drt: allow NDR auto-taper to be disabled per net

src/OpenRoad.tcl

@@ -295,6 +295,40 @@ proc assign_ndr { args } {
   }
 }
 
+sta::define_cmd_args "set_routing_disable_auto_taper" \
+  { (-net name | -all_clocks) [-disable] [-enable] }
+
+# Per-net control of the detailed router's auto-taper behavior.  By default
+# the detailed router tapers NDR (wide) nets down to minimum width near pin
+# connections.  Some nets (e.g. wide analog/NDR traces) must keep their full
+# width all the way to the pin; use -disable to suppress auto-taper for those
+# nets without recompiling.  Use -enable to restore the default behavior.
+proc set_routing_disable_auto_taper { args } {
+  sta::parse_key_args "set_routing_disable_auto_taper" args \
+    keys {-net} flags {-all_clocks -disable -enable}
+  if { !([info exists keys(-net)] ^ [info exists flags(-all_clocks)]) } {
+    utl::error ORD 1016 "Either -net or -all_clocks need to be defined."
+  }
+  if { [info exists flags(-disable)] && [info exists flags(-enable)] } {
+    utl::error ORD 1017 "Only one of -disable or -enable may be specified."
+  }
+  # Default action is to disable auto-taper.
+  set disable [expr { ![info exists flags(-enable)] }]
+  set block [ord::get_db_block]
+  if { [info exists keys(-net)] } {
+    set netName $keys(-net)
+    set net [$block findNet $netName]
+    if { $net == "NULL" } {
+      utl::error ORD 1018 "No net named ${netName} found."
+    }
+    $net setDisableAutoTaper $disable
+  } else {
+    foreach net [sta::find_all_clk_nets] {
+      $net setDisableAutoTaper $disable
+    }
+  }
+}
+
 sta::define_cmd_args "set_debug_level" { tool group level }
 proc set_debug_level { args } {
   sta::check_argc_eq3 "set_debug_level" $args

src/drt/README.md

@@ -98,13 +98,40 @@ detailed_route
 
 #### Developer arguments
 
-Some arguments that are helpful for developers are listed here. 
+Some arguments that are helpful for developers are listed here.  
 
 | Switch Name | Description |
 | ----- | ----- |
 | `-or_seed` | Random seed for the order of nets to reroute. The default value is `-1`, and the allowed values are integers `[0, MAX_INT]`. | 
 | `-or_k` | Number of swaps is given by $k * sizeof(rerouteNets)$. The default value is `0`, and the allowed values are integers `[0, MAX_INT]`. |
 
+### Disable Auto-Taper Per Net
+
+By default the detailed router tapers non-default-rule (NDR, i.e. wide)
+nets down to minimum width near pin connections so that they fit the pin
+access geometry. For some nets (for example wide analog/NDR traces) this
+tapering is undesirable and the net must keep its full NDR width all the
+way to the pin. The following command disables auto-taper on a per-net
+basis, without recompiling. The global default behavior (auto-taper
+enabled) is unchanged for all other nets.
+
+```tcl
+set_routing_disable_auto_taper
+    (-net name | -all_clocks)
+    [-disable]
+    [-enable]
+```
+
+#### Options
+
+| Switch Name | Description |
+| ----- | ----- |
+| `-net` | Name of the net to mark. Mutually exclusive with `-all_clocks`. |
+| `-all_clocks` | Apply to all clock nets. Mutually exclusive with `-net`. |
+| `-disable` | Disable auto-taper for the selected net(s). This is the default action if neither `-disable` nor `-enable` is given. |
+| `-enable` | Re-enable auto-taper for the selected net(s), restoring the default behavior. |
+
+
 ### Detailed Route Debugging
 
 The following command and arguments are useful when debugging error

src/drt/src/db/drObj/drNet.cpp

@@ -15,6 +15,7 @@
 #include "db/obj/frBTerm.h"
 #include "db/obj/frBlockObject.h"
 #include "db/obj/frInstTerm.h"
+#include "db/obj/frNet.h"
 #include "distributed/frArchive.h"
 #include "dr/FlexDR.h"
 #include "frBaseTypes.h"
@@ -106,6 +107,11 @@ bool drNet::hasNDR() const
   return getFrNet()->getNondefaultRule() != nullptr;
 }
 
