make sure to set label if label is used in the emterpreter, as we will run aggressiveVariableElimination after it is no longer identifiable

emcc

@@ -1495,12 +1495,16 @@ try:
       js_optimizer_queue += [get_eliminate()]
 
       if shared.Settings.AGGRESSIVE_VARIABLE_ELIMINATION:
+        # note that this happens before registerize/minification, which can obfuscate the name of 'label', which is tricky
         js_optimizer_queue += ['aggressiveVariableElimination']
 
       js_optimizer_queue += ['simplifyExpressions']
 
-      if shared.Settings.EMTERPRETIFY: # emterpreter code will not run through a JS optimizing JIT, do more work ourselves
+      if shared.Settings.EMTERPRETIFY:
+        # emterpreter code will not run through a JS optimizing JIT, do more work ourselves
         js_optimizer_queue += ['localCSE']
+        # add explicit label setting, as we will run aggressiveVariableElimination late, *after* 'label' is no longer notable by name
+        js_optimizer_queue += ['safeLabelSetting']
 
       if shared.Settings.RELOOP and not shared.Settings.ASM_JS:
         js_optimizer_queue += ['optimizeShiftsAggressive', get_eliminate()] # aggressive shifts optimization requires loops, it breaks on switches

tests/fuzz/24.cpp.txt

@@ -0,0 +1 @@
+checksum = 1A282BA8

tools/js-optimizer.js

@@ -1075,6 +1075,30 @@ function localCSE(ast) {
   });
 }
 
+function safeLabelSetting(ast) {
+  // Add an assign to label, if it exists, so that even after we minify/registerize variable names, we can tell if any vars use the asm init value of 0 - none will, so it's easy to tell
+  assert(asm);
+  traverseGeneratedFunctions(ast, function(func) {
+    var asmData = normalizeAsm(func);
+    if ('label' in asmData.vars) {
+      var stats = getStatements(func);
+      var seenVar = false;
+      for (var i = 0; i < stats.length; i++) {
+        var curr = stats[i];
+        if (curr[0] === 'stat') curr = curr[1];
+        if (curr[0] === 'var') {
+          seenVar = true;
+        } else if (seenVar && curr[0] !== 'var') {
+          // first location after the vars
+          stats.splice(i+1, 0, ['stat', ['assign', true, ['name', 'label'], ['num', 0]]]);
+          break;
+        }
+      }
+    }
+    denormalizeAsm(func, asmData);
+  });
+}
+
 function simplifyIfs(ast) {
   traverseGeneratedFunctions(ast, function(func) {
     var simplifiedAnElse = false;
@@ -6326,7 +6350,7 @@ function emterpretify(ast) {
         }
         case 'var':
         case 'toplevel': {
-          assert(dropIt);
+          assert(dropIt || isEmptyNode(node));
           return [-1, []]; // empty node
         }
         case 'stat': return getReg(node[1], dropIt);
@@ -7229,7 +7253,7 @@ function emterpretify(ast) {
       stats.forEach(function(stat) {
         var before = freeLocals.length;
         var raw = getReg(stat, true);
-        //printErr('raw: ' + JSON.stringify(raw));
+        //printErr('raw: ' + JSON.stringify(stat));
         releaseIfFree(raw[0]);
         if (freeLocals.length !== before) assert(0, [before, freeLocals.length] + ' due to ' + astToSrc(stat)); // the statement is done - nothing should still be held on to
         var curr = raw[1];
@@ -7895,6 +7919,7 @@ var passes = {
   optimizeShiftsConservative: optimizeShiftsConservative,
   optimizeShiftsAggressive: optimizeShiftsAggressive,
   localCSE: localCSE,
+  safeLabelSetting: safeLabelSetting,
   simplifyIfs: simplifyIfs,
   hoistMultiples: hoistMultiples,
   loopOptimizer: loopOptimizer,