Enable cross-VM fuzzing + related improvements to fuzz_opt.py (#2762)

The main benefit here is comparing VMs, instead of just comparing
each VM to itself after opts. Comparing VMs is a little tricky since there
is room for nondeterminism with how results are printed and other
annoying things, which is why that didn't work well earlier.

With this PR I can run 10's of thousands of iterations without finding
any issues between v8 and the binaryen interpreter. That's after
fixing the various issues over the last few days as found by this:
#2760 #2757 #2750 #2752

Aside from that main benefit I ended up adding more improvements
to make it practical to do all that testing:

Randomize global fuzz settings like whether we allow NaNs and
out-of-bounds memory accesses. (This was necessary here since
we have to disable cross-VM comparisons if NaNs are enabled.)

Better logging of statistics like how many times each handler
was run.

Remove redundant FuzzExecImmediately handler (looks like
after past refactorings it was no longer adding any value).

Deterministic testcase handling: if you run e.g. fuzz_opt.py 42 it
will run one testcase and exactly the same one. If you run without
an argument it will run forever until it fails, and if it fails, it prints out
that ID so that you can easily reproduce it (I guess, on the same
binaryen + same python, not sure how python's deterministic
RNG changes between versions and builds).

Upgrade to Python 3.

1 files changed, 9 insertions, 9 deletions

diff --git a/test/passes/emit-js-wrapper=a.js.wast.js b/test/passes/emit-js-wrapper=a.js.wast.js
index 2e127d189..60f2449b0 100644
--- a/test/passes/emit-js-wrapper=a.js.wast.js
+++ b/test/passes/emit-js-wrapper=a.js.wast.js
@@ -21,13 +21,13 @@ if (typeof process === 'object' && typeof require === 'function' /* node.js dete
   }
 }
 function literal(x, type) {
-  var ret = type + '.const ';
+  var ret = '';
   switch (type) {
     case 'i32': ret += (x | 0); break;
     case 'f32':
     case 'f64': {
       if (x == 0 && (1 / x) < 0) ret += '-';
-      ret += x;
+      ret += Number(x).toString();
       break;
     }
     default: throw 'what?';
@@ -48,36 +48,36 @@ var instance = new WebAssembly.Instance(new WebAssembly.Module(binary), {
 });
 if (instance.exports.hangLimitInitializer) instance.exports.hangLimitInitializer();
 try {
-  console.log('[fuzz-exec] calling $add');
-  console.log('[fuzz-exec] note result: $add => ' + literal(instance.exports.add(0, 0), 'i32'));
+  console.log('[fuzz-exec] calling add');
+  console.log('[fuzz-exec] note result: add => ' + literal(instance.exports.add(0, 0), 'i32'));
 } catch (e) {
   console.log('exception!' /* + e */);
 }
 if (instance.exports.hangLimitInitializer) instance.exports.hangLimitInitializer();
 try {
-  console.log('[fuzz-exec] calling $no_return');
+  console.log('[fuzz-exec] calling no_return');
   instance.exports.no_return(0);
 } catch (e) {
   console.log('exception!' /* + e */);
 }
 if (instance.exports.hangLimitInitializer) instance.exports.hangLimitInitializer();
 try {
-  console.log('[fuzz-exec] calling $types');
+  console.log('[fuzz-exec] calling types');
   instance.exports.types(0, 0, 0, 0, 0);
 } catch (e) {
   console.log('exception!' /* + e */);
 }
 if (instance.exports.hangLimitInitializer) instance.exports.hangLimitInitializer();
 try {
-  console.log('[fuzz-exec] calling $types2');
+  console.log('[fuzz-exec] calling types2');
   instance.exports.types2(0, 0, 0);
 } catch (e) {
   console.log('exception!' /* + e */);
 }
 if (instance.exports.hangLimitInitializer) instance.exports.hangLimitInitializer();
 try {
-  console.log('[fuzz-exec] calling $types3');
-  console.log('[fuzz-exec] note result: $types3 => ' + literal(instance.exports.types3(0, 0, 0), 'i32'));
+  console.log('[fuzz-exec] calling types3');
+  console.log('[fuzz-exec] note result: types3 => ' + literal(instance.exports.types3(0, 0, 0), 'i32'));
 } catch (e) {
   console.log('exception!' /* + e */);
 }