indirectbr

    pub fn indirectbr(
        self: *WipFunction,
        addr: Value,
        targets: []const Block.Index,
    ) Allocator.Error!Instruction.Index {
        try self.ensureUnusedExtraCapacity(1, Instruction.IndirectBr, targets.len);
        const instruction = try self.addInst(null, .{
            .tag = .indirectbr,
            .data = self.addExtraAssumeCapacity(Instruction.IndirectBr{
                .addr = addr,
                .targets_len = @intCast(targets.len),
            }),
        });
        _ = self.extra.appendSliceAssumeCapacity(@ptrCast(targets));
        for (targets) |target| target.ptr(self).branches += 1;
        return instruction;
    }