#1112 Add clock tree metal layer constraints Issue created by antonblanchard @jjcherry56 points out that Openlane is not constraining the clock tree metal layers. Depending on the process, we might want to use upper/larger metal layers. We need a few changes: 1. Environment variables in open_pdks for the clock min/max layers. open_pdks does have:

set ::env(CLOCK_WIRE_RC_LAYER) "met5"

However met5 seems a bit of an odd setting. We really want variables for min and max layers (eg met3-met5).

CLOCK_MIN_LAYER/CLOCK_MAX_LAYER

perhaps? 2. Telling global routing the layers to use (remembering to cap the max layer if we are taping out a macro):

set_routing_layers -clock $::env(CLOCK_MIN_LAYER)-$::env(CLOCK_MAX_LAYER)

3. Telling STA what layer to use for RC estimates:

set_wire_rc -clock -layer $::env(CLOCK_MIN_LAYER)

The-OpenROAD-Project/OpenLane