Fix `--stats` overridden by skipping identical build (#6220).

Changes

@@ -45,6 +45,7 @@ Verilator 5.039 devel
 * Fix VPI signal range order (#6189) (#6200). [Ibrahim Burak Yorulmaz]
 * Fix structure select causing 'Wide Op' error (#6191). [Danny Oler]
 * Fix 'driver same component' assertion (#6211) (#6215). [Geza Lore]
+* Fix `--stats` overridden by skipping identical build (#6220). [Geza Lore]
 
 
 Verilator 5.038 2025-07-08

src/Verilator.cpp

@@ -651,7 +651,8 @@ static void process() {
     if (v3Global.opt.stats()) V3Stats::statsStage("emit");
 }
 
-static void verilate(const string& argString) {
+static bool verilate(const string& argString) {
+    // Run verilation, and return false if skipped
     UINFO(1, "Option --verilate: Start Verilation");
 
     // Can we skip doing everything if times are ok?
@@ -661,7 +662,7 @@ static void verilate(const string& argString) {
                                   + "__verFiles.dat",
                               argString)) {
         UINFO(1, "--skip-identical: No change to any source files, exiting");
-        return;
+        return false;
     }
     // Undocumented debugging - cannot be a switch as then command line
     // would mismatch forcing non-identicalness when we set it
@@ -775,10 +776,12 @@ static void verilate(const string& argString) {
     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;
 }
 
 static string buildMakeCmd(const string& makefile, const string& target) {
@@ -862,8 +865,9 @@ int main(int argc, char** argv) {
 
     V3Error::abortIfErrors();
 
+    bool didVerilate = false;
     if (v3Global.opt.verilate()) {
-        verilate(argString);
+        didVerilate = verilate(argString);
     } else {
         UINFO(1, "Option --no-verilate: Skip Verilation");
     }
@@ -874,7 +878,7 @@ int main(int argc, char** argv) {
         execBuildJob();
     }
 
-    reportStatsIfEnabled();
+    if (didVerilate) reportStatsIfEnabled();
     V3DiagSarif::output(true);
 
     // Explicitly release resources

test_regress/t/t_flag_skipidentical.py

@@ -10,27 +10,35 @@
 import vltest_bootstrap
 import time
 
+FileTimes = {}
+
+
+def prep_output_file(filename):
+    oldstats = os.path.getmtime(filename)
+    if not oldstats:
+        test.error("No output file found: " + filename)
+    print("Old %s mtime=%d" % (filename, oldstats))
+    FileTimes[filename] = oldstats
+
+
 test.scenarios('vlt')
 
-test.compile()
+test.compile(verilator_flags2=['--stats'])
 
 print("NOTE: use --debugi, as --debug in driver turns off skip-identical")
 
-outfile = test.obj_dir + "/V" + test.name + ".cpp"
-oldstats = os.path.getmtime(outfile)
-if not oldstats:
-    test.error("No output file found: " + outfile)
-print("Old mtime=", oldstats)
+prep_output_file(test.obj_dir + "/V" + test.name + ".cpp")
+prep_output_file(test.obj_dir + "/V" + test.name + "__stats.txt")
 
 time.sleep(2)  # Or else it might take < 1 second to compile and see no diff.
 
 test.setenv('VERILATOR_DEBUG_SKIP_IDENTICAL', "1")
-test.compile()
+test.compile(verilator_flags2=['--stats'])
 
-newstats = os.path.getmtime(outfile)
-print("New mtime=", newstats)
-
-if oldstats != newstats:
-    test.error("--skip-identical was ignored -- recompiled")
+for filename, oldtime in FileTimes.items():
+    newstats = os.path.getmtime(filename)
+    print("New %s mtime=%d" % (filename, newstats))
+    if oldtime != newstats:
+        test.error("--skip-identical was ignored -- regenerated %s" % (filename))
 
 test.passes()