Rework br_table to use BlockCall (#5731)

Rework br_table to use BlockCall, allowing us to avoid adding new nodes during ssa construction to hold block arguments. Additionally, many places where we previously matched on InstructionData to extract branch destinations can be replaced with a use of branch_destination or branch_destination_mut.

cranelift/frontend/src/frontend.rs

@@ -130,6 +130,8 @@ impl<'short, 'long> InstBuilderBase<'short> for FuncInstBuilder<'short, 'long> {
             }
 
             ir::InstructionData::BranchTable { table, .. } => {
+                let pool = &self.builder.func.dfg.value_lists;
+
                 // Unlike all other jumps/branches, jump tables are
                 // capable of having the same successor appear
                 // multiple times, so we must deduplicate.
@@ -144,7 +146,8 @@ impl<'short, 'long> InstBuilderBase<'short> for FuncInstBuilder<'short, 'long> {
                     .expect("you are referencing an undeclared jump table")
                     .all_branches()
                 {
-                    if !unique.insert(*dest_block) {
+                    let block = dest_block.block(pool);
+                    if !unique.insert(block) {
                         continue;
                     }
 
@@ -153,7 +156,7 @@ impl<'short, 'long> InstBuilderBase<'short> for FuncInstBuilder<'short, 'long> {
                     self.builder
                         .func_ctx
                         .ssa
-                        .declare_block_predecessor(*dest_block, inst);
+                        .declare_block_predecessor(block, inst);
                 }
             }
 
@@ -691,7 +694,7 @@ impl<'a> FunctionBuilder<'a> {
     /// other jump instructions.
     pub fn change_jump_destination(&mut self, inst: Inst, old_block: Block, new_block: Block) {
         let dfg = &mut self.func.dfg;
-        for block in dfg.insts[inst].branch_destination_mut() {
+        for block in dfg.insts[inst].branch_destination_mut(&mut dfg.jump_tables) {
             if block.block(&dfg.value_lists) == old_block {
                 self.func_ctx.ssa.remove_block_predecessor(old_block, inst);
                 block.set_block(new_block, &mut dfg.value_lists);