Fix index register assignment in LoadFieldByIndex for arm, arm64, and mips.

test/mjsunit/regress/regress-368243.js

Index: test/mjsunit/regress/regress-368243.js
diff --git a/test/mjsunit/regress/regress-361608.js b/test/mjsunit/regress/regress-368243.js
similarity index 50%
copy from test/mjsunit/regress/regress-361608.js
copy to test/mjsunit/regress/regress-368243.js
index b3cc90cfd4b06afb3c7424758e23f91d685e3aa2..6647d1228685ddd7596438305fa63dfe6a28e7a0 100644
--- a/test/mjsunit/regress/regress-361608.js
+++ b/test/mjsunit/regress/regress-368243.js
@@ -4,17 +4,22 @@
 
 // Flags: --allow-natives-syntax
 
-function f() {};
-int_array = [1];
-
-function foo() {
-  var x;
-  for (var i = -1; i < 0; i++) {
-    x = int_array[i + 1];
-    f(function() { x = i; });
+function foo(a, c){
+  for(var f in c) {
+    if ("object" === typeof c[f]) {
+      a[f] = c[f];
+      foo(a[f], c[f]);
+    }
   }
-}
+};
+
+c = {
+  "one" : { x : 1},
+  "two" : { x : 2},
+  "thr" : { x : 3, z : 4},
+};
 
-foo();
+foo({}, c);
+foo({}, c);
 %OptimizeFunctionOnNextCall(foo);
-foo();
+foo({}, c);