+bool drNet::autoTaperEnabled(bool global_enabled) const
+{
+  return global_enabled && !fNet_->isAutoTaperDisabled();
+}
+
 bool drNet::isClockNet() const
 {
   return fNet_->isClock();

src/drt/src/db/drObj/drNet.h

@@ -60,6 +60,10 @@ class drNet : public drBlockObject
   void clearRouteConnFigs() { routeConnFigs_.clear(); }
   frNet* getFrNet() const { return fNet_; }
   void setFrNet(frNet* net) { fNet_ = net; }
+  // True when this net should still be auto-tapered to min width near pins.
+  // Honors both the global AUTO_TAPER_NDR_NETS config and the per-net
+  // disable flag carried on the frNet.
+  bool autoTaperEnabled(bool global_enabled) const;
   const frOrderedIdSet<frBlockObject*>& getFrNetTerms() const
   {
     return fNetTerms_;

src/drt/src/db/obj/frNet.h

@@ -166,6 +166,10 @@ class frNet : public frBlockObject
   bool hasJumpers() { return has_jumpers_; }
   void setToBeDeleted(bool to_be_deleted) { to_be_deleted_ = to_be_deleted; }
   bool toBeDeleted() { return to_be_deleted_; }
+  // When true, DRT must not auto-taper this net to minimum width near pin
+  // connections (per-net override of router_cfg_->AUTO_TAPER_NDR_NETS).
+  void setDisableAutoTaper(bool in) { disable_auto_taper_ = in; }
+  bool isAutoTaperDisabled() const { return disable_auto_taper_; }
 
  protected:
   frString name_;
@@ -194,5 +198,8 @@ class frNet : public frBlockObject
   bool has_jumpers_{false};
   std::vector<frPinFig*> all_pinfigs_;
   bool to_be_deleted_{false};
+  // Per-net override: when true, auto-taper to min width near pins is
+  // suppressed for this net even if AUTO_TAPER_NDR_NETS is globally enabled.
+  bool disable_auto_taper_{false};
 };
 }  // namespace drt

src/drt/src/dr/FlexDR_maze.cpp

@@ -2229,7 +2229,7 @@ void FlexDRWorker::routeNet_prep(
     }
     unConnPins.insert(pin.get());
     if (gridGraph_.getNDR()) {
-      if (router_cfg_->AUTO_TAPER_NDR_NETS
+      if (net->autoTaperEnabled(router_cfg_->AUTO_TAPER_NDR_NETS)
           && pin->isInstPin()) {  // create a taper box for each pin
         auto [l, h] = pin->getAPBbox();
         frCoord pitch
@@ -2648,7 +2648,8 @@ void FlexDRWorker::routeNet_postAstarWritePath(
           via = net_ndr->getPrefVia(startLayerNum / 2 - 1);
         }
         auto currVia = std::make_unique<drVia>(via);
-        if (net->hasNDR() && router_cfg_->AUTO_TAPER_NDR_NETS) {
+        if (net->hasNDR()
+            && net->autoTaperEnabled(router_cfg_->AUTO_TAPER_NDR_NETS)) {
           if (isInsideTaperBox(endX, endY, startZ, endZ, mazeIdx2TaperBox)) {
             currVia->setTapered(true);
           }
@@ -2818,7 +2819,8 @@ bool FlexDRWorker::splitPathSeg(frMIdx& midX,
                                 drNet* net)
 {
   taperFirstPiece = false;
-  if (!net->hasNDR() || !router_cfg_->AUTO_TAPER_NDR_NETS) {
+  if (!net->hasNDR()
+      || !net->autoTaperEnabled(router_cfg_->AUTO_TAPER_NDR_NETS)) {
     return false;
   }
   frBox3D* bx = nullptr;

src/drt/src/io/io.cpp

@@ -1053,6 +1053,7 @@ frNet* io::Parser::addNet(odb::dbNet* db_net)
   }
   net_in->setHasJumpers(has_jumpers);
   net_in->setIsConnectedByAbutment(is_abuted);
+  net_in->setDisableAutoTaper(db_net->disableAutoTaper());
   updateNetRouting(net_in.get(), db_net);
   net_in->setType(db_net->getSigType());
   frNet* raw_net_in = net_in.get();

