Move default blocks into jump tables (#5756)

Move the default block off of the br_table instrution, and into the JumpTable that it references.

cranelift/frontend/src/frontend.rs

@@ -129,9 +129,7 @@ impl<'short, 'long> InstBuilderBase<'short> for FuncInstBuilder<'short, 'long> {
                 }
             }
 
-            ir::InstructionData::BranchTable {
-                table, destination, ..
-            } => {
+            ir::InstructionData::BranchTable { table, .. } => {
                 // Unlike all other jumps/branches, jump tables are
                 // capable of having the same successor appear
                 // multiple times, so we must deduplicate.
@@ -144,9 +142,12 @@ impl<'short, 'long> InstBuilderBase<'short> for FuncInstBuilder<'short, 'long> {
                     .jump_tables
                     .get(*table)
                     .expect("you are referencing an undeclared jump table")
-                    .iter()
-                    .filter(|&dest_block| unique.insert(*dest_block))
+                    .all_branches()
                 {
+                    if !unique.insert(*dest_block) {
+                        continue;
+                    }
+
                     // Call `declare_block_predecessor` instead of `declare_successor` for
                     // avoiding the borrow checker.
                     self.builder
@@ -154,7 +155,6 @@ impl<'short, 'long> InstBuilderBase<'short> for FuncInstBuilder<'short, 'long> {
                         .ssa
                         .declare_block_predecessor(*dest_block, inst);
                 }
-                self.builder.declare_successor(*destination, inst);
             }
 
             inst => debug_assert!(!inst.opcode().is_branch()),