data/markdown/OR_userguide/OR_rmp_README.md

Restructure

The restructure module in OpenROAD (rmp) is based on an interface to ABC for local resynthesis. The package allows logic restructuring that targets area or timing. It extracts a cloud of logic using the OpenSTA timing engine, and passes it to ABC through blif interface. Multiple recipes for area or timing are run to obtain multiple structures from ABC; the most desirable among these is used to improve the netlist. The ABC output is read back by a blif reader which is integrated to OpenDB. blif writer and reader also support constants from and to OpenDB. Reading back of constants requires insertion of tie cells which should be provided by the user as per the interface described below.

Commands

- Parameters in square brackets `[-param param]` are optional.
- Parameters without square brackets `-param2 param2` are required.

Restructuring can be done in two modes: area or delay.

Area Mode

restructure 
    -liberty_file liberty_file
    -target area
    -tielo_pin  tielo_pin_name
    -tiehi_pin  tiehi_pin_name
    -work_dir  workdir_name

Timing Mode

restructure 
    -liberty_file liberty_file
    -target timing
    -slack_threshold slack_val
    -depth_threshold depth_threshold
    -tielo_pin  tielo_pin_name
    -tiehi_pin  tiehi_pin_name
    -work_dir  workdir_name

Options

Switch Name	Description
-liberty_file	Liberty file with description of cells used in design. This is passed to ABC.
-target	Either area or delay. In area mode, the focus is area reduction, and timing may degrade. In delay mode, delay is likely reduced, but the area may increase. The default value is area.
-slack_threshold	Specifies a (setup) timing slack value below which timing paths need to be analyzed for restructuring. The default value is 0, and the allowed values are floats [0, MAX_FLOAT].
-depth_threshold	Specifies the path depth above which a timing path would be considered for restructuring. The default value is 16, and the allowed values are [0, MAX_INT].
-tielo_pin	Tie cell pin that can drive constant zero. The format is <cell>/<port>.
-tiehi_pin	Tie cell pin that can drive constant one. The format is <cell>/<port>.
-work_dir	Name of the working directory for temporary files. If not provided, run directory would be used.

Example scripts

Example scripts on running rmp for a sample design of gcd as follows:

./test/gcd_restructure.tcl

Regression tests

There are a set of regression tests in ./test. For more information, refer to this section.

Simply run the following script:

./test/regression

Limitations

FAQs

Check out GitHub discussion about this tool.

Authors

• Sanjiv Mathur
• Ahmad El Rouby

License

BSD 3-Clause License. See LICENSE file.