synthesis: better reports for exploring MAX_UNGROUP_SIZE

Seperate the concern of collecting area of modules and implementing
a policy.

First a report is collected, such as:

$ cat results/asap7/riscv32i/base/keep_hierarchy.tcl
0.291600 $paramod\mux2\WIDTH=s32'00000000000000000000000000000001
0.306180 \magcompare2c
0.641520 \magcompare2b
0.801900 $paramod\mux2\WIDTH=s32'00000000000000000000000000000100
0.991440 $paramod\mux2\WIDTH=s32'00000000000000000000000000000101
2.084940 \ROM
3.076380 \aludec
4.009500 \maindec
6.794280 $paramod\mux2\WIDTH=s32'00000000000000000000000000100000
6.794280 $paramod\mux2\WIDTH=s32'00000000000000000000000000100000

In synthesis, MAX_UNGROUP_SIZE is used to select which
of these modules to keep and which to flatten.

For some design there is little guesswork involved when looking
at this report and picking a MAX_UNGROUP_SIZE.

The names of targets in the makefile, variables and report
names could be revised to reflect this seperation of concerns
to improve readability, but leave that for a followup PR.

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/scripts/synth.tcl

@@ -1,9 +1,31 @@
 source $::env(SCRIPTS_DIR)/synth_preamble.tcl
 
-source $::env(SYNTH_STOP_MODULE_SCRIPT)
+hierarchy -check -top $::env(DESIGN_NAME)
+
+set ungroup_threshold 0
+if { $::env(MAX_UNGROUP_SIZE) > 0 } {
+  set ungroup_threshold $::env(MAX_UNGROUP_SIZE)
+  puts "Ungroup modules of size greater than $ungroup_threshold"
+}
+
+set fp [open $::env(SYNTH_STOP_MODULE_SCRIPT) r]
+while {[gets $fp line] != -1} {
+    set fields [split $line " "]
+    set area [lindex $fields 0]
+    set module_name [lindex $fields 1]
+
+    if {[expr $area > $ungroup_threshold]} {
+      puts "Keeping $area $module_name"
+      select -module $module_name
+      setattr -mod -set keep_hierarchy 1
+      select -clear
+    } else {
+      puts "Flattening $area $module_name"
+    }
+}
+close $fp
 
 if { [env_var_equals SYNTH_GUT 1] } {
-  hierarchy -check -top $::env(DESIGN_NAME)
   # /deletes all cells at the top level, which will quickly optimize away
   # everything else, including macros.
   delete $::env(DESIGN_NAME)/c:*

flow/scripts/synth_hier_report.tcl

@@ -25,11 +25,6 @@ proc write_keep_hierarchy {} {
 
   tee -o $::env(REPORTS_DIR)/synth_hier_stat.txt stat {*}$stat_libs
 
-  set ungroup_threshold 0
-  if { [env_var_exists_and_non_empty MAX_UNGROUP_SIZE] && $::env(MAX_UNGROUP_SIZE) > 0 } {
-    set ungroup_threshold $::env(MAX_UNGROUP_SIZE)
-    puts "Ungroup modules of size $ungroup_threshold"
-  }
   hierarchy -check -top $::env(DESIGN_NAME)
   set fptr [open $::env(REPORTS_DIR)/synth_hier_stat.txt r]
   set contents [read -nonewline $fptr]
@@ -53,8 +48,8 @@ proc write_keep_hierarchy {} {
       }
     }
   }
-  set out_script_ptr [open $::env(SYNTH_STOP_MODULE_SCRIPT) w]
-  puts $out_script_ptr "hierarchy -check -top $::env(DESIGN_NAME)"
+
+  set areas {}
   foreach module $module_list {
     tee -o $::env(REPORTS_DIR)/synth_hier_stat_temp_module.txt stat -top "$module" {*}$stat_libs
     set fptr1 [open $::env(REPORTS_DIR)/synth_hier_stat_temp_module.txt r]
@@ -63,18 +58,17 @@ proc write_keep_hierarchy {} {
     set split_cont1 [split $contents1 "\n"]
     foreach line $split_cont1 {
       if {[regexp { +Chip area for top module '(\S+)': (.*)} $line -> module_name area]} {
-        if {[expr $area > $ungroup_threshold]} {
-            puts "Preserving module: $module_name (area: $area)"
-            puts $out_script_ptr "select -module {$module_name}"
-            puts $out_script_ptr "setattr -mod -set keep_hierarchy 1"
-            puts $out_script_ptr "select -clear"
-        } else {
-          puts "Flattening module $module_name (area: $area)"
-        }
+        lappend areas "$area $module_name"
       }
     }
     file delete -force $::env(REPORTS_DIR)/synth_hier_stat_temp_module.txt
   }
+  set areas [lsort -index 0 -real $areas]
+
+  set out_script_ptr [open $::env(SYNTH_STOP_MODULE_SCRIPT) w]
+  foreach {line} $areas {
+    puts $out_script_ptr $line
+  }
   close $out_script_ptr
 }