Adjust keep_hierarchy behavior
#4706
Conversation
|
There's still a bit of a disconnect with the |
When I built this I experimented with also running opt in the flow and it didn't make much of a difference vs just techmapping, so I think this may not be as much of a problem? Anyway, it's just a knob for the user to twiddle, and users with an engineering background (the core audience) usually like that kind of arbitrary control, even if to a fault |
|
For instance numbers I expect opt isn’t as important as the abc transformations and mapping to technology cells |
| @@ -23,20 +23,77 @@ | |||
| USING_YOSYS_NAMESPACE | |||
| PRIVATE_NAMESPACE_BEGIN | |||
|
|
|||
| struct ThresholdHiearchyKeeping { | |||
There was a problem hiding this comment.
nit: Hiearchy -> Hierarchy
| @@ -575,6 +575,9 @@ Non-standard or SystemVerilog features for formal verification | |||
| ``@(posedge <netname>)`` or ``@(negedge <netname>)`` when ``<netname>`` | |||
| is marked with the ``(* gclk *)`` Verilog attribute. | |||
|
|
|||
| - The `gate_cost_equivalent` attribute on a module can be used to specify | |||
There was a problem hiding this comment.
This chapter is "Non-standard or SystemVerilog features for formal verification", shouldn't it go into the preceding one?
There was a problem hiding this comment.
Maybe we could direct readers to check the keep_hierarchy help string?
| log(" gates after simple techmapping. Intended for tuning trade-offs between\n"); | ||
| log(" quality and yosys runtime.\n"); | ||
| log("\n"); | ||
| log(" When evaluating a module's cost, gates which are within a submodule\n"); |
There was a problem hiding this comment.
It seems like modules already labeled keep_hierarchy before this pass would still contribute to their supermodule's sum cost
What are the reasons/motivation for this change?
This makes two changes to
keep_hierarchy -min_costto make it better suited to the task of partially preserving hierarchy for macro placement:keep_hierarchytowards the upper module's cost.gate_cost_equivalentattribute as a way of specifying cost on blackboxes.