Fuzzer: Standardize notation for exception prefixes

scripts/fuzz_opt.py

@@ -477,6 +477,9 @@ def pick_initial_contents():
 # and also see the --dce workaround below that also links to those issues.
 V8_UNINITIALIZED_NONDEF_LOCAL = 'uninitialized non-defaultable local'
 
+# JS exceptions are logged as exception thrown: REASON
+EXCEPTION_PREFIX = 'exception thrown: '
+
 
 # given a call line that includes FUZZ_EXEC_CALL_PREFIX, return the export that
 # is called
@@ -584,7 +587,7 @@ def fix_double(x):
  out = re.sub(r'f64\.const (-?[nanN:abcdefxIity\d+-.]+)', fix_double, out)
 
  # mark traps from wasm-opt as exceptions, even though they didn't run in a vm
- out = out.replace(TRAP_PREFIX, 'exception: ' + TRAP_PREFIX)
+ out = out.replace(TRAP_PREFIX, EXCEPTION_PREFIX + TRAP_PREFIX)
 
  # funcref(0) has the index of the function in it, and optimizations can
  # change that index, so ignore it
@@ -594,6 +597,9 @@ def fix_double(x):
  # to "N".
  out = re.sub(r'i31ref\((-?\d+)\)', r'\1', out)
 
+ # Tag names may change due to opts, so canonicalize them.
+ out = re.sub(r' tag\$\d+', ' tag', out)
+
  lines = out.splitlines()
  for i in range(len(lines)):
  line = lines[i]
@@ -603,7 +609,7 @@ def fix_double(x):
  # developer can see it.
  print(line)
  lines[i] = None
- elif 'exception' in line:
+ elif EXCEPTION_PREFIX in line:
  # exceptions may differ when optimizing, but an exception should
  # occur, so ignore their types (also js engines print them out
  # slightly differently)

scripts/fuzz_shell.js

@@ -108,7 +108,7 @@ var instance;
 try {
  instance = new WebAssembly.Instance(module, imports);
 } catch (e) {
- console.log('exception: failed to instantiate module');
+ console.log('exception thrown: failed to instantiate module');
  quit();
 }
 
@@ -143,7 +143,7 @@ for (var e in exports) {
  console.log('[fuzz-exec] note result: ' + e + ' => ' + printed(result));
  }
  } catch (e) {
- console.log('exception!');// + [e, e.stack]);
+ console.log('exception thrown: ' + e);
  }
 }