Do not emit alloca for ZST local even if it is uninitialized

src/test/codegen/naked-functions.rs

@@ -9,7 +9,6 @@
 #[naked]
 pub fn naked_empty() {
     // CHECK-NEXT: {{.+}}:
-    // CHECK-NEXT: %0 = alloca {}, align 1
     // CHECK-NEXT: ret void
 }
 
@@ -19,7 +18,6 @@ pub fn naked_empty() {
 // CHECK-NEXT: define void @naked_with_args(i{{[0-9]+( %a)?}})
 pub fn naked_with_args(a: isize) {
     // CHECK-NEXT: {{.+}}:
-    // CHECK-NEXT: %0 = alloca {}, align 1
     // CHECK: ret void
 }
 

src/test/run-make/const_fn_mir/dump.mir

@@ -12,7 +12,6 @@ fn main() -> () {
     }
 
     bb1: {
-        _0 = const ();                   // scope 0 at main.rs:8:11: 10:2
         return;                          // scope 0 at main.rs:10:2: 10:2
     }
 }