[JS IR] Implement MoveTemporaryVariableDeclarationToAssignment optimization

js/js.translator/testData/js-optimizer/temporary-assignment/ifWithoutElse.optimized.js

@@ -3,18 +3,18 @@ function f(x) {
 }
 
 function box() {
-    var result1, result2, $a, $b;
+    var $a, $b;
 
     if (f(true)) {
         $a = "1";
     }
-    result1 = $a;
+    var result1 = $a;
     if (result1 !== "1") return "fail1: " + result1;
 
     if (f(false)) {
         $b = "1";
     }
-    result2 = $b;
+    var result2 = $b;
     if (result2 !== void 0) return "fail2: " + result2;
 
     return "OK";

js/js.translator/testData/js-optimizer/temporary-assignment/transitiveChain.optimized.js

@@ -13,32 +13,28 @@ function testIrregular() {
 }
 
 function testDoubleUse1() {
-    var $b;
-    $b = f("testDoubleUse1");
+    var $b = f("testDoubleUse1");
     var result = $b;
     f($b);
     return result;
 }
 
 function testDoubleUse2() {
-    var $d;
-    $d = f("testDoubleUse2");
+    var $d = f("testDoubleUse2");
     var result = $d;
     f($d);
     return result;
 }
 
 function testDoubleUse3() {
-    var $a;
-    $a = f("testDoubleUse3");
+    var $a = f("testDoubleUse3");
     var result = $a;
     f($a);
     return result;
 }
 
 function testCircular() {
-    var $b;
-    $b = f("testCircular");
+    var $b = f("testCircular");
     $b = $b;
     var result = $b;
     return result;