Add FileCheck for unit testing

[jackkoenig]

Draft to see if the process works end-to-end

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• Internal or build-related (includes code refactoring/cleanup)

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[seldridge]

This looks amazing. The tests can really be bulletproof now.

Two thoughts:

1. Is there any way to avoid needing to package FileCheck ourselves?
2. This follows a pattern of FileCheck usage where the checks are all after the code. I tend to use this frequently. However, I will sometimes also write in-line tests. Is there a way that we could support this as well, e.g., something like:

val fileCheck = new FileCheck()

class Foo extends RawModule {
  fileCheck("CHECK-LABEL: module Foo")
  val a = IO(Input(Bool()))
  fileCheck("CHECK-NEXT: input a: UInt<1>")
}

fileCheck.check(ChiselStage.emitCHIRRTL(new Foo))

This can be handled in a follow-on.

[seldridge]

This is sooooooooo much better. 💯

[mwachs5]

can we add something to the readme before this is merged with the link to primer/docs for those not familiar with file check syntax?

[jackkoenig]

@mwachs5 I added instructions on how to install and a very brief description of FileCheck and where to look for more information. How much of a tutorial do you think we need to include?

[sequencer]

Just wonder if possible to share the cases among firrtl, verilog.

[seldridge]

Just wonder if possible to share the cases among firrtl, verilog.

FileCheck has support for checking multiple prefixes which is commonly used to share across separate invocations of some test run. This may work for sharing between firrtl and verilog, but is unlikely.

[seldridge]

For this and the other method, just a t: => String is probably more useful as I can see wanting to use this to check SystemVerilog emission. It isn't too onerous to have a user do fileCheck(ChiselStage.emitCHIRRTL(new Foo)).

[jackkoenig]

Capturing stdout and stderr is kind of annoying though, maybe I'll provide a 3rd method that just takes a String, and have the other 2 call it?

[seldridge]

That works!