Eliminate unnecessary and unawesome instances of dynamic_cast<HphpArray*>

There are two dynamic_cast<HphpArray*> instances in bytecode.cpp that cause code to fail when using other types of arrays. However, the necessity of those casts seems to have disappeared in the meantime because simply removing them compiles and runs. I have ran full 'fbmake runtests' after removing the first cast (all passed). Then I removed the second cast (in lexical order) and ran the tests again. This time test/zend/good/ext-hash/hash_file_basic.php failed, but when I ran it again in separation it passed.

hphp/runtime/vm/bytecode.cpp

@@ -2096,7 +2096,7 @@ void VMExecutionContext::invokeFunc(TypedValue* retval,
   }
 #endif
 
-  HphpArray *arr = dynamic_cast<HphpArray*>(params.get());
+  ArrayData *arr = params.get();
   ExtraArgs* extraArgs = nullptr;
   if (isMagicCall) {
     // Put the method name into the location of the first parameter. We
@@ -2104,68 +2104,57 @@ void VMExecutionContext::invokeFunc(TypedValue* retval,
     m_stack.pushStringNoRc(invName);
     // Put array of arguments into the location of the second parameter
     m_stack.pushArray(arr);
-  } else {
-    Array hphpArrCopy(HphpArray::GetStaticEmptyArray());
-    if (UNLIKELY(!arr) && !params.empty()) {
-      // empty() check needed because we sometimes represent empty arrays
-      // as smart pointers with m_px == NULL, which freaks out
-      // ArrayData::merge.
-      hphpArrCopy.merge(params);
-      arr = dynamic_cast<HphpArray*>(hphpArrCopy.get());
-      assert(arr && arr->isHphpArray());
+  } else if (arr) {
+    const int numParams = f->numParams();
+    const int numExtraArgs = arr->size() - numParams;
+    if (numExtraArgs > 0 && (f->attrs() & AttrMayUseVV)) {
+      extraArgs = ExtraArgs::allocateUninit(numExtraArgs);
     }
-    if (arr) {
-      const int numParams = f->numParams();
-      const int numExtraArgs = arr->size() - numParams;
-      if (numExtraArgs > 0 && (f->attrs() & AttrMayUseVV)) {
-        extraArgs = ExtraArgs::allocateUninit(numExtraArgs);
-      }
-      int paramId = 0;
-      for (ssize_t i = arr->iter_begin();
-           i != ArrayData::invalid_index;
-           i = arr->iter_advance(i), ++paramId) {
-        TypedValue *from = arr->nvGetValueRef(i);
-        TypedValue *to;
-        if (LIKELY(paramId < numParams)) {
-          to = m_stack.allocTV();
-        } else {
-          if (!(f->attrs() & AttrMayUseVV)) {
-            // Discard extra arguments, since the function cannot
-            // possibly use them.
-            assert(extraArgs == nullptr);
-            ar->setNumArgs(numParams);
-            break;
-          }
-          assert(extraArgs != nullptr && numExtraArgs > 0);
-          // VarEnv expects the extra args to be in "reverse" order
-          // (i.e. the last extra arg has the lowest address)
-          to = extraArgs->getExtraArg(paramId - numParams);
+    int paramId = 0;
+    for (ssize_t i = arr->iter_begin();
+         i != ArrayData::invalid_index;
+         i = arr->iter_advance(i), ++paramId) {
+      TypedValue *from = arr->nvGetValueRef(i);
+      TypedValue *to;
+      if (LIKELY(paramId < numParams)) {
+        to = m_stack.allocTV();
+      } else {
+        if (!(f->attrs() & AttrMayUseVV)) {
+          // Discard extra arguments, since the function cannot
+          // possibly use them.
+          assert(extraArgs == nullptr);
+          ar->setNumArgs(numParams);
+          break;
         }
-        tvDup(from, to);
-        if (LIKELY(!f->byRef(paramId))) {
-          if (to->m_type == KindOfRef) {
-            tvUnbox(to);
+        assert(extraArgs != nullptr && numExtraArgs > 0);
+        // VarEnv expects the extra args to be in "reverse" order
+        // (i.e. the last extra arg has the lowest address)
+        to = extraArgs->getExtraArg(paramId - numParams);
+      }
+      tvDup(from, to);
+      if (LIKELY(!f->byRef(paramId))) {
+        if (to->m_type == KindOfRef) {
+          tvUnbox(to);
+        }
+      } else if (!(flags & InvokeIgnoreByRefErrors) &&
+                 (from->m_type != KindOfRef ||
+                  from->m_data.pref->_count == 2)) {
+        raise_warning("Parameter %d to %s() expected to be "
+                      "a reference, value given",
+                      paramId + 1, f->fullName()->data());
+        if (skipCufOnInvalidParams) {
+          if (extraArgs) {
+            int n = paramId >= numParams ? paramId - numParams + 1 : 0;
+            ExtraArgs::deallocate(extraArgs, n);
+            paramId -= n;
           }
-        } else if (!(flags & InvokeIgnoreByRefErrors) &&
-                   (from->m_type != KindOfRef ||
-                    from->m_data.pref->_count == 2)) {
-          raise_warning("Parameter %d to %s() expected to be "
-                        "a reference, value given",
-                        paramId + 1, f->fullName()->data());
-          if (skipCufOnInvalidParams) {
-            if (extraArgs) {
-              int n = paramId >= numParams ? paramId - numParams + 1 : 0;
-              ExtraArgs::deallocate(extraArgs, n);
-              paramId -= n;
-            }
-            while (paramId >= 0) {
-              m_stack.popTV();
-              paramId--;
-            }
-            m_stack.popAR();
-            tvWriteNull(retval);
-            return;
+          while (paramId >= 0) {
+            m_stack.popTV();
+            paramId--;
           }
+          m_stack.popAR();
+          tvWriteNull(retval);
+          return;
         }
       }
     }