remove side-effect-free nodes in registerize; enable registerize in native optimizer

tools/js_optimizer.py

@@ -9,7 +9,7 @@ __rootpath__ = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
 def path_from_root(*pathelems):
   return os.path.join(__rootpath__, *pathelems)
 
-NATIVE_PASSES = set(['asm', 'asmPreciseF32', 'receiveJSON', 'emitJSON', 'eliminate', 'eliminateMemSafe', 'simplifyExpressions', 'simplifyIfs', 'optimizeFrounds'])
+NATIVE_PASSES = set(['asm', 'asmPreciseF32', 'receiveJSON', 'emitJSON', 'eliminate', 'eliminateMemSafe', 'simplifyExpressions', 'simplifyIfs', 'optimizeFrounds', 'registerize'])
 
 JS_OPTIMIZER = path_from_root('tools', 'js-optimizer.js')
 

tools/optimizer/optimizer.cpp

@@ -829,6 +829,19 @@ void clearEmptyNodes(Ref arr) {
   }
   if (skip) arr->setSize(arr->size() - skip);
 }
+void clearUselessNodes(Ref arr) {
+  int skip = 0;
+  for (int i = 0; i < arr->size(); i++) {
+    Ref curr = arr[i];
+    if (skip) {
+      arr[i-skip] = curr;
+    }
+    if (isEmpty(deStat(curr)) || (curr[0] == STAT && !hasSideEffects(curr[1]))) {
+      skip++;
+    }
+  }
+  if (skip) arr->setSize(arr->size() - skip);
+}
 
 void removeAllEmptySubNodes(Ref ast) {
   traversePre(ast, [](Ref node) {
@@ -842,6 +855,18 @@ void removeAllEmptySubNodes(Ref ast) {
     }
   });
 }
+void removeAllUselessSubNodes(Ref ast) {
+  traversePre(ast, [](Ref node) {
+    int index = -1;
+    if (node[0] == DEFUN) {
+      clearUselessNodes(node[3]);
+    } else if (node[0] == BLOCK && !!node[1]) {
+      clearUselessNodes(node[1]);
+    } else if (node[0] == SEQ && isEmpty(node[1])) {
+      safeCopy(node, node[2]);
+    }
+  });
+}
 
 Ref unVarify(Ref vars) { // transform var x=1, y=2 etc. into (x=1, y=2), i.e., the same assigns, but without a var definition
   Ref ret = makeArray();
@@ -2348,7 +2373,7 @@ void registerize(Ref ast) {
         allVars.insert(node[1]->getIString());
       }
     });
-    removeAllEmptySubNodes(fun); // vacuum?
+    removeAllUselessSubNodes(fun); // vacuum?
     StringTypeMap regTypes; // reg name -> type
     auto getNewRegName = [&](int num, IString name) {
       const char *str;