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how to remove constant value flops?

tompy

 Hi :

 I got an IP from vendor. Due to design change, some part of the IP are not needed. Since it is time consuming to ask the vendor to remove those flops, I wish to do it in synthesis. I tied the unused part IP clock port and reset_n port to 0. And I want RTL compiler remove those unclocked/always reset flops.I have try set_attribute optimize_constant_0_seq true unclocke_register

but it doesn't work. Can anyone help me? thx!!

 

/tompy

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  • tompy

     Hi gh-

              after a lot of trial run, I finally find the root cause. I set boundary_opto attribute to false, which will disable constant propagation across hierarchies, thus avoid RC to remove those unused registers. After set boundary_opto to true, those registers are removed.

     

    BTW, either tied clock to 0 or tied rst_n to 0 is good enough to let RC remove thus registers.

     

    /tompy

     

Reply
  • tompy

     Hi gh-

              after a lot of trial run, I finally find the root cause. I set boundary_opto attribute to false, which will disable constant propagation across hierarchies, thus avoid RC to remove those unused registers. After set boundary_opto to true, those registers are removed.

     

    BTW, either tied clock to 0 or tied rst_n to 0 is good enough to let RC remove thus registers.

     

    /tompy

     

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