Circular dependency with ppl and mpl2

[donn]

The -skip_io option for ppl allows the pin placer to incorporate preliminary global placement info: #3962 (comment)

Because of this, in our flow, we have this dependency chain:

• ppl requires global placement with skipio
• global placement with skipio requires rows to be cut to avoid macros
• rows being cut requires macros placed
• macros are placed at manual co-ordinates

Attempting to introduce mpl2 transforms it into an ouroboros:

• mpl2 requires pins to be placed
• ppl requires global placement with skipio
• global placement with skipio requires rows to be cut to avoid macros
• rows being cut requires macros placed
• macros are placed using mpl2

There are a couple ways to break this chain:

• Running GlobalPlacement with skipio with the full floorplan
  • This causes the subsequent GlobalPlacement to fail as there will be instances placed on top of macros and global placement will not be able to move them to a nearby site
• Requiring manual pin placement to use mpl2
• Disabling skipio global placement (and thus that whole pin placement flow) if there are any unplaced macros

What do you guys recommend?

[donn]

Ended up using the first chain-breaker and just doing this after pin placement

set ::db [::ord::get_db]
set ::chip [$::db getChip]
set ::tech [$::db getTech]
set ::block [$::chip getBlock]
set ::insts [$::block getInsts]
foreach inst $::insts {
    $inst setPlacementStatus "NONE"
}