Add asm label support to THIR

compiler/rustc_middle/src/thir.rs

@@ -565,6 +565,9 @@ pub enum InlineAsmOperand<'tcx> {
     SymStatic {
         def_id: DefId,
     },
+    Label {
+        block: BlockId,
+    },
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, HashStable)]

compiler/rustc_middle/src/thir/visit.rs

@@ -162,6 +162,7 @@ pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
                     | Const { value: _, span: _ }
                     | SymFn { value: _, span: _ }
                     | SymStatic { def_id: _ } => {}
+                    Label { block } => visitor.visit_block(&visitor.thir()[*block]),
                 }
             }
         }