| 摘要 |
A large block synthesis (LBS) process pre-optimizes selected submacros by synthesizing the submacros using timing assertions and placement abstracts, removing placement information, and assigning weights to the internal nets of the submacros that are much higher than weights used for external (e.g., top-level) nets. The timing assertions include an input arrival time, a required output arrival time, and an output pin capacitance loading for the logic block, and the placement abstract is generated by condensing input and output pins of the logic block at a center of gravity of the logic block. The submacros to be pre-optimized can automatically be identified using an attribute to indicate pre-optimization, or by determining that the submacro is one of many instances in the design. The higher weights for the submacro nets define soft-bounds for the logic which still allow relocation of submacro components. The pre-optimization results in significantly reduced synthesis runtime.
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