Force inference of BRAMs

[nachiket]

Is there a way to ensure only BRAMs get inferred for a particular memory object? I've tried to supply all kinds of custom commands but can't seem to get the memory $memrd_v2/write_v2 to map to anything other than FFs. I tried to supply the memory_bram pass to the script but it just says "No acceptable bram resources found."

[whitequark]

There is no way to tell Yosys to break your code. If your memory does not correspond to a valid BRAM it is an issue with how it is defined.

[nachiket]

It's a ROM. Why can't a ROM be force mapped to a BRAM?

[whitequark]

Does plain synth_xilinx, without modification, succeed?

[nachiket]

Yes, but won't map to BRAMs just a bunch of LUTs.

[whitequark]

I think on Xilinx a bunch of LUTs is actually more effective than a BRAM from a cost perspective, but try (* ram_style = "block" *) on the memory.

[nachiket]

Yup that worked, thanks! There's no way to drive this from the yosys script command without modifying the Verilog? No biggie if not.

[whitequark]

There is a setattr command that can do it from a script.