feat: flash attention support for hexagon-npu

[chraac]

Related to chraac/llama.cpp#45

[Copilot]

Pull Request Overview

Adds Flash Attention support for the Hexagon NPU backend by enhancing log parsing, test coverage, CLI scripts, and documentation.

• Extend log_parser and its tests to recognize FLASH_ATTN_EXT operations
• Introduce --flash-attn flags in device‐run and benchmark scripts (bash and PowerShell)
• Update build docs with Hexagon SDK requirements and add a Python test workflow

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
scripts/tests/test_log_parser.py	Expanded unit tests to cover FLASH_ATTN_EXT parsing
scripts/run_device_model.sh	Added -f/--flash-attn argument and forwarding in bash script
scripts/run_device_model.ps1	Added -f/--FlashAttention switch and arg assembly in PS script
scripts/log_parser.py	Implemented parsing and item subclassing for FLASH_ATTN_EXT
scripts/batch_run_benchmarks_and_save_log.sh	Added --flash-attn support for bash benchmark runner
scripts/batch_run_benchmarks_and_save_log.ps1	Added -f/--FlashAttention support for PowerShell benchmark
llama.cpp	Updated submodule commit reference
docs/how-to-build.md	Added instructions to install Hexagon SDK
.github/workflows/python_tests.yml	New workflow to run Python unit tests for log parser

Comments suppressed due to low confidence (3)

scripts/tests/test_log_parser.py:8

• [nitpick] The test name suggests checking a method called get_name, but it actually verifies dtype, shape, and permute behavior. Consider renaming to test_op_tensor_initialization_sets_dtype_shape_and_permute for clarity.

    def test_given_op_tensor_when_get_name_then_return_correct_name(self):

.github/workflows/python_tests.yml:41

• This step is labeled Test with pytest but invokes the unittest module incorrectly. Either switch to pytest invocation or use python -m unittest test_log_parser -v to run the tests as written.

        python3 -m test_log_parser -v

scripts/log_parser.py:131

• [nitpick] The return type hint dict[str:(...)] is invalid Python syntax. Consider using dict[str, Union[OpTensor.DataType, int, float, bool, list]] or the -> Dict[str, Any] pattern to satisfy type checkers.

    def __parse_prop(prop: str) -> dict[str:(OpTensor.DataType | int | float | bool | list)]:

[Copilot]

The variable $extraArgs is only set inside the if ($Verbose) block and may be undefined here. Initialize $extraArgs = "" before any conditionals to prevent null or concatenation errors.