diff --git a/tests/test_other.py b/tests/test_other.py
index 9b4313b8fd090..a13de53a475f8 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -1951,16 +1951,19 @@ def fix(src):
               return map(fix, src)
             src = '\n'.join(filter(lambda line: 'var ' not in line, src.split('\n'))) # ignore vars
             def reorder(func):
-              # emit EYE_ONE always before EYE_TWO, replaceing i1,i2 or i2,i1
-              i1 = 'i1'
-              i2 = 'i2'
-              if i1 not in func or i2 not in func: return func
-              ok = func.index(i1) < func.index(i2)
-              if not ok:
-                i1 = 'i2'
-                i2 = 'i1'
-              func = func.replace(i1, 'EYE_ONE').replace(i2, 'EYE_TWO')
-              assert func.index('EYE_ONE') < func.index('EYE_TWO')
+              def swap(func, i1, i2):
+                # emit EYE_ONE always before EYE_TWO, replacing i1,i2 or i2,i1 etc
+                if i1 not in func or i2 not in func: return func
+                ok = func.index(i1) < func.index(i2)
+                if not ok:
+                  temp = i1
+                  i1 = i2
+                  i2 = temp
+                func = func.replace(i1, 'EYE_ONE').replace(i2, 'EYE_TWO')
+                assert func.index('EYE_ONE') < func.index('EYE_TWO')
+                return func
+              func = swap(func, 'i1', 'i2')
+              func = swap(func, 'i4', 'i5')
               return func
             src = 'function '.join(map(reorder, src.split('function ')))
             return src
diff --git a/tools/optimizer/optimizer.cpp b/tools/optimizer/optimizer.cpp
index 4e3475e37a234..3f83408c5f921 100644
--- a/tools/optimizer/optimizer.cpp
+++ b/tools/optimizer/optimizer.cpp
@@ -516,7 +516,8 @@ Ref makeAsmCoercion(Ref node, AsmType type) {
 // Checks
 
 bool isEmpty(Ref node) {
-  return node->size() == 2 && node[0] == TOPLEVEL && node[1]->size() == 0;
+  return (node->size() == 2 && node[0] == TOPLEVEL && node[1]->size() == 0) ||
+          (node->size() > 0 && node[0] == BLOCK && (!node[1] || node[1]->size() == 0));
 }
 
 bool commable(Ref node) { // TODO: hashing
@@ -664,7 +665,6 @@ void clearUselessNodes(Ref arr) {
 
 void removeAllEmptySubNodes(Ref ast) {
   traversePre(ast, [](Ref node) {
-    int index = -1;
     if (node[0] == DEFUN) {
       clearEmptyNodes(node[3]);
     } else if (node[0] == BLOCK && node->size() > 1 && !!node[1]) {
@@ -675,15 +675,31 @@ void removeAllEmptySubNodes(Ref ast) {
   });
 }
 void removeAllUselessSubNodes(Ref ast) {
-  traversePre(ast, [](Ref node) {
-    int index = -1;
-    if (node[0] == DEFUN) {
+  traversePrePost(ast, [](Ref node) {
+    Ref type = node[0];
+    if (type == DEFUN) {
       clearUselessNodes(node[3]);
-    } else if (node[0] == BLOCK && node->size() > 1 && !!node[1]) {
+    } else if (type == BLOCK && node->size() > 1 && !!node[1]) {
       clearUselessNodes(node[1]);
-    } else if (node[0] == SEQ && isEmpty(node[1])) {
+    } else if (type == SEQ && isEmpty(node[1])) {
       safeCopy(node, node[2]);
     }
+  }, [](Ref node) {
+    Ref type = node[0];
+    if (type == IF) {
+      bool empty2 = isEmpty(node[2]), has3 = node->size() == 4 && !!node[3], empty3 = !has3 || isEmpty(node[3]);
+      if (!empty2 && empty3 && has3) { // empty else clauses
+        node->setSize(3);
+      } else if (empty2 && !empty3) { // empty if blocks
+        safeCopy(node, make2(IF, make2(UNARY_PREFIX, L_NOT, node[1]), node[3]));
+      } else if (empty2 && empty3) {
+        if (hasSideEffects(node[1])) {
+          safeCopy(node, make1(STAT, node[1]));
+        } else {
+          safeCopy(node, makeEmpty());
+        }
+      }
+    }
   });
 }
 
diff --git a/tools/test-js-optimizer-asm-regs-output.js b/tools/test-js-optimizer-asm-regs-output.js
index c75bbcf74dab3..ca2f6069f8bd7 100644
--- a/tools/test-js-optimizer-asm-regs-output.js
+++ b/tools/test-js-optimizer-asm-regs-output.js
@@ -106,5 +106,20 @@ function iffey() {
 function nops() {
  var i1 = 0;
  f(i1);
+ if (cheez) {
+  doIt();
+ } else {
+  doIt();
+ }
+ if (cheez) {
+  doIt();
+ }
+ if (!cheez) {
+  doIt();
+ }
+ if (!cheez) {
+  doIt();
+ }
+ doIt();
 }
 
diff --git a/tools/test-js-optimizer-asm-regs.js b/tools/test-js-optimizer-asm-regs.js
index 9c5b49fd13056..a4d1fb96b2a0f 100644
--- a/tools/test-js-optimizer-asm-regs.js
+++ b/tools/test-js-optimizer-asm-regs.js
@@ -111,6 +111,23 @@ function nops() {
   x | 0;
   ~x;
   f(x);
+  // vaccuming
+  if (cheez) {
+   doIt();
+  } else {
+   doIt();
+  }
+  if (cheez) {
+   doIt();
+  } else {}
+  if (cheez) {} else {
+   doIt();
+  }
+  if (cheez) {} else {
+   doIt();
+  }
+  if (cheez) {} else {}
+  if (doIt()) {} else {}
 }
 // EMSCRIPTEN_GENERATED_FUNCTIONS: ["asm", "_doit", "stackRestore", "switchey", "switchey2", "iffey", "nops"]