unable to understand Synplicity pro warning

[s3034585]

pruning register synplicity

Hi Guys
I am using synplicify pro 7.7 for synthesis. While synthesis i am getting a warning as follows:
@W: CL169: mycode.vhd(177): Pruning Register rslt_req_ff(1)

I tried to search this on net but didnt get any info on it. Can any one please tell me about it.

Thanks in advance
tama

 

[nand_gates]

pruning register warning

Can you post ur code here??

 

[sree205]

i believe that the register in question is redundant and the tool has either removed or multiplexed it with some other register.

 

[altair_06]

Hi,

This warning occurs when the compiler or mapper detects a register fixed at a constant value, either through optimization or through constant propagation, and then removes it. In your case the register bit rslt_req_ff(1) must have been fixed at a constant value. Hence you can avoid the warning message by using the directive "syn_preserve" for the specific register. [i.e /*synthesis syn_preserve=1 */ ]