src/drt/src/pa/FlexPA_acc_point.cpp

@@ -1059,13 +1059,16 @@ bool FlexPA::isViaViolationFree(frAccessPoint* ap,
   design_rule_checker.setExtBox(ext_box);
   design_rule_checker.setDrcBox(ext_box);
   if (inst_term) {
-    if (!inst_term->getNet() || !inst_term->getNet()->getNondefaultRule()
-        || router_cfg_->AUTO_TAPER_NDR_NETS) {
+    auto* it_net = inst_term->getNet();
+    if (!it_net || !it_net->getNondefaultRule()
+        || (router_cfg_->AUTO_TAPER_NDR_NETS
+            && !it_net->isAutoTaperDisabled())) {
       design_rule_checker.addTargetObj(inst_term->getInst());
     }
   } else {
     if (!pin_net || !pin_net->getNondefaultRule()
-        || router_cfg_->AUTO_TAPER_NDR_NETS) {
+        || (router_cfg_->AUTO_TAPER_NDR_NETS
+            && !pin_net->isAutoTaperDisabled())) {
       design_rule_checker.addTargetObj(pin_term);
     }
   }

src/drt/src/pa/FlexPA_unique.cpp

@@ -167,6 +167,21 @@ bool UniqueInsts::isNDRInst(frInst* inst) const
   return false;
 }
 
+bool UniqueInsts::isNoAutoTaperNDRInst(frInst* inst) const
+{
+  // An instance whose pin access must be computed without auto-taper:
+  // it touches an NDR net for which tapering is suppressed, either
+  // globally (!AUTO_TAPER_NDR_NETS) or per-net (disable_auto_taper).
+  for (const auto& a : inst->getInstTerms()) {
+    auto* net = a->getNet();
+    if (net && net->getNondefaultRule()
+        && (!router_cfg_->AUTO_TAPER_NDR_NETS || net->isAutoTaperDisabled())) {
+      return true;
+    }
+  }
+  return false;
+}
+
 UniqueClassKey UniqueInsts::computeUniqueClassKey(frInst* inst) const
 {
   const odb::Point origin = inst->getOrigin();
@@ -196,7 +211,7 @@ UniqueClassKey UniqueInsts::computeUniqueClassKey(frInst* inst) const
   }
   // Special case for NDR instances, create a separate unique class for them
   frInst* ndr_inst = nullptr;
-  if (!router_cfg_->AUTO_TAPER_NDR_NETS && isNDRInst(inst)) {
+  if (isNoAutoTaperNDRInst(inst)) {
     ndr_inst = inst;
   }
   std::set<frTerm*> stubborn_terms;

src/drt/src/pa/FlexPA_unique.h

@@ -193,6 +193,7 @@ class UniqueInsts
    * terminal.
    */
   bool isNDRInst(frInst* inst) const;
+  bool isNoAutoTaperNDRInst(frInst* inst) const;
   bool hasTrackPattern(frTrackPattern* tp, const odb::Rect& box) const;
 
   /**

src/drt/test/BUILD

@@ -18,6 +18,7 @@ COMPULSORY_TESTS = [
     "ndr_vias1",
     "ndr_vias2",
     "ndr_vias3",
+    "ndr_no_auto_taper",
     "obstruction",
     "single_step",
     "ta_ap_aligned",
@@ -36,6 +37,7 @@ ALL_TESTS = COMPULSORY_TESTS + PASSFAIL_TESTS
 BIG_TESTS = [
     "ndr_vias1",
     "ndr_vias2",
+    "ndr_no_auto_taper",
 ]
 
 PY_TESTS = [

src/drt/test/CMakeLists.txt

@@ -8,6 +8,7 @@ or_integration_tests(
     ndr_vias1
     ndr_vias2
     ndr_vias3
+    ndr_no_auto_taper
     obstruction
     single_step
     ta_ap_aligned
@@ -22,5 +23,6 @@ or_integration_tests(
 set_tests_properties(
   drt.ndr_vias1.tcl
   drt.ndr_vias2.tcl
+  drt.ndr_no_auto_taper.tcl
   PROPERTIES TIMEOUT 900
 )