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/codegen/meta/src/shared/entities.rs

@@ -15,10 +15,6 @@ pub(crate) struct EntityRefs {
     /// This is primarily used in control flow instructions.
     pub(crate) block_call: OperandKind,
 
-    /// A reference to a basic block in the same function.
-    /// This is primarily used in control flow instructions.
-    pub(crate) label: OperandKind,
-
     /// A reference to a basic block in the same function, with its arguments provided.
     /// This is primarily used in control flow instructions.
     pub(crate) block_then: OperandKind,
@@ -63,12 +59,6 @@ impl EntityRefs {
                 "a basic block in the same function, with its arguments provided.",
             ),
 
-            label: new(
-                "destination",
-                "ir::Block",
-                "a basic block in the same function.",
-            ),
-
             block_then: new(
                 "block_then",
                 "ir::BlockCall",

cranelift/codegen/meta/src/shared/formats.rs

@@ -117,7 +117,6 @@ impl Formats {
 
             branch_table: Builder::new("BranchTable")
                 .value()
-                .imm(&entities.label)
                 .imm(&entities.jump_table)
                 .build(),
 

cranelift/codegen/meta/src/shared/instructions.rs

@@ -19,7 +19,6 @@ fn define_control_flow(
 ) {
     let block_call = &Operand::new("block_call", &entities.block_call)
         .with_doc("Destination basic block, with its arguments provided");
-    let label = &Operand::new("label", &entities.label).with_doc("Destination basic block");
 
     ig.push(
         Inst::new(
@@ -93,7 +92,7 @@ fn define_control_flow(
         "#,
                 &formats.branch_table,
             )
-            .operands_in(vec![x, label, JT])
+            .operands_in(vec![x, JT])
             .branches(),
         );
     }