Function visit_block_succs

cranelift/codegen/src/inst_predicates.rs:169–224

Visit all successors of a block with a given visitor closure. The closure arguments are the branch instruction that is used to reach the successor, the successor block itself, and a flag indicating whether the block is branched to via a table entry.

(
    f: &Function,
    block: Block,
    mut visit: F,
)

/// the successor block itself, and a flag indicating whether the block is
/// branched to via a table entry.
pub(crate) fn visit_block_succs<F: FnMut(Inst, Block, bool)>(
    f: &Function,
    block: Block,
    mut visit: F,
) {
    if let Some(inst) = f.layout.last_inst(block) {
        match &f.dfg.insts[inst] {
            ir::InstructionData::Jump {
                destination: dest, ..
            } => {
                visit(inst, dest.block(&f.dfg.value_lists), false);
            }

            ir::InstructionData::Brif {
                blocks: [block_then, block_else],
                ..
            } => {
                visit(inst, block_then.block(&f.dfg.value_lists), false);
                visit(inst, block_else.block(&f.dfg.value_lists), false);
            }

            ir::InstructionData::BranchTable { table, .. } => {
                let pool = &f.dfg.value_lists;
                let table = &f.stencil.dfg.jump_tables[*table];

                // The default block is reached via a direct conditional branch,
                // so it is not part of the table. We visit the default block
                // first explicitly, to mirror the traversal order of
                // `JumpTableData::all_branches`, and transitively the order of
                // `InstructionData::branch_destination`.
                //
                // Additionally, this case is why we are unable to replace this
                // whole function with a loop over `branch_destination`: we need
                // to report which branch targets come from the table vs the
                // default.
                visit(inst, table.default_block().block(pool), false);

                for dest in table.as_slice() {
                    visit(inst, dest.block(pool), true);
                }
            }

            ir::InstructionData::TryCall { exception, .. }
            | ir::InstructionData::TryCallIndirect { exception, .. } => {
                let pool = &f.dfg.value_lists;
                let exdata = &f.stencil.dfg.exception_tables[*exception];

                for dest in exdata.all_branches() {
                    visit(inst, dest.block(pool), false);
                }
            }

            inst => debug_assert!(!inst.opcode().is_branch()),
        }
    }
}