxed::Box<i32>;
      let mut _4: usize;
      let mut _5: usize;
      let mut _6: *mut u8;
      let mut _7: std::boxed::Box<i32>;
      let mut _8: *const i32;
      let mut _9: *const i32;
      scope 1 {
          debug x => _1;
      }
  
      bb0: {
          StorageLive(_1);
-         StorageLive(_2);
+         nop;
          StorageLive(_3);
-         _4 = SizeOf(i32);
-         _5 = AlignOf(i32);
-         _6 = alloc::alloc::exchange_malloc(move _4, move _5) -> [return: bb1, unwind continue];
+         _4 = const 4_usize;
+         _5 = const 4_usize;
+         _6 = alloc::alloc::exchange_malloc(const 4_usize, const 4_usize) -> [return: bb1, unwind continue];
      }
  
      bb1: {
          StorageLive(_7);
          _7 = ShallowInitBox(move _6, i32);
          _8 = copy (((_7.0: std::ptr::Unique<i32>).0: std::ptr::NonNull<i32>).0: *const i32);
          (*_8) = const 42_i32;
          _3 = move _7;
          StorageDead(_7);
          _9 = copy (((_3.0: std::ptr::Unique<i32>).0: std::ptr::NonNull<i32>).0: *const i32);
          _2 = copy (*_9);
-         _1 = Add(move _2, const 0_i32);
-         StorageDead(_2);
+         _1 = copy _2;
+         nop;
          drop(_3) -> [return: bb2, unwind: bb3];
      }
  
      bb2: {
          StorageDead(_3);
          _0 = const ();
          StorageDead(_1);
          return;
      }
  
      bb3 (cleanup): {
          resume;
      }
  }