ZLUDA/doc/NOTES.md

I'm convinced nobody actually uses parser generators in Rust:

• pomelo can't generate lexer (understandable, as it is a port of lemon and lemon can't do this either)
• pest can't do parse actions, you have to convert your parse tree to ast manually
• lalrpop can't do comments
  • and the day I wrote the line above it can
  • reports parsing errors as byte offsets
  • if you want to skip parsing one of the alternatives, functional design gets quite awkward
• antlr4rust is untried and requires java to build
• no library supports island grammars

What to emit?

• SPIR-V
  • Better library support, easier to emit
  • Can by optimized by IGC
  • Can't do some things (not sure what exactly yet)
  • But we can work around things with inline VISA
• VISA
  • Quicker compilation

A64 vs BTS

• How to force A64: -cl-intel-greater-than-4GB-buffer-required
• PTX made a baffling desing choice: global pointers are represented as untyped 64bit integers
• Consequently, there's no 100% certain way to know which argument is a surface and which is a scalar
  • It seems that NVidia guys realized what a horrible idea that was and emit cvta.to.global as a marker for global pointers?
    • But it's only emitted in a recent release build, can't rely on it
    • Maybe debug builds emit debug metadata to detect surfaces?
    • Might add this as an optimization later
  • cuLaunchKernel docs say this: "The number of kernel parameters and their offsets and sizes do not need to be specified as that information is retrieved directly from the kernel's image", note the wording: offsets and sizes and not types
  • Wait, you can mark an argument as a pointer with .ptr: https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#kernel-parameter-attribute-ptr, but it's useless with NV compiler not emitting it
• Potential solution: compile only during the dispatch, when type of arguments is known?
  • Can't do, the set of arguments passed to cuLaunchKernel is untyped
• Solution: treat all arguments as untyped integers and say goodbye to BTS access