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diff --git a/doc/NOTES.md b/doc/NOTES.md deleted file mode 100644 index 5e08b7e..0000000 --- a/doc/NOTES.md +++ /dev/null @@ -1,83 +0,0 @@ -Parser generators in Rust: --------------------------- -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 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 - -Implicit conversions --------------------- -* PTX support for implicit conversions is completely degenerate, docs say: -_For convenience, ld, st, and cvt instructions permit source and destination data operands to be wider than the instruction-type size, so that narrow values may be loaded, stored, and converted using regular-width registers. For example, 8-bit or 16-bit values may be held directly in 32-bit or 64-bit registers when being loaded, stored, or converted to other types and sizes_ -Which is sensible, but completely untrue. In reality ptxas compiles silly code like this: - ``` - param.f32 param_1 - ... - .reg.s32 %r1 - ld.param.b16 %r1, [param_1]; - ``` -* Surprise, surprise, there's two kind of implicit conversions at play in the example above: - * "Relaxed type-checking rules": this is the conversion of b16 operation type to s32 dst register - * Undocumented type coercion when dereferencing param_1. The PTX behaviour is to coerce **every** type. It's something to the effect of `[param_1] = *(b16*)param_1` - -PTX grammar ------------ -* PTX grammar rules are atrocious, keywords can be freely reused as ids without escaping -* Modifiers can be applied to instructions in any arbitrary order. We don't support it and hope we will never have to - - -Rust debugging --------------- -* Nothing works 100% well on vscode/Windows: - * MSVC/lldb - always garbage (simple enums are fubar) - * MSVC/cppvsdbg - sometimes garbage (nested enums are fubar) - * GNU/lldb - mostly fine, but can't follow child processes - * GNU/gdb - always garbage (I don't have the patience to manually QA rust-gdb on Windows) and doesn't quite understand file paths for break points -* Neither on vscode/Linux: - * lldb - mostly fine, but can't follow child processes - * gdb - visualizes variables somewhat awkardly (shows all possible variants of an enum) -* CLion could be the solution, but intellij-rust can't load this project - -CUDA <-> L0 ------------ -* device ~= device -* stream ~= command queue -* context ~= context (1.0+) -* graph ~= command list -* module ~= module - -IGC ---- -* IGC is extremely brittle and segfaults on fairly innocent code: - * OpBitcast of pointer to uint - * OpCopyMemory of alloca'd variable |