do not try to eliminate phi variables, which are unsafe to be removed and the llvm optimizer will remove anyhow if unused

tools/eliminator/eliminator-test-output.js

@@ -6132,4 +6132,12 @@ function _mallocNoU($bytes) {
   return $mem_0;
   return null;
 }
+function phi() {
+  if (wat()) {
+    var $10 = 1;
+  } else {
+    var $10 = (_init_mparams() | 0) != 0;
+  }
+  var $10;
+}
 

tools/eliminator/eliminator-test.js

@@ -8828,5 +8828,15 @@ function _mallocNoU($bytes) {
   return $mem_0;
   return null;
 }
-// EMSCRIPTEN_GENERATED_FUNCTIONS: ["a", "b", "c", "f", "g", "h", "py", "r", "t", "f2", "f3", "llvm3_1", "_inflate", "_malloc", "_mallocNoU"]
+function phi() {
+  if (wat()) {
+    var $10 = 1;
+  } else {
+    var $7=_init_mparams();
+    var $8=(($7)|0)!=0;
+    var $10 = $8;
+  }
+  var $10;
+}
+// EMSCRIPTEN_GENERATED_FUNCTIONS: ["a", "b", "c", "f", "g", "h", "py", "r", "t", "f2", "f3", "llvm3_1", "_inflate", "_malloc", "_mallocNoU", "asm", "phi"]
 

tools/js-optimizer.js

@@ -1464,7 +1464,7 @@ function eliminate(ast, memSafe) {
     for (var name in locals) {
       if (definitions[name] == 1 && uses[name] == 1) {
         potentials[name] = 1;
-      } else if (uses[name] == 0) {
+      } else if (uses[name] == 0 && (!definitions[name] || definitions[name] <= 1)) { // no uses, no def or 1 def (cannot operate on phis, and the llvm optimizer will remove unneeded phis anyhow)
         var hasSideEffects = false;
         if (values[name]) {
           traverse(values[name], function(node, type) {