llvm / llvm/circt

[Synth] Enhance 3-input logic operations

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#10,407 2 comments 0 reactions 1 assignee View on GitHub

@okekayode is already working on this.

Since May 7, 2026.

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Description

Look at https://si2.epfl.ch/~demichel/publications/archive/2021/3Input.pdf, and introduce following operations that look useful.

```
synth.onehot (n input)
synth.mux_inv (3 input)
synth.majority (2*n+1 input)
```
Note that `synth.majority` is re-introduction of `synth.mig.maj_inv` but this time
the operation is simply one of 3-input logic operations, and is not considered as a primary target of homogeneous logic representation. So three shouldn't be no concern from the patent perspective (see https://github.com/llvm/circt/issues/10152). Though we have to make sure not to introduce mig specific optimizations (specifically algebraic rewriting etc).

The addition of these operations can be done in a declarative way using BooleanLogicOpInterface.

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