this limited ports to 16384, which seemed reasonable at the time.
However, the sky130_sram_macro layouts connect power and ground in a
way that when coupled with "extract unique" can generate tens of
thousands of ports and overrun the bit field, showing that automation
can do the unexpected. The solution was to split out the port number
from the label record as its own 32-bit value.
an optional extra argument to the "select" command that can be used
to select labels by glob-style matching; e.g., "select area labels
VSS*" or "select less area labels *_1". This will help in managing
labels after flattening a standard cell design; e.g., by using
"select less area labels */VDD".
Tim Edwards