Store a full Ty with each Value.

Author: cjgillot

compiler/rustc_mir_transform/src/gvn.rs

@@ -56,7 +56,7 @@ pub unsafe fn undef_union_as_integer() -> u32 {
 pub unsafe fn unreachable_direct() -> ! {
     // CHECK-LABEL: fn unreachable_direct(
     // CHECK: = const ();
-    // CHECK: = const () as Never (Transmute);
+    // CHECK: = const ZeroSized: Never;
     let x: Never = unsafe { transmute(()) };
     match x {}
 }

tests/mir-opt/const_prop/transmute.rs

@@ -15,7 +15,7 @@
 -         _2 = ();
 -         _1 = move _2 as Never (Transmute);
 +         _2 = const ();
-+         _1 = const () as Never (Transmute);
++         _1 = const ZeroSized: Never;
           unreachable;
       }
   }

tests/mir-opt/const_prop/transmute.unreachable_direct.GVN.32bit.diff

@@ -15,7 +15,7 @@
 -         _2 = ();
 -         _1 = move _2 as Never (Transmute);
 +         _2 = const ();
-+         _1 = const () as Never (Transmute);
++         _1 = const ZeroSized: Never;
           unreachable;
       }
   }

tests/mir-opt/const_prop/transmute.unreachable_direct.GVN.64bit.diff

@@ -18,7 +18,8 @@
 
       bb0: {
           _4 = copy _1 as *const T (PtrToPtr);
-          _5 = PtrMetadata(copy _4);
+-         _5 = PtrMetadata(copy _4);
++         _5 = const ();
           _6 = copy _1 as *const (&A, [T]) (PtrToPtr);
 -         _7 = PtrMetadata(copy _6);
 +         _7 = PtrMetadata(copy _1);

tests/mir-opt/gvn.generic_cast_metadata.GVN.panic-abort.diff

@@ -18,7 +18,8 @@
 
       bb0: {
           _4 = copy _1 as *const T (PtrToPtr);
-          _5 = PtrMetadata(copy _4);
+-         _5 = PtrMetadata(copy _4);
++         _5 = const ();
           _6 = copy _1 as *const (&A, [T]) (PtrToPtr);
 -         _7 = PtrMetadata(copy _6);
 +         _7 = PtrMetadata(copy _1);

tests/mir-opt/gvn.generic_cast_metadata.GVN.panic-unwind.diff

@@ -869,7 +869,7 @@ fn generic_cast_metadata<T, A: ?Sized, B: ?Sized>(ps: *const [T], pa: *const A,
 
             // Metadata usize -> (), do not optimize.
             // CHECK: [[T:_.+]] = copy _1 as
-            // CHECK-NEXT: PtrMetadata(copy [[T]])
+            // CHECK-NEXT: const ();
             let t1 = CastPtrToPtr::<_, *const T>(ps);
             let m1 = PtrMetadata(t1);