SynplifyPro and Identify

When the new attribute syn_safe_cdc is applied on a CDC path, it ensures that SynplifyPro will not add syn_preserve, syn_replicate, and syn_allow_retiming attributes, making these registers available for absorption during RAM and MATH block inference. SynplifyPro still reports the path as Safe and its description will be syn_safe_cdc attribute applied. The syn_safe_cdc can be applied on source, destination, or both. Example:

Copyreg ar /* synthesis syn_safe_cdc = 1 */;
reg zr;
reg sync;
always @(posedge clk1)
begin
    ar <= a;
end
always @(posedge clk2)
begin
    zr <= ar;
    sync <= zr;
end