Add Python config API for NPU backend settings

[erwei-xilinx]

Summary

• Adds amd_triton_npu/backend/config.py with a singleton npu_config object that provides programmatic control over 5 settings previously only available via environment variables
• Replaces all ad-hoc os.getenv calls in driver.py and compiler.py with reads from the config singleton
• Eliminates the duplicated _get_air_project_path() function that existed in both files

API

from triton.backends.amd_triton_npu.config import npu_config, set_config, config_context

# Direct attribute assignment
npu_config.bf16_emulation = True
npu_config.compile_only = True
npu_config.air_project_path = "/tmp/my_project"
npu_config.transform_tiling_script = "/path/to/tiling.mlir"
npu_config.output_format = "elf"  # or "xclbin" or None for auto-detect

# Dict-style
set_config(bf16_emulation=True, compile_only=False)

# Context manager for temporary overrides
with config_context(compile_only=True):
    kernel[grid](a, b, c)

All existing environment variables continue to work as fallback defaults — fully backward compatible.

Config property	Env var fallback	Default
compile_only	AMD_TRITON_NPU_COMPILE_ONLY	False
transform_tiling_script	AIR_TRANSFORM_TILING_SCRIPT	None
bf16_emulation	AMD_TRITON_NPU_BF16_EMULATION	False
output_format	AMD_TRITON_NPU_OUTPUT_FORMAT	None (auto-detect)
air_project_path	AMD_TRITON_NPU_AIR_PROJECT_PATH	./air_project

Closes #43

Test plan

• Verify import works: python -c "from triton.backends.amd_triton_npu.config import npu_config, set_config, config_context"
• Verify env var fallback: AMD_TRITON_NPU_COMPILE_ONLY=1 python -c "from triton.backends.amd_triton_npu.config import npu_config; assert npu_config.compile_only"
• Verify programmatic override wins over env var: AMD_TRITON_NPU_BF16_EMULATION=1 python -c "from triton.backends.amd_triton_npu.config import npu_config; npu_config.bf16_emulation = False; assert not npu_config.bf16_emulation"
• Run existing examples with env vars to verify no regressions

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds a process-global Python configuration API for the AMD Triton NPU backend, enabling programmatic control of backend settings that were previously only configurable via environment variables, while keeping env vars as backward-compatible fallbacks.

Changes:

• Introduces amd_triton_npu/backend/config.py exposing a singleton npu_config, plus set_config() and config_context() for overrides.
• Replaces direct os.getenv(...) reads in the driver/compiler with npu_config properties and removes duplicated air project path helper logic.
• Adds amd_triton_npu/backend/__init__.py to support package/module structure.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
amd_triton_npu/backend/config.py	New config singleton + helpers with env-var fallbacks
amd_triton_npu/backend/driver.py	Swaps env var reads for config access; removes duplicated path helper
amd_triton_npu/backend/compiler.py	Uses config for air project path dumping; removes duplicated helper
amd_triton_npu/backend/__init__.py	Adds package marker for backend module

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[ypapadop-amd]

I think we should also add #44