Clean up dead code after spread desugaring

src/full-codegen/mips64/full-codegen-mips64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_MIPS64
 
 // Note on Mips implementation:
 //
 // The result_register() for mips is the 'v0' register, which is defined
 // by the ABI to contain function return values. However, the first
@@ skipping 1698 matching lines @@
 
   bool result_saved = false;  // Is the result saved to the stack?
   ZoneList<Expression*>* subexprs = expr->values();
   int length = subexprs->length();
 
   // Emit code to evaluate all the non-constant subexpressions and to store
   // them into the newly cloned array.
   int array_index = 0;
   for (; array_index < length; array_index++) {
     Expression* subexpr = subexprs->at(array_index);
-    if (subexpr->IsSpread()) break;
+    DCHECK(!subexpr->IsSpread());
 
     // If the subexpression is a literal or a simple materialized literal it
     // is already set in the cloned array.
     if (CompileTimeValue::IsCompileTimeValue(subexpr)) continue;
 
     if (!result_saved) {
       __ push(v0);  // array literal
       result_saved = true;
     }
 
@@ skipping 16 matching lines @@
   // (inclusive) and these elements gets appended to the array. Note that the
   // number elements an iterable produces is unknown ahead of time.
   if (array_index < length && result_saved) {
     __ Pop(v0);
     result_saved = false;
   }
   for (; array_index < length; array_index++) {
     Expression* subexpr = subexprs->at(array_index);
 
     __ Push(v0);
-    if (subexpr->IsSpread()) {
-      VisitForStackValue(subexpr->AsSpread()->expression());
-      __ InvokeBuiltin(Context::CONCAT_ITERABLE_TO_ARRAY_BUILTIN_INDEX,
-                       CALL_FUNCTION);
-    } else {
-      VisitForStackValue(subexpr);
-      __ CallRuntime(Runtime::kAppendElement);
-    }
+    DCHECK(!subexpr->IsSpread());
+    VisitForStackValue(subexpr);
+    __ CallRuntime(Runtime::kAppendElement);
 
     PrepareForBailoutForId(expr->GetIdForElement(array_index), NO_REGISTERS);
   }
 
   if (result_saved) {
     context()->PlugTOS();
   } else {
     context()->Plug(v0);
   }
 }
@@ skipping 3071 matching lines @@
          reinterpret_cast<uint64_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS64