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sub architecture selection

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In a block with deep asynchronous logic, there are some multiplier stages. I synthesized this block stand-alone and "report datapath" does not show me a multiplier architecture for it. Then I have applied following pragma:

assign some_prod[24:0] = {15'h0,some_term1[9:0]} * /* cadence sub_arch booth */ {{10{some_term2[14]}},some_term2[14:0]};

Please note the sign extension for the 2nd term.

Neither elab nor "synthesize -to_generic -effort high" shows me an information about this setting. The results with pragma above are without pragma are the same, ie. pragma does not seem to have an effect.

set_attr user_sub_arch booth [find / -design my_design]

does not work, because the attribute can be assigned only to subdesigns.

The reason why I do this experiment in a stand-alone synthesis is that the runtime of the complete system takes ca. 6 hours.

RC is v06.20-p003_1.

Can the HDL coding style affect the mechanism of inferring synthetic operators?


Originally posted in cdnusers.org by sporadic crash
Parents

  • Try "report datapath" after elab (need to set_attr hdl_track_filename_row_col true before elab), it will show:

    Module Instance Operator Signedness Architecture Inputs Outputs CellArea Line Col Filename
    -----------------------------------------------------------------------------------------------------------------
    mult_unsigned my_mult/mul_45_21 * unsigned very_fast/booth(u) 5x10 15 9089.71 45 21 mult.v
    -----------------------------------------------------------------------------------------------------------------


    Originally posted in cdnusers.org by synthman
Reply

  • Try "report datapath" after elab (need to set_attr hdl_track_filename_row_col true before elab), it will show:

    Module Instance Operator Signedness Architecture Inputs Outputs CellArea Line Col Filename
    -----------------------------------------------------------------------------------------------------------------
    mult_unsigned my_mult/mul_45_21 * unsigned very_fast/booth(u) 5x10 15 9089.71 45 21 mult.v
    -----------------------------------------------------------------------------------------------------------------


    Originally posted in cdnusers.org by synthman
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