[Synth] LowerWordsToBits: Improve scalability with bit-sensitive constprop #8997
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…prop Previously, GreedyPatternRewriter was naively used to bit-blast multi-bit values but it didn't scale well due to worklist iteration and unnecessary IR creation which occasionally ended up with constant values. Hence the pass was often not scalable for large designs. This commit fixes the issue by applying constant propagation during the bit-blast process and replaces GreedyPatternRewriter with a manual one-shot walk with recursion. Key improvements: - Rename Driver class to BitBlaster for better clarity - Complete rewrite from pattern-based approach to sophisticated algorithm - Implement known bits analysis for efficient constant propagation - Add comprehensive statistics collection and performance metrics - Enhance bit extraction logic with intelligent caching mechanisms - Support full range of operations: AIG, MIG, and combinatorial ops - Improve error handling with combinational cycle detection - Preserve debugging information with name hint propagation The new implementation provides significant scalability improvements through bit-sensitive constant propagation, enabling more efficient synthesis of large multi-bit operations by avoiding unnecessary computations on constant bits.
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Previously, GreedyPatternRewriter was naively used to bit-blast multi-bit values but it didn't scale well due to worklist iteration and unnecessary IR creation which occasionally ended up with constant values. Hence the pass was often not scalable for large designs.
This commit fixes the issue by applying constant propagation during the bit-blast process and replaces GreedyPatternRewriter with a manual one-shot walk with recursion.