sass-diff

# SASS Diffs Use this when asked to check for SASS changes between commits, branches or a local changeset. ## Goal Detect relevant changes in generated CUDA machine code (i.e. SASS) while filtering noise from addresses, symbols, metadata, etc. Any non-trivial change must be detected. ## Inputs to establish * Compilation target under test * The CUDA SM architectures to compile for. Try to detect this from the code and offer the user a list of suggestions. The user must confirm or provide this list. * Baseline source (e.g. the previous commit/branch or the current commit without the changes in the working copy). * Comparison source (e.g. the current commit/branch or the current commit with the changes in the working copy). * Whether a SASS (default) or PTX diff is requested. ## Disassembly listing generation * Compile both, the baseline and comparison source, with the same compiler flags and options. When not specified otherwise, lookup the options from `compile_commands.json` or the current build system (i.e. CMake files). Make sure the CUDA SM architectures (`CMAKE_CUDA_ARCHITECTURES`) are set to the user-provided or approved list. * Dump the disassembly from the binaries produced in the previous set using `cuobjdump -sass` or `cuobjdump -ptx`. ## Comparison rules (what matters) Ignore as trivial: * Register renaming with identical instruction sequence and operands. * Pure label renumbering or reordering of identical basic blocks. * Formatting-only differences or reordered symbol tables. * Changes to symbol names (global function names) ## Reporting * If any non-trivial change was detected, report the top 5 regions where a non-trivial change was detected, including the name of the kernel they appeared in. * Provide a short summary of the diff type, including opcode changes, memory access size/cache policy changes, control-flow changes, register-count changes, spills/local memory, shared memory, and occupancy-relevant resource deltas. * Explicitly state if only noise was detected. * If you are not sure if the differences are impactful, show it and ask the user for guidance. * Keep the disassembly dumps available and tell the user where they can find them.