I still have _T signals, can this be fixed?

First check - is the compiler plugin properly enabled? Scalac plugins are enabled via the scalac option -Xplugin:<path/to/jar>. You can check which compiler plugins are enabled by running show Compile / scalacOptions in the sbt prompt.

If the plugin is enabled, these signals could be intermediate values which are consumed by either assertions or when predicates. In these cases, the compiler plugin often can’t find a good prefix for the generated intermediate signals. We recommend you manually insert calls to prefix to fix these cases. We did this to Rocket Chip and saw huge benefits!

I still see _GEN signals, can this be fixed?

_GEN signals are usually generated from the FIRRTL compiler, rather than the Chisel library. We are working on renaming these signals with more context-dependent names, but it is a work in progress. Thanks for caring!

My module names are super unstable - I change one thing and Queue_1 becomes Queue_42. Help!

This is the infamous Queue instability problem. In general, these cases are best solved at the source - the module itself! If you overwrite desiredName to include parameter information (see the explanation for more info), then this can avoid this problem permanantly. We’ve done this with some Chisel utilities with great results!

I want to add some hardware or assertions, but each time I do all the signal names get bumped!

This is the classic “ECO” problem, and we provide descriptions in explanation. In short, we recommend wrapping all additional logic in a prefix scope, which enables a unique namespace. This should prevent name collisions, which are what triggers all those annoying signal name bumps!

I want to force a signal (or instance) name to something, how do I do that?

Use the .suggestName method, which is on all classes which subtype ‘Data’.

All this prefixing is annoying, how do I fix it?

You can use the noPrefix { ... } to strip the prefix from all signals generated in that scope.

class ExampleNoPrefix extends MultiIOModule {
  val in = IO(Input(UInt(2.W)))
  val out = IO(Output(UInt()))

  val add = noPrefix { in + in + in }

  out := add
}

println(ChiselStage.emitVerilog(new ExampleNoPrefix))
// [info] [0.144] Elaborating design...
// [info] [0.255] Done elaborating.
// module ExampleNoPrefix(
//   input        clock,
//   input        reset,
//   input  [1:0] in,
//   output [1:0] out
// );
//   wire [1:0] _T_1 = in + in; // @[naming.md 30:27]
//   assign out = _T_1 + in; // @[naming.md 30:32]
// endmodule
//