peepopt - collection of peephole optimizers

yosys> help peepopt

peepopt [options] [selection]

This pass applies a collection of peephole optimizers to the current design.

This pass employs the following rules by default:

   * muldiv - Replace (A*B)/B with A

   * shiftmul - Replace A>>(B*C) with A'>>(B<<K) where C and K are constants
                and A' is derived from A by appropriately inserting padding
                into the signal. (right variant)

                Analogously, replace A<<(B*C) with appropriate selection of
                output bits from A<<(B<<K). (left variant)

   * shiftadd - Replace A>>(B+D) with (A'>>D)>>(B) where D is constant and
                A' is derived from A by padding or cutting inaccessible bits.
                Scratchpad: 'peepopt.shiftadd.max_data_multiple' (default: 2)
                limits the amount of padding to a multiple of the data,
                to avoid high resource usage from large temporary MUX trees.

If -formalclk is specified it instead employs the following rules:

   * clockgateff - Replace latch based clock gating patterns with a flip-flop
                   based pattern to prevent combinational paths from the
                   output to the enable input after running clk2fflogic.