rsz: use adequate buffers for each operation

src/rsz/include/rsz/Resizer.hh

@@ -712,6 +712,7 @@ class Resizer : public dbStaState
   int inserted_buffer_count_ = 0;
   int cloned_gate_count_ = 0;
   int removed_buffer_count_ = 0;
+  bool exclude_clock_buffers_ = true;
   bool buffer_moved_into_core_ = false;
   // Slack map variables.
   // This is the minimum length of wire that is worth while to split and

src/rsz/src/Resizer.cc

@@ -58,6 +58,7 @@
 #include "sta/Liberty.hh"
 #include "sta/Network.hh"
 #include "sta/Parasitics.hh"
+#include "sta/PatternMatch.hh"
 #include "sta/PortDirection.hh"
 #include "sta/Sdc.hh"
 #include "sta/Search.hh"
@@ -501,14 +502,34 @@ void Resizer::findBuffers()
 {
   if (buffer_cells_.empty()) {
     LibertyLibraryIterator* lib_iter = network_->libertyLibraryIterator();
+    std::unique_ptr<sta::PatternMatch> clkbuf_pattern;
+
+    if (exclude_clock_buffers_) {
+      clkbuf_pattern
+          = std::make_unique<sta::PatternMatch>(".*CLKBUF.*",
+                                                /* is_regexp */ true,
+                                                /* nocase */ true,
+                                                /* Tcl_interp* */ nullptr);
+    }
+
     while (lib_iter->hasNext()) {
       LibertyLibrary* lib = lib_iter->next();
+
       for (LibertyCell* buffer : *lib->buffers()) {
+        if (exclude_clock_buffers_) {
+          // is_clock_cell is a custom lib attribute that may not exist,
+          // so we also use the name pattern to help
+          if (buffer->isClockCell() || clkbuf_pattern->match(buffer->name())) {
+            continue;
+          }
+        }
+
         if (!dontUse(buffer) && isLinkCell(buffer)) {
           buffer_cells_.emplace_back(buffer);
         }
       }
     }
+
     delete lib_iter;
 
     if (buffer_cells_.empty()) {
@@ -519,6 +540,7 @@ void Resizer::findBuffers()
              return bufferDriveResistance(buffer1)
                     > bufferDriveResistance(buffer2);
            });
+
       buffer_lowest_drive_ = buffer_cells_[0];
     }
   }
@@ -2811,6 +2833,14 @@ void Resizer::repairHold(
     int max_passes,
     bool verbose)
 {
+  buffer_cells_.clear();
+
+  // Some technologies such as nangate45 don't have delay cells. Hence,
+  // until we have a better approach, it's better to consider clock buffers
+  // for hold violation repairing as these buffers' delay may be slighty
+  // higher and we'll need fewer insertions.
+  exclude_clock_buffers_ = false;
+
   resizePreamble();
   if (parasitics_src_ == ParasiticsSrc::global_routing) {
     opendp_->initMacrosAndGrid();
@@ -2821,6 +2851,10 @@ void Resizer::repairHold(
                            max_buffer_percent,
                            max_passes,
                            verbose);
+
+  // Reset buffer selection strategy for the subsequent RSZ operation.
+  exclude_clock_buffers_ = true;
+  buffer_cells_.clear();
 }
 
 void Resizer::repairHold(const Pin* end_pin,
@@ -2830,13 +2864,22 @@ void Resizer::repairHold(const Pin* end_pin,
                          float max_buffer_percent,
                          int max_passes)
 {
+  buffer_cells_.clear();
+
+  // See comments on previous method.
+  exclude_clock_buffers_ = false;
+
   resizePreamble();
   repair_hold_->repairHold(end_pin,
                            setup_margin,
                            hold_margin,
                            allow_setup_violations,
                            max_buffer_percent,
                            max_passes);
+
+  // Ditto.
+  exclude_clock_buffers_ = true;
+  buffer_cells_.clear();
 }
 
 int Resizer::holdBufferCount() const

src/rsz/test/buffer_ports4.ok

@@ -11,7 +11,7 @@ Pin                                    Limit    Slew   Slack
 ------------------------------------------------------------
 input1/Z                                0.20    1.15   -0.95 (VIOLATED)
 
-[INFO RSZ-0058] Using max wire length 828um.
+[INFO RSZ-0058] Using max wire length 833um.
 [INFO RSZ-0039] Resized 1 instances.
 max slew
 

src/rsz/test/buffer_varying_lengths.ok

@@ -1,15 +1,15 @@
 [INFO ODB-0227] LEF file: Nangate45/Nangate45.lef, created 22 layers, 27 vias, 135 library cells
-[INFO RSZ-0058] Using max wire length 822um.
+[INFO RSZ-0058] Using max wire length 827um.
 [INFO RSZ-0037] Found 118 long wires.
-[INFO RSZ-0038] Inserted 162 buffers in 118 nets.
-[INFO RSZ-0039] Resized 183 instances.
+[INFO RSZ-0038] Inserted 161 buffers in 118 nets.
+[INFO RSZ-0039] Resized 184 instances.
 worst slack -0.266
-tns -28.587
+tns -28.551
 [INFO RSZ-0094] Found 200 endpoints with setup violations.
 [INFO RSZ-0099] Repairing 200 out of 200 (100.00%) violating endpoints...
-[INFO RSZ-0041] Resized 895 instances.
+[INFO RSZ-0041] Resized 844 instances.
 [WARNING RSZ-0062] Unable to repair all setup violations.
 [INFO RSZ-0033] No hold violations found.
 worst slack -0.266
-tns -27.381
+tns -27.434
 No differences found.

src/rsz/test/gcd_resize.ok

@@ -7,17 +7,17 @@
 worst slack 1.34
 [INFO RSZ-0028] Inserted 18 output buffers.
 [INFO RSZ-0058] Using max wire length 693um.
-[INFO RSZ-0039] Resized 50 instances.
+[INFO RSZ-0039] Resized 58 instances.
 [INFO RSZ-0098] No setup violations found
 [INFO RSZ-0046] Found 35 endpoints with hold violations.
-[INFO RSZ-0032] Inserted 99 hold buffers.
+[INFO RSZ-0032] Inserted 105 hold buffers.
 worst slack 0.20
-worst slack 1.24
+worst slack 1.25
 max slew
 
 Pin                                    Limit    Slew   Slack
 ------------------------------------------------------------
-_443_/ZN                                0.20    0.06    0.14 (MET)
+_443_/ZN                                0.20    0.04    0.15 (MET)
 
 max fanout
 
@@ -29,7 +29,7 @@ max capacitance
 
 Pin                                    Limit     Cap   Slack
 ------------------------------------------------------------
-_443_/ZN                               10.47    3.86    6.62 (MET)
+_448_/ZN                               10.47    1.92    8.55 (MET)
 
 Driver    length delay
 _759_/Z manhtn 83.9 steiner 83.9 0.00
@@ -43,4 +43,4 @@ _461_/Z manhtn 63.8 steiner 84.8 0.00
 req_msg[18] manhtn 61.4 steiner 61.4 0.00
 _847_/Z manhtn 60.3 steiner 60.3 0.00
 _851_/Z manhtn 58.3 steiner 58.3 0.00
-Design area 756 u^2 12% utilization.
+Design area 772 u^2 12% utilization.

src/rsz/test/repair_cap3.ok

@@ -7,7 +7,7 @@
 [INFO ODB-0133]     Created 2 nets and 105 connections.
 Found 105 slew violations
 Found 1 cap violations
-[INFO RSZ-0058] Using max wire length 2393um.
+[INFO RSZ-0058] Using max wire length 2406um.
 [INFO RSZ-0034] Found 1 slew violations.
 [INFO RSZ-0036] Found 1 capacitance violations.
 [INFO RSZ-0038] Inserted 2 buffers in 1 nets.

src/rsz/test/repair_design2.ok

@@ -5,5 +5,5 @@
 [INFO ODB-0131]     Created 3 components and 14 component-terminals.
 [INFO ODB-0132]     Created 2 special nets and 0 connections.
 [INFO ODB-0133]     Created 4 nets and 6 connections.
-[INFO RSZ-0058] Using max wire length 2393um.
+[INFO RSZ-0058] Using max wire length 2406um.
 [INFO RSZ-0039] Resized 3 instances.

src/rsz/test/repair_design3.ok

@@ -5,5 +5,5 @@
 [INFO ODB-0131]     Created 1001 components and 5004 component-terminals.
 [INFO ODB-0132]     Created 2 special nets and 0 connections.
 [INFO ODB-0133]     Created 2 nets and 1001 connections.
-[INFO RSZ-0058] Using max wire length 2393um.
+[INFO RSZ-0058] Using max wire length 2406um.
 [INFO RSZ-0039] Resized 1000 instances.

src/rsz/test/repair_design3_verbose.ok

@@ -5,7 +5,7 @@
 [INFO ODB-0131]     Created 1001 components and 5004 component-terminals.
 [INFO ODB-0132]     Created 2 special nets and 0 connections.
 [INFO ODB-0133]     Created 2 nets and 1001 connections.
-[INFO RSZ-0058] Using max wire length 2393um.
+[INFO RSZ-0058] Using max wire length 2406um.
 Iteration | Resized | Buffers | Nets repaired | Remaining
 ---------------------------------------------------------
         0 |       0 |       0 |             0 |      1002

src/rsz/test/repair_design4.ok

@@ -10,8 +10,8 @@ Pin                                   Limit Fanout  Slack
 ---------------------------------------------------------
 drvr/Q                                   10     35    -25 (VIOLATED)
 
-[INFO RSZ-0058] Using max wire length 527um.
-[INFO RSZ-0058] Using max wire length 527um.
+[INFO RSZ-0058] Using max wire length 530um.
+[INFO RSZ-0058] Using max wire length 530um.
 [INFO RSZ-0035] Found 1 fanout violations.
 [INFO RSZ-0038] Inserted 4 buffers in 1 nets.
 [INFO RSZ-0039] Resized 4 instances.

src/rsz/test/repair_design5.ok

@@ -4,7 +4,7 @@
 [INFO ODB-0131]     Created 36 components and 216 component-terminals.
 [INFO ODB-0132]     Created 2 special nets and 72 connections.
 [INFO ODB-0133]     Created 2 nets and 72 connections.
-[INFO RSZ-0058] Using max wire length 527um.
+[INFO RSZ-0058] Using max wire length 530um.
 [INFO RSZ-0035] Found 1 fanout violations.
 [INFO RSZ-0038] Inserted 4 buffers in 1 nets.
 [INFO RSZ-0039] Resized 3 instances.
@@ -18,7 +18,7 @@ Instance drvr
  Output pins:
   Q output net0
   QN output (unconnected)
-[INFO RSZ-0058] Using max wire length 527um.
+[INFO RSZ-0058] Using max wire length 530um.
 [INFO RSZ-0039] Resized 1 instances.
 Instance drvr
  Cell: DFF_X2

src/rsz/test/repair_fanout1.ok

@@ -10,7 +10,7 @@ Pin                                   Limit Fanout  Slack
 ---------------------------------------------------------
 drvr/Q                                   10     35    -25 (VIOLATED)
 
-[INFO RSZ-0058] Using max wire length 527um.
+[INFO RSZ-0058] Using max wire length 530um.
 [INFO RSZ-0035] Found 1 fanout violations.
 [INFO RSZ-0038] Inserted 4 buffers in 1 nets.
 [INFO RSZ-0039] Resized 4 instances.

src/rsz/test/repair_fanout5.ok

@@ -10,7 +10,7 @@ Pin                                   Limit Fanout  Slack
 ---------------------------------------------------------
 in1                                      10     35    -25 (VIOLATED)
 
-[INFO RSZ-0058] Using max wire length 527um.
+[INFO RSZ-0058] Using max wire length 530um.
 [INFO RSZ-0035] Found 1 fanout violations.
 [INFO RSZ-0038] Inserted 4 buffers in 1 nets.
 [INFO RSZ-0039] Resized 3 instances.

src/rsz/test/repair_fanout6.ok

@@ -7,7 +7,7 @@
 [INFO RSZ-0035] Found 1 fanout violations.
 [INFO RSZ-0038] Inserted 508 buffers in 1 nets.
 [INFO RSZ-0039] Resized 509 instances.
-worst slack -8.65
+worst slack -8.67
 max fanout
 
 Pin                                   Limit Fanout  Slack
@@ -17,6 +17,6 @@ fanout1/X                                20     20      0 (MET)
 [INFO RSZ-0094] Found 6400 endpoints with setup violations.
 [INFO RSZ-0099] Repairing 1 out of 6400 (0.00%) violating endpoints...
 [INFO RSZ-0045] Inserted 17 buffers, 1 to split loads.
-[INFO RSZ-0041] Resized 150 instances.
+[INFO RSZ-0041] Resized 162 instances.
 [WARNING RSZ-0062] Unable to repair all setup violations.
 worst slack -3.10

src/rsz/test/repair_setup2.ok

@@ -16,7 +16,7 @@ worst slack -0.28
 ---------------------------------------------------------------------------------------------------
         0 |       0 |       0 |        0 |      0 |     0 |   -0.117 |       -0.2 |      2 | y2
         5 |       0 |       0 |        0 |      0 |     2 |   -0.117 |       -0.2 |      2 | y2
-        7 |       0 |       0 |        0 |      0 |     3 |   -0.117 |       -0.2 |      2 | y2
+        8 |       0 |       0 |        0 |      0 |     3 |   -0.117 |       -0.2 |      2 | y2
     final |       0 |       0 |        0 |      0 |     3 |   -0.117 |       -0.2 |      2 | y2
 ---------------------------------------------------------------------------------------------------
 [INFO RSZ-0043] Swapped pins on 3 instances.

src/rsz/test/repair_setup4.ok

@@ -10,7 +10,7 @@ tns -6.294
 [INFO RSZ-0099] Repairing 6 out of 6 (100.00%) violating endpoints...
 [INFO RSZ-0059] Removed 4 buffers.
 [INFO RSZ-0040] Inserted 2 buffers.
-[INFO RSZ-0041] Resized 3 instances.
+[INFO RSZ-0041] Resized 2 instances.
 [WARNING RSZ-0062] Unable to repair all setup violations.
 Repair timing output passed/skipped equivalence test
 worst slack -0.44

src/rsz/test/repair_setup4_verbose.ok

@@ -11,25 +11,24 @@ worst slack -1.954
           | Buffers |  Gates  | Buffers  |  Gates | Swaps |          |            | Endpts | Endpt
 ---------------------------------------------------------------------------------------------------
         0 |       0 |       0 |        0 |      0 |     0 |   -1.954 |       -6.3 |      6 | r2/D
-        9 |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-       10 |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-       10 |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-       11 |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-       12 |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-       13 |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-       14 |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-      15* |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-      16* |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-      17* |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-      18* |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-      19* |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-      20* |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-      20* |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
-    final |       4 |       3 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+        8 |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+        9 |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+       10 |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+       10 |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+       11 |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+       12 |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+       13 |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+      14* |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+      15* |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+      16* |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+      17* |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+      18* |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+      19* |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
+    final |       4 |       2 |        3 |      0 |     0 |   -0.439 |       -2.2 |      6 | r7/D
 ---------------------------------------------------------------------------------------------------
 [INFO RSZ-0059] Removed 4 buffers.
 [INFO RSZ-0040] Inserted 2 buffers.
-[INFO RSZ-0041] Resized 3 instances.
+[INFO RSZ-0041] Resized 2 instances.
 [WARNING RSZ-0062] Unable to repair all setup violations.
 Repair timing output passed/skipped equivalence test
 worst slack -0.439

src/rsz/test/repair_setup7.ok

@@ -8,7 +8,7 @@ worst slack -1.95
 [INFO RSZ-0094] Found 6 endpoints with setup violations.
 [INFO RSZ-0099] Repairing 6 out of 6 (100.00%) violating endpoints...
 [INFO RSZ-0040] Inserted 3 buffers.
-[INFO RSZ-0041] Resized 44 instances.
+[INFO RSZ-0041] Resized 41 instances.
 [WARNING RSZ-0062] Unable to repair all setup violations.
 Repair timing output passed/skipped equivalence test
-worst slack -0.65
+worst slack -0.63

src/rsz/test/repair_setup_undo.ok

@@ -11,7 +11,7 @@ tns -6.294
 [INFO RSZ-0099] Repairing 6 out of 6 (100.00%) violating endpoints...
 [INFO RSZ-0059] Removed 4 buffers.
 [INFO RSZ-0040] Inserted 2 buffers.
-[INFO RSZ-0041] Resized 3 instances.
+[INFO RSZ-0041] Resized 2 instances.
 [WARNING RSZ-0062] Unable to repair all setup violations.
 post repair_timing QoR
 worst slack -0.44

src/rsz/test/repair_slew13.ok

@@ -12,7 +12,7 @@ Pin                                    Limit    Slew   Slack
 ------------------------------------------------------------
 b1/A                                    0.03    0.07   -0.04 (VIOLATED)
 
-[INFO RSZ-0058] Using max wire length 2393um.
+[INFO RSZ-0058] Using max wire length 2406um.
 [INFO RSZ-0034] Found 1 slew violations.
 [INFO RSZ-0039] Resized 1 instances.
 max slew

src/rsz/test/repair_slew14.ok

@@ -11,7 +11,7 @@ Pin                                    Limit    Slew   Slack
 ------------------------------------------------------------
 u2/A                                    1.50    1.81   -0.31 (VIOLATED)
 
-[INFO RSZ-0058] Using max wire length 2393um.
+[INFO RSZ-0058] Using max wire length 2406um.
 [INFO RSZ-0034] Found 1 slew violations.
 [INFO RSZ-0036] Found 1 capacitance violations.
 [INFO RSZ-0038] Inserted 2 buffers in 1 nets.

src/rsz/test/repair_slew6.ok

@@ -61,5 +61,5 @@ r7/D                                    1.50    3.33   -1.83 (VIOLATED)
 r8/D                                    1.50    3.33   -1.83 (VIOLATED)
 r9/D                                    1.50    3.33   -1.83 (VIOLATED)
 
-[INFO RSZ-0058] Using max wire length 2393um.
+[INFO RSZ-0058] Using max wire length 2406um.
 [INFO RSZ-0039] Resized 1 instances.

src/rsz/test/repair_slew7.ok

@@ -34,8 +34,8 @@ Pin                                    Limit     Cap   Slack
 ------------------------------------------------------------
 u1/ZN                                  10.47   15.05   -4.58 (VIOLATED)
 
-[INFO RSZ-0058] Using max wire length 1229um.
-[INFO RSZ-0039] Resized 3 instances.
+[INFO RSZ-0058] Using max wire length 1247um.
+[INFO RSZ-0039] Resized 1 instances.
 Startpoint: u1/A4 (internal pin)
 Endpoint: out1 (output port)
 Path Group: unconstrained
@@ -46,9 +46,9 @@ Corner: slow
 -----------------------------------------------------------------------
            0.00    0.00    0.00 v u1/A4 (NOR4_X4)
   14.64    0.24    0.40    0.40 ^ u1/ZN (NOR4_X4)
-   1.44    0.06    0.14    0.54 v u2/ZN (NAND4_X1)
-   0.77    0.02    0.11    0.65 v x2/Z (CLKBUF_X1)
-           0.02    0.00    0.65 v out1 (out)
+   1.61    0.06    0.14    0.54 v u2/ZN (NAND4_X1)
+   0.77    0.01    0.11    0.65 v x2/Z (BUF_X1)
+           0.01    0.00    0.65 v out1 (out)
                            0.65   data arrival time
 -----------------------------------------------------------------------
 (Path is unconstrained)