Maintain variable names post-compilation

[ghost]

I would really appreciate a feature to maintain variable naming post-compilation to VHDL or Verilog like MyHDL. As of now the code that clash outputs is very difficult to read or reason about its connection to the initial Haskell.

[christiaanb]

I'm currently working on fixing blockRam inference for Xilinx Vivado. Afterwards, I'll take a look at this.

[christiaanb]

I'm making progress on this. Some notes:

• Given the following Haskell written by the user:

  f (x,y) = ...

  I get the following code from the GHC Haskell compiler:

  f ds = case ds of (x,y) -> ...

  which I translate to a component f with a single input port called ds, and not, as one might expect, a component f with two inputs ports x and y. The problem is, is that I cannot distinguish between f ds = case ds of (x,y) -> ... written by the user, or f ds = case ds of (x,y) -> ... generated by the GHC Haskell compiler. I don't plan to add any heuristics as to what might be generated or not, so I will always create the single input-port version of the component f.

• GHC generates a lot of so-called worker/wrapper function pairs, where you have the user-written function f, which becomes the wrapper, and the compiler optimized function f', the worker. Now, most of the "optimized" functions are actually only running faster when they would be executed on a normal CPU, when translating them to circuits, it makes absolutely no difference. Also, the worker/wrapper transformation does some name-mangling on the argument names, meaning that it is currently sometimes hard to preserve names in the HDL output. However, once GHC8 is released, and I can base CLaSH on top of GHC8, I can finally disable the worker/wrapper transformation, and hence no longer have the annoying name-mangling.

[christiaanb]

Some of the name-preservation improvements are part of the 0.6.11 release of CLaSH. I'll keep this issue open, as I'm sure we can do better than what's currently implemented.

[christiaanb]

Clash preserves most names these days; and when it doesn't you simply add a {-# NOINLINE xyz #-} pragma