How do hierarchy and BLOCK flows work?

[TanjIsGray]

I have a design which uses multiples of 4 blocks or macros which were designed to be individually optimized and then placed by abutment. I can get pretty decent runs on one block at a time but when I try to use the blocks in the whole design all that comes out is the first listed block.

Looking through examples I see similar behavior with AES (using asap7). Visualizing the layout result does evidence hierarchy with fuzzy clouds for the repeated blocks, but they are not clearly defined macros using the block design. If aes-block is run it generates a nice compact aes_rcon but ignores aes_sbox, and that is all it generates. One block, not a whole AES pipe.

Any hints why I see no blocks incorporated in the aes project, and only one lone block in aes-block with everything else missing?

Thank you in advance.

[maliberty]

The idea is that BLOCKs will be run separately and hardened for use in the top level. That's what makes the flow hierarchical. aes_blocks is just a small/fast demonstration of a hierarchical flow. Such a design is too small to really need such a flow. You can see a bigger design like asap7/mock-array for a more interesting example.

[TanjIsGray]

Thank-you. Yes I have run mock-array too, but that has the same behavior. I just end up with a single mock-array_Element result in asap7, can't figure out how to build a multi-Element array.

I did make verilog, then make, with these in settings.mk:

export MOCK_ARRAY_TABLE = 4 4 5 6 8 6
export MOCK_ARRAY_DATAWIDTH = 4
export DESIGN_CONFIG=designs/asap7/mock-array/config.mk

I can't find any hints on how to make a whole array.

I'll just fall back to SYNTH_HIERARCHICAL for my own project and see how good that might be.

[maliberty]

How are you running it?

[TanjIsGray]

I am running on Ubuntu 22.04 LTS, fully updated. No containers, it is a dedicated machine.

Chisel did not come with OR, so I installed with instructions here: https://github.com/chipsalliance/chisel/blob/main/SETUP.md

I followed the instructions in flow/designs/asap7/mock-array/README.md, placing the exports in settings.mk and then running
$ make verilog
$ make

Presumably I left something out? those two steps appeared to finish normally, and the resulting Element looks nice. Just lonely.

[maliberty]

If you look in flow/logs/asap7 do you see mock-array and mock-array_Element subdirs?

[TanjIsGray]

Sorry for delay .. my day job, and currently reinstalling OpenROAD to be sure there is no issue there. Will be back with that answer soon.

[TanjIsGray]

I had some problem with directories owned by root - probably too much use of sudo somewhere in the build process. So I deleted OR directories and built again from scratch, including running the basic tests..

asap7/mock-array builds only mock_array_Element (in logs, reports, and results).
How should I build the whole array? I have edited nothing except to select the project in flow/makefile.

asap7/aes builds the whole pipe with no hierarchy.
asap7/aes-block builds only aes-block_aes_rcon (logs, reports, results) even though the config lists aes_sbox as well. And there is no whole pipe using any blocks.

[maliberty]

What you describe is not what I or the CI sees. It sounds like a local problem in your setup. There is no separate step required to build the top. I suggests you make a clean area and try again. If it persists then open a issue with full details.

[TanjIsGray]

OK, thanks for looking.

I found what I was doing wrong with mock-array. The settings used for "make verilog" must NOT be used for the "make".

So, that gives me a useful example to study.