Clean up dead code after spread desugaring

src/compiler/ast-graph-builder.cc

 // Copyright 2014 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.
 
 #include "src/compiler/ast-graph-builder.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
@@ skipping 1919 matching lines @@
 
   // The array is expected on the operand stack during computation of the
   // element values.
   environment()->Push(literal);
 
   // Create nodes to evaluate all the non-constant subexpressions and to store
   // them into the newly cloned array.
   int array_index = 0;
   for (; array_index < expr->values()->length(); array_index++) {
     Expression* subexpr = expr->values()->at(array_index);
-    if (subexpr->IsSpread()) break;
+    DCHECK(!subexpr->IsSpread());
     if (CompileTimeValue::IsCompileTimeValue(subexpr)) continue;
 
     VisitForValue(subexpr);
     {
       FrameStateBeforeAndAfter states(this, subexpr->id());
       VectorSlotPair pair = CreateVectorSlotPair(expr->LiteralFeedbackSlot());
       Node* value = environment()->Pop();
       Node* index = jsgraph()->Constant(array_index);
       Node* literal = environment()->Top();
       Node* store = BuildKeyedStore(literal, index, value, pair);
       states.AddToNode(store, expr->GetIdForElement(array_index),
                        OutputFrameStateCombine::Ignore());
     }
   }
 
   // In case the array literal contains spread expressions it has two parts. The
   // first part is  the "static" array which has a literal index is handled
   // above. The second part is the part after the first spread expression
   // (inclusive) and these elements gets appended to the array. Note that the
   // number elements an iterable produces is unknown ahead of time.
   for (; array_index < expr->values()->length(); array_index++) {
     Expression* subexpr = expr->values()->at(array_index);
-    Node* result;
+    DCHECK(!subexpr->IsSpread());
 
-    if (subexpr->IsSpread()) {
-      VisitForValue(subexpr->AsSpread()->expression());
-      FrameStateBeforeAndAfter states(this,
-                                      subexpr->AsSpread()->expression()->id());
-      Node* iterable = environment()->Pop();
-      Node* array = environment()->Pop();
-      Node* function = BuildLoadNativeContextField(
-          Context::CONCAT_ITERABLE_TO_ARRAY_BUILTIN_INDEX);
-      result = NewNode(javascript()->CallFunction(3, language_mode()), function,
-                       array, iterable);
-      states.AddToNode(result, expr->GetIdForElement(array_index));
-    } else {
-      VisitForValue(subexpr);
+    VisitForValue(subexpr);
+    {
       Node* value = environment()->Pop();
       Node* array = environment()->Pop();
       const Operator* op = javascript()->CallRuntime(Runtime::kAppendElement);
-      result = