Optimize away netlist teardown when about to exit (#8294)

src/Verilator.cpp

@@ -127,7 +127,6 @@ V3Global v3Global;
 static void reportStatsIfEnabled() {
     if (v3Global.opt.stats()) {
         FileLine::stats();
-        V3Stats::statsFinalAll(v3Global.rootp());
         V3Stats::statsReport();
     }
 }
@@ -207,10 +206,7 @@ static void process() {
             V3Hierarchical::createGraph(v3Global.rootp());
             // If a plan is created, further analysis is not necessary.
             // The actual Verilation will be done based on this plan.
-            if (v3Global.hierGraphp()) {
-                reportStatsIfEnabled();
-                return;
-            }
+            if (v3Global.hierGraphp()) return;
         }
 
         // Calculate and check widths, edit tree to TRUNC/EXTRACT any width mismatches
@@ -817,12 +813,6 @@ static bool verilate(const string& argString) {
     // Final writing shouldn't throw warnings, but...
     V3Error::abortIfWarnings();
 
-    // Free memory so compiler has more for --build
-    // No need to do this if skipped (above) as didn't alloc much
-    UINFO(1, "Releasing netlist memory");
-    v3Global.rootp()->deleteContents();
-    V3Os::releaseMemory();
-    if (v3Global.opt.stats()) V3Stats::statsStage("released");
     return true;
 }
 
@@ -846,10 +836,18 @@ static string buildMakeCmd(const string& makefile, const string& target) {
     return cmd.str();
 }
 
+static void releaseNetlistMemory() {
+    UINFO(1, "Releasing netlist memory");
+    v3Global.rootp()->deleteContents();
+    V3Os::releaseMemory();
+    if (v3Global.opt.stats()) V3Stats::statsStage("released");
+}
+
 static void execBuildJob() {
     UASSERT(v3Global.opt.build(), "--build is not specified.");
     UASSERT(v3Global.opt.gmake(), "--build requires GNU Make.");
     UASSERT(!v3Global.opt.makeJson(), "--build cannot use json build.");
+    releaseNetlistMemory();
     const VlOs::DeltaWallTime buildWallTime{true};
     UINFO(1, "Start Build");
 
@@ -866,6 +864,7 @@ static void execBuildJob() {
 
 static void execHierVerilation() {
     UASSERT(v3Global.hierGraphp(), "must be called only when plan exists");
+    releaseNetlistMemory();
     const string makefile = v3Global.opt.prefix() + "_hier.mk ";
     const string target = v3Global.opt.build() ? " hier_build" : " hier_verilation";
     const string cmdStr = buildMakeCmd(makefile, target);