Merge pull request The-OpenROAD-Project#3792 from openroadie/recover_…

…power

Recover power

src/rsz/README.md

@@ -168,21 +168,23 @@ repair_timing [-setup]
               [-setup_margin setup_margin]
               [-hold_margin hold_margin]
               [-allow_setup_violations]
+              [-recover_power percent_of_paths_with_slack]
               [-repair_tns tns_end_percent]
               [-max_utilization util]
               [-max_buffer_percent buffer_percent]
               [-verbose]
 ```
 
-The `repair_timing` command repairs setup and hold violations.  It
-should be run after clock tree synthesis with propagated clocks.
-Setup repair is done before hold repair so that hold repair does not
-cause setup checks to fail. While repairing hold violations buffers
-are not inserted that will cause setup violations unless
-`-allow_setup_violations` is specified.
+The `repair_timing` command repairs setup and hold violations.  It can also 
+recover power from paths with positive slack by downsizing or using higher
+Vt cells (if they are available). It should be run after clock tree synthesis 
+with propagated clocks. Setup repair is done before hold repair so that hold 
+repair does not cause setup checks to fail. While repairing hold violations buffers
+are not inserted that will cause setup violations unless `-allow_setup_violations` 
+is specified.
+
 Use `-setup_margin/-hold_margin` to add additional slack margin.
-Use `-verbose` to print more information about the progress of the
-repair.
+Use `-verbose` to print more information about the progress of the repair.
 
 The worst setup path is always repaired.  Next, violating paths to
 endpoints are repaired to reduced the total negative slack.  The
@@ -196,6 +198,10 @@ Use`-max_buffer_percent` to specify a maximum number of buffers to insert
 to repair hold violations as a percentage of the number of instances
 in the design. The default value for `buffer_percent` is 20, for 20%.
 
+Use`-recover_power` to specify the percent of paths with positive slack which
+will be considered for gate resizing to save power. It is recommended that
+this option be used with global routing based parasitics. 
+
 ### Repair Clock Nets
 
 ```

src/rsz/include/rsz/Resizer.hh

@@ -254,7 +254,7 @@ public:
   int holdBufferCount() const;
 
   ////////////////////////////////////////////////////////////////
-  void recoverPower();
+  void recoverPower(float recover_power_percent);
 
   ////////////////////////////////////////////////////////////////
   // Area of the design in meter^2.

src/rsz/src/RecoverPower.cc

@@ -107,7 +107,7 @@ RecoverPower::init()
 }
 
 void
-RecoverPower::recoverPower()
+RecoverPower::recoverPower(float recover_power_percent)
 {
   init();
   float setup_slack_margin = 1e-11;
@@ -140,7 +140,12 @@ RecoverPower::recoverPower()
              int(ends_with_slack.size() / double(endpoints->size()) * 100));
 
   int end_index = 0;
-  int max_end_count = ends_with_slack.size()/5; // 20%
+  int max_end_count = ends_with_slack.size()*recover_power_percent;
+
+  // As long as we are here fix at least one path
+  if (max_end_count == 0) {
+    max_end_count = 1;
+}
 
   resizer_->incrementalParasiticsBegin();
   for (Vertex *end : ends_with_slack) {
@@ -194,7 +199,6 @@ RecoverPower::recoverPower()
   }
 
   resizer_->incrementalParasiticsEnd();
-
   // TODO: Add the appropriate metric here
   // logger_->metric("design__instance__count__setup_buffer", inserted_buffer_count_);
   if (resize_count_ > 0) {
@@ -203,7 +207,6 @@ RecoverPower::recoverPower()
   if (resizer_->overMaxArea()) {
     logger_->error(RSZ, 125, "max utilization reached.");
   }
-
 }
 
 // For testing.

src/rsz/src/RecoverPower.hh

@@ -79,7 +79,7 @@ class RecoverPower : StaState
 {
 public:
   RecoverPower(Resizer *resizer);
-  void recoverPower();
+  void recoverPower(float recover_power_percent);
   // For testing.
   void recoverPower(const Pin *end_pin);
   // Rebuffer one net (for testing).

src/rsz/src/Resizer.cc

@@ -2640,13 +2640,13 @@ Resizer::holdBufferCount() const
 
 ////////////////////////////////////////////////////////////////
 void
-Resizer::recoverPower()
+Resizer::recoverPower(float recover_power_percent)
 {
   resizePreamble();
   if (parasitics_src_ == ParasiticsSrc::global_routing) {
     opendp_->initMacrosAndGrid();
   }
-  recover_power_->recoverPower();
+  recover_power_->recoverPower(recover_power_percent);
 }
 ////////////////////////////////////////////////////////////////
 // Journal to roll back changes (OpenDB not up to the task).

src/rsz/src/Resizer.i

@@ -537,11 +537,11 @@ hold_buffer_count()
 
 ////////////////////////////////////////////////////////////////
 void
-recover_power()
+recover_power(float recover_power_percent)
 {
   ensureLinked();
   Resizer *resizer = getResizer();
-  resizer->recoverPower();
+  resizer->recoverPower(recover_power_percent);
 }
 
 ////////////////////////////////////////////////////////////////

src/rsz/src/Resizer.tcl

@@ -389,7 +389,7 @@ proc repair_tie_fanout { args } {
 
 # -max_passes is for developer debugging so intentionally not documented
 # in define_cmd_args
-sta::define_cmd_args "repair_timing" {[-setup] [-hold] [-recover_power]\
+sta::define_cmd_args "repair_timing" {[-setup] [-hold] [-recover_power percent_of_paths_with_slack]\
                                         [-setup_margin setup_margin]\
                                         [-hold_margin hold_margin]\
                                         [-allow_setup_violations]\
@@ -404,12 +404,12 @@ proc repair_timing { args } {
   sta::parse_key_args "repair_timing" args \
     keys {-setup_margin -hold_margin -slack_margin \
             -libraries -max_utilization -max_buffer_percent \
-            -repair_tns -max_passes} \
-    flags {-setup -hold -recover_power -allow_setup_violations -skip_pin_swap -skip_gate_cloning -verbose}
+            -recover_power -repair_tns -max_passes} \
+    flags {-setup -hold -allow_setup_violations -skip_pin_swap -skip_gate_cloning -verbose}
 
   set setup [info exists flags(-setup)]
   set hold [info exists flags(-hold)]
-  set recover_power [info exists flags(-recover_power)]
+
   if { !$setup && !$hold } {
     set setup 1
     set hold 1
@@ -448,6 +448,13 @@ proc repair_timing { args } {
     set repair_tns_end_percent [expr $repair_tns_end_percent / 100.0]
   }
 
+  set recover_power_percent -1
+  if { [info exists keys(-recover_power)] } {
+    set recover_power_percent $keys(-recover_power)
+    sta::check_percent "-recover_power" $recover_power_percent
+    set recover_power_percent [expr $recover_power_percent / 100.0]
+  }
+
   set verbose 0
   if { [info exists flags(-verbose)] } {
     set verbose 1
@@ -459,8 +466,8 @@ proc repair_timing { args } {
   }
   sta::check_argc_eq0 "repair_timing" $args
   rsz::check_parasitics
-  if { $recover_power } {
-    rsz::recover_power	
+  if { $recover_power_percent >= 0 } {
+    rsz::recover_power $recover_power_percent
   } else {
       if { $setup } {
     rsz::repair_setup $setup_margin $repair_tns_end_percent $max_passes \