feat!: allow PDKs without diode, antenna, and/or decap cells

Some PDKs have self-tapping standard cells, do not suffer from the antenna effect, have no endcap cell, or a combination of those.

This patch makes the variables options and modifies included steps to no longer assume their existence.

Changelog.md

@@ -28,6 +28,11 @@
   * `PDN_OBSTRUCTIONS` and `ROUTING_OBSTRUCTIONS` are now lists of tuples
     instead of variable-length Tcl-style lists (AKA: strings).
 
+* `Odb.DiodesOnPorts`, `Odb.PortDiodePlacement`, `Odb.FuzzyDiodePlacement`,
+  `Odb.HeuristicDiodeInsertion`
+
+  * Steps no longer assume `DIODE_CELL` exists and fall back to doing nothing.
+
 * `OpenROAD.*`
 
   * Added `PNR_CORNERS`. An override for `DEFAULT_CORNER` for PnR steps except
@@ -65,8 +70,8 @@
   * Added `DRT_SAVE_SNAPSHOTS` which enables saving snapshots of the layout each
     detalied routing iteration.
   * Added `DRT_SAVE_DRC_REPORT_ITERS`
-  * Added `DRT_ANTENNA_REPAIR_ITERS`, which if greater than zero, enables
-    antenna fixing after detailed routing
+  * Added `DRT_ANTENNA_REPAIR_ITERS`, which, if greater than zero and
+    `DIODE_CELL` is set, enables antenna fixing after detailed routing
   * Added `DRT_ANTENNA_MARGIN` which is similar to `GRT_ANTENNA_MARGIN` but for
     the aforementioned antenna repair iterations
 
@@ -81,6 +86,10 @@
 
   * Corrected `GPL_CELL_PADDING` to be an integer.
 
+* `OpenROAD.RepairAntennas`
+
+  * Step no longer assumes `DIODE_CELL` exists and falls back to doing nothing.
+
 * `OpenROAD.RepairDesignPostGPL`
 
   * Added optional variable `DESIGN_REPAIR_MAX_UTIL_PCT`
@@ -115,6 +124,11 @@
     * `GRT_RESIZER_HOLD_REPAIR_TNS_PCT`
     * `GRT_RESIZER_HOLD_MAX_UTIL_PCT`
 
+* `OpenROAD.TapDecapInsertion`
+
+  * No longer assumes `WELLTAP_CELL` has a value and skips tap insertion if not.
+  * No longer assumes `DECAP_CELL` has a value and skips decap insertion if not.
+
 * Created `OpenROAD.UnplaceAll`
 
   * Removes the placement status of all instances.
@@ -208,6 +222,7 @@
 
   * `{GPL,DPL}_CELL_PADDING`, `PL_MAX_DISPLACEMENT_{X,Y}` now all integers to
     match OpenROAD.
+  * `WELLTAP_CELL`, `DECAP_CELL` now optional.
 
 * `Checker.HoldViolations`
 

openlane/config/flow.py

@@ -304,20 +304,6 @@ def _prefix_to_wildcard(prefixes_raw: Union[str, Sequence[str]]):
         "Defines a buffer port to be used by yosys during synthesis: in the format `{cell}/{input_port}/{output_port}`",
         pdk=True,
     ),
-    Variable(
-        "WELLTAP_CELL",
-        str,
-        "Defines the cell used for tap insertion.",
-        pdk=True,
-        deprecated_names=["FP_WELLTAP_CELL"],
-    ),
-    Variable(
-        "ENDCAP_CELL",
-        str,
-        "Defines the so-called 'end-cap' cell- class of decap cells placed at either sides of a design.",
-        pdk=True,
-        deprecated_names=["FP_ENDCAP_CELL"],
-    ),
     # Placement
     Variable(
         "PLACE_SITE",
@@ -335,9 +321,23 @@ def _prefix_to_wildcard(prefixes_raw: Union[str, Sequence[str]]):
     Variable(
         "DIODE_CELL",
         Optional[str],
-        "Defines a diode cell used to fix antenna violations, in the format {name}/{port}.",
+        "Defines a diode cell used to fix antenna violations, in the format {name}/{port}. If not defined, steps should not attempt to repair the antenna effect by inserting diode cells.",
         pdk=True,
     ),
+    Variable(
+        "WELLTAP_CELL",
+        Optional[str],
+        "Defines the cell used for tap insertion. If not defined, steps should not attempt to insert welltap cells.",
+        pdk=True,
+        deprecated_names=["FP_WELLTAP_CELL"],
+    ),
+    Variable(
+        "ENDCAP_CELL",
+        Optional[str],
+        "Defines the so-called 'end-cap' cell- class of decap cells placed at either sides of a design, if available.",
+        pdk=True,
+        deprecated_names=["FP_ENDCAP_CELL"],
+    ),
 ]
 option_variables = [
     # Common

openlane/scripts/openroad/cut_rows.tcl

@@ -15,12 +15,10 @@ source $::env(SCRIPTS_DIR)/openroad/common/io.tcl
 read_current_odb
 
 set arg_list [list]
-lappend arg_list -endcap_master $::env(ENDCAP_CELL)
 lappend arg_list -halo_width_x $::env(FP_MACRO_HORIZONTAL_HALO)
 lappend arg_list -halo_width_y $::env(FP_MACRO_VERTICAL_HALO)
-if { [info exists ::env(FP_PRUNE_THRESHOLD)] } {
-    lappend arg_list -row_min_width $::env(FP_PRUNE_THRESHOLD)
-}
+append_if_exists_argument arg_list FP_PRUNE_THRESHOLD -row_min_width
+append_if_exists_argument arg_list ENDCAP_CELL -endcap_master
 log_cmd cut_rows {*}$arg_list
 
 # # verify -row_min_width worked

openlane/scripts/openroad/drt.tcl

@@ -66,17 +66,23 @@ drt_run $i {*}$drt_args
 
 incr i
 
-set diode_cell [lindex [split $::env(DIODE_CELL) "/"] 0]
+if { ![info exists ::env(DIODE_CELL)] } {
+    puts "\[INFO\] Skipping post-DRT antenna repair: DIODE_CELL not set."
+} elseif { $::env(DRT_ANTENNA_REPAIR_ITERS) == 0 } {
+    puts "\[INFO\] Skipping post-DRT antenna repair: DRT_ANTENNA_REPAIR_ITERS set to 0."
+} else {
+    set diode_cell [lindex [split $::env(DIODE_CELL) "/"] 0]
 
-while {$i <= $::env(DRT_ANTENNA_REPAIR_ITERS) && [log_cmd check_antennas]} {
-    puts "\[INFO\] Running antenna repair iteration $i…"
-    set diodes_inserted [log_cmd repair_antennas $diode_cell -ratio_margin $::env(DRT_ANTENNA_MARGIN)]
-    if {$diodes_inserted} {
-        drt_run $i {*}$drt_args
-    } else {
-        puts "\[INFO\] No diodes inserted. Ending antenna repair iterations."
-        break
+    while {$i <= $::env(DRT_ANTENNA_REPAIR_ITERS) && [log_cmd check_antennas]} {
+        puts "\[INFO\] Running antenna repair iteration $i…"
+        set diodes_inserted [log_cmd repair_antennas $diode_cell -ratio_margin $::env(DRT_ANTENNA_MARGIN)]
+        if {$diodes_inserted} {
+            drt_run $i {*}$drt_args
+        } else {
+            puts "\[INFO\] No diodes inserted. Ending antenna repair iterations."
+            break
+        }
+        incr i
     }
-    incr i
 }
 write_views

openlane/scripts/openroad/tapcell.tcl

@@ -14,12 +14,19 @@
 source $::env(SCRIPTS_DIR)/openroad/common/io.tcl
 read_current_odb
 
-log_cmd tapcell\
-    -distance $::env(FP_TAPCELL_DIST)\
-    -tapcell_master "$::env(WELLTAP_CELL)"\
-    -endcap_master "$::env(ENDCAP_CELL)"\
-    -halo_width_x $::env(FP_MACRO_HORIZONTAL_HALO)\
-    -halo_width_y $::env(FP_MACRO_VERTICAL_HALO)
+set tapcell_args [list]
+append_if_exists_argument tapcell_args FP_TAPCELL_DIST -distance
+append_if_exists_argument tapcell_args WELLTAP_CELL -tapcell_master
+append_if_exists_argument tapcell_args ENDCAP_CELL -endcap_master
 
+if { [llength tapcell_args] } {
+    log_cmd tapcell\
+        -halo_width_x $::env(FP_MACRO_HORIZONTAL_HALO)\
+        -halo_width_y $::env(FP_MACRO_VERTICAL_HALO)\
+        {*}$tapcell_args
+
+} else {
+    puts "\[INFO\] WELLTAP_CELL and ENDCAP_CELL both unspecified. Doing nothing."
+}
 
 write_views

openlane/steps/odb.py

@@ -718,6 +718,10 @@ def run(self, state_in: State, **kwargs) -> Tuple[ViewsUpdate, MetricsUpdate]:
             info("'DIODE_ON_PORTS' is set to 'none': skipping…")
             return {}, {}
 
+        if self.config["DIODE_CELL"] is None:
+            info("DIODE_CELL not set. Skipping…")
+            return {}, {}
+
         if self.config["GPL_CELL_PADDING"] == 0:
             self.warn(
                 "'GPL_CELL_PADDING' is set to 0. This step may cause overlap failures."
@@ -757,6 +761,9 @@ def run(self, state_in: State, **kwargs) -> Tuple[ViewsUpdate, MetricsUpdate]:
         if self.config["DIODE_ON_PORTS"] == "none":
             info("'DIODE_ON_PORTS' is set to 'none': skipping…")
             return {}, {}
+        if self.config["DIODE_CELL"] is None:
+            info("DIODE_CELL not set. Skipping…")
+            return {}, {}
         return super().run(state_in, **kwargs)
 
 
@@ -826,6 +833,10 @@ def run(self, state_in: State, **kwargs) -> Tuple[ViewsUpdate, MetricsUpdate]:
                 "'GPL_CELL_PADDING' is set to 0. This step may cause overlap failures."
             )
 
+        if self.config["DIODE_CELL"] is None:
+            info("DIODE_CELL not set. Skipping…")
+            return {}, {}
+
         return super().run(state_in, **kwargs)
 
 
@@ -860,6 +871,12 @@ class HeuristicDiodeInsertion(CompositeStep):
         GlobalRouting,
     ]
 
+    def run(self, state_in: State, **kwargs) -> Tuple[ViewsUpdate, MetricsUpdate]:
+        if self.config["DIODE_CELL"] is None:
+            info("DIODE_CELL not set. Skipping…")
+            return {}, {}
+        return super().run(state_in, **kwargs)
+
 
 @Step.factory.register()
 class CellFrequencyTables(OdbpyStep):

openlane/steps/openroad.py

@@ -1181,6 +1181,13 @@ class TapEndcapInsertion(OpenROADStep):
     name = "Tap/Decap Insertion"
 
     config_vars = OpenROADStep.config_vars + [
+        Variable(
+            "FP_TAPCELL_DIST",
+            Optional[Decimal],
+            "The distance between tap cell columns. Must be specified if WELLTAP_CELL is specified.",
+            units="µm",
+            pdk=True,
+        ),
         Variable(
             "FP_MACRO_HORIZONTAL_HALO",
             Decimal,
@@ -1197,18 +1204,19 @@ class TapEndcapInsertion(OpenROADStep):
             units="µm",
             deprecated_names=["FP_TAP_VERTICAL_HALO"],
         ),
-        Variable(
-            "FP_TAPCELL_DIST",
-            Decimal,
-            "The distance between tap cell columns.",
-            units="µm",
-            pdk=True,
-        ),
     ]
 
     def get_script_path(self):
         return os.path.join(get_script_dir(), "openroad", "tapcell.tcl")
 
+    def run(self, state_in, **kwargs):
+        if (
+            self.config["WELLTAP_CELL"] is not None
+            and self.config["FP_TAPCELL_DIST"] is None
+        ):
+            raise StepException("FP_TAPCELL_DIST must be set if WELLTAP_CELL is set.")
+        return super().run(state_in, **kwargs)
+
 
 @Step.factory.register()
 class UnplaceAll(OpenROADStep):
@@ -1663,6 +1671,13 @@ class RepairAntennas(CompositeStep):
 
     Steps = [_DiodeInsertion, CheckAntennas]
 
+    def run(self, state_in: State, **kwargs) -> Tuple[ViewsUpdate, MetricsUpdate]:
+        if self.config["DIODE_CELL"] is None:
+            info("DIODE_CELL not set. Skipping…")
+            return {}, {}
+
+        return super().run(state_in, **kwargs)
+
 
 @Step.factory.register()
 class DetailedRouting(OpenROADStep):