OK so I'm not really rewriting everything... just... a lot of it.

The current runtime infrastructure for Epoch is precarious at best, and desperately needs some improvements. There are a number of things I want to do that all happen to coincide nicely with a desire to rewrite the runtime system:

• Destroy the EpochLibrary DLL forever. This is an ancient crufty artifact that deserves death, and getting rid of it should simplify the entire build pipeline noticeably.
  
• Improve program start times. I've posted about this before; basically the Epoch runtime JIT compiles your program every time it starts up, which in the case of the compiler leads to about a 6 second stall. Gross.
  
• Emit true native binaries - tied in with the above point, I'd like to emit genuine native .EXE and .DLL files instead of mutant VM hybrid files. This will enable the use of things like dynamic linking which will be a huge win.
  
• Separate the compilation pipeline into modular pieces. Right now the parser is "reused" by brute-force including the code in both Era and the compiler itself; instead, I'd like to make the parser and AST stuff into DLLs that feed data around to each other.
  

I have a loose mental strategy for doing all this, which looks vaguely like the following:

• Build a new DLL (tentatively EpochLLVM) which wraps LLVM and allows the compiler to make simple C-API calls to set up LLVM IR and generate executable machine code from it.
  
• Retrofit the existing Epoch compiler to use this new DLL when generating binaries.
  
• Rebuild garbage collection and other runtime infrastructure in a separate DLL (tenatively EpochRuntime) or maybe a few DLLs.
  
• Self-host the compiler through this new chain.
  
• Convert Era to use the new chain.
  
• Build support for emitting Epoch DLLs.
  
• Proof-of-concept the DLL system by replacing the C++ lexer used for Scintilla syntax highlighting with the actual lexer.
  
• Split the remaining parser, AST, and codegen logic into separate DLLs.
  
• Self-host again using this new infrastructure.
  
• Ship Release 16.
  

This ought to keep me busy well through the end of the year...

The benefits will be huge though. In addition to being able to write Epoch DLLs, getting faster start times, and cleaning up the modularity of the code a lot, this will pave the way towards integrating higher-level source processing tools with Era, as well as giving me an opportunity to revisit some historical but gross decisions, like the use of UTF-16. Last but not least, it gets even more of the implementation of the language and tools moved into Epoch instead of C++.

Overall it's a daunting amount of work, but I think it can be managed. The real trick will be staying interested in the process during the long dark period where nothing quite works. I hope my skeletal plan will give me plenty of moments to sit back and enjoy visible progress, but we shall see.


So, here goes nothing!