[Synth] Support MIG lowering in CombToAIG conversion pass #8932
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This patch extends the synthesis pipeline to support lowering combinational operations to Majority-Inverter Graphs (MIG) in addition to And-Inverter Graphs (AIG). The implementation adds a CombToSynthTarget enum with AIG/MIG options, implements MIG-specific conversion patterns for OR operations using majority functions, updates adder carry logic to use majority functions in MIG mode, and renames the pipeline from AIGLowering to CombLowering to reflect the generalized capability. The MIG representation uses 3-input majority functions (MAJ(a,b,c) = a&b | a&c | b&c) which are more efficient than AIG for arithmetic operations. Integration tests verify functional equivalence using circt-lec.
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fabianschuiki
approved these changes
Sep 8, 2025
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This patch extends the synthesis pipeline to support lowering combinational operations to Majority-Inverter Graphs (MIG) in addition to And-Inverter Graphs (AIG). The implementation adds a CombToAIGTarget enum with AIG/MIG options, implements MIG-specific conversion patterns for OR operations using majority functions, updates adder carry logic to use majority functions in MIG mode, and renames the pipeline from AIGLowering to CombLowering to reflect the generalized capability. Integration tests verify functional equivalence using circt-lec.
In the follow-up I'm planning to rename CombToAIG to CombToSynth so reflect the pass can lower IR to both AIG and MIG.