[NFC] Fix fuzzer counting of ignored runs due to many errors (WebAsse…

…mbly#6444)

When the interpreter sees that most exports simply trap we mark the
iteration as ignored. But we run the interpreter on the before wasm
and also the after wasm, so we were incrementing that counter by 2
each time, which could be misleading.

scripts/fuzz_opt.py

@@ -632,12 +632,12 @@ def fix_spec_output(out):
 
 # Notes a VM run that we ignore, and the reason for it (for metrics purposes).
 # Extra text can also be printed that is not included in the metrics.
-def note_ignored_vm_run(reason, extra_text=''):
+def note_ignored_vm_run(reason, extra_text='', amount=1):
     global ignored_vm_runs
     print(f'(ignore VM run: {reason}{extra_text})')
-    ignored_vm_runs += 1
+    ignored_vm_runs += amount
     ignored_vm_run_reasons.setdefault(reason, 0)
-    ignored_vm_run_reasons[reason] += 1
+    ignored_vm_run_reasons[reason] += amount
 
 
 def run_vm(cmd):
@@ -784,7 +784,15 @@ def run(self, wasm):
                         # still be useful testing here (up to 50%), so we only
                         # note that this is a mostly-ignored run, but we do not
                         # ignore the parts that are useful.
-                        note_ignored_vm_run('too many errors vs calls', extra_text=f' ({calls} calls, {errors} errors)')
+                        #
+                        # Note that we set amount to 0.5 because we are run both
+                        # on the before wasm and the after wasm. Those will be
+                        # in sync (because the optimizer does not remove traps)
+                        # and so by setting 0.5 we only increment by 1 for the
+                        # entire iteration.
+                        note_ignored_vm_run('too many errors vs calls',
+                                            extra_text=f' ({calls} calls, {errors} errors)',
+                                            amount=0.5)
                 return output
 
             def can_run(self, wasm):