The onnx-mlir compiler supports loading configuration from a JSON file, allowing you to specify compile options and operation-specific settings in a single, reusable configuration file.

Features

• Compile Options: Specify command-line options as an array in the config file. These are prepended to the options provided on the command line. Thus, the options to onnx-mlir are options_from_confifg_file + options_from_command_line, meaning that the options provided on the commmand line may override the options in the config file.
• Default Config: Automatically loads omconfig.json from the same directory as the input model if present.
• Custom Config: Use --config-file to specify a custom configuration file.

JSON Scheme Description

Example:

{
  "compile_options": ["-O3", "-march=z16"]
}

Top-Level Keys

Key	Type	Description
compile_options	array of string (optional)	A list of compiler command-line options that are prepended to the existing command-line arguments.

Example:

"compile_options": ["-O3", "-march=z16", "--parallel"]

Supported Options:

• Optimization levels: -O0, -O1, -O2, -O3
• Target architecture: -march=<arch>, -mcpu=<cpu>, -mtriple=<triple>
• Accelerator: -maccel=NNPA
• Parallelization: --parallel
• And all other onnx-mlir command-line options

Usage

Using Default Config File

Create omconfig.json in the same directory as your input model:

cat > omconfig.json << 'EOF'
{
  "compile_options": ["-O3", "-march=z16"]
}
EOF

# Config is automatically loaded
onnx-mlir model.onnx

Using Custom Config File

onnx-mlir --config-file=my-config.json model.onnx

Config File Overrides CLI Options

Config file options take precedence over command-line settings:

# Config file has -O3 but CLI overrrides to -02
onnx-mlir -O2 --config-file=config.json model.onnx
# Result: Uses -O2 from CLI

Migration from Command Line

If you have a complex command line:

onnx-mlir -O3 -march=z16 --parallel -j 8 model.onnx

Convert it to a config file:

{
  "compile_options": ["-O3", "-march=z16", "--parallel", "-j 8"]
}

Then use:

onnx-mlir --config-file=config.json model.onnx

Troubleshooting

Config File Not Found

If the config file doesn't exist, onnx-mlir continues without error (unless you explicitly specify --config-file).

Parse Errors

If the JSON is malformed, you'll see an error message:

Warning: Failed to parse config file: config.json

Invalid Options

If the config contains invalid compiler options, you'll see the standard option parsing error.

Debugging

To see which options were loaded from the config, use -v:

onnx-mlir --config-file=config.json model.onnx -v
# Output contains the following information:
# Config file: config.json
# Onnx-mlir command: ./Debug/bin/onnx-mlir -O2 -march=z16 --config-file=config.json model.onnx -v

Related Documentation

• Compiler Options