Today we're releasing Spade 0.13, one of the biggest Spade releases yet! It includes gen if for compile time conditionals and recursion, lots of namespacing fixes, improvements to handling external Verilog, and lots more.

gen if🔗

gen if allows you to conditionally branch based on type parameters. The primary use case for this is recursively iterating over arrays. For example, you can now write a function that adds one to every element in an array like this

fn add_one<#W, #N>(x: [int<W>; N]) -> [int<{W+1}>; N] {
  gen if N == 0 {
    []
  } else {
    [x[0] + 1] `concat_arrays` add_one(x[1:N])
  }
}

While this is useful for some things in isolation, it is going to lay the groundwork for more complex generic constructs in later releases, especially once lambdas are implemented.

Interacting with external Verilog🔗

This release changes the syntax of the old __builtin__ marker to extern to make it less hacky and more clear what it does. The #[no_mangle] attribute has also been given a all parameter which blanket applies #[no_mangle] to all parameters.

What used to look like this:

entity external_verilog(
  #[no_mangle] clk: clock,
  #[no_mangle] a: uint<8>,
  #[no_mangle] b: uint<8>,
  #[no_mangle] out: inv &uint<8>
) __builtin__

now looks like this

#[no_mangle(all)]
extern entity external_verilog(clk: clock, a: uint<8>, b: uint<8>, out: inv &uint<8>);

Including external Verilog in Swim has also been improved, there is now a [verilog] and [synthesis.verilog] section in swim.toml which allows you to both include specific Verilog files, and specify include directories.

You can now also use where clauses on extern units.

Thanks to Ethan for all these changes!

Namespacing changes🔗

The namespacing system has seen several improvements in this release. The most user facing change is that all modules now need a main.spade at the root of the module, and for other files to be included in the project, you need to add mod filename; to the corresponding main.spade. For rust users, this will feel very familiar, what rust calls main.rs, lib.rs and mod.rs are all called main.spade.

The namespace of the main.spade file has also changed, a main.spade with

fn a() {}

in a project called project would previously result in project::main::a, now it results in project::a;

There have also been several bug fixes and improvements in the name resolution system including

• use statements of undefined names now error on the use instead of when using the used name.
• use between namespaces now works as expected
• No more stack overflows or infinite recursion if use-ing a single identifier

Thanks to DasLixou for most of these fixes!

Expressions are now statements🔗

If you wanted to call a unit with "side effects" previously, you would have had to write

let _ = inst unit(some_port);

now you can just write

inst unit(some_port);

Improved const generics🔗

You can use const generics in unit parameter and output types, which means you no longer have to add "internal" type parameters and where clauses. For example, you can now write

fn weird_operation<#uint N>(a: uint<N>, b: uint<{N+5}>) -> uint<{N/2}> {}

Synchronous Resets🔗

Spade now uses synchronous resets for all registers instead of asynchronous.

Other fixes🔗

There have also been numerous small fixes and improvements that don't fit in this blog post, you can read them all in the Changelog

SPADETID!🔗

Frans has started regularly streaming Spade development on https://www.twitch.tv/thezoq2/. If you want to be notified when this happens, you can join the discord and give yourself the SPADETID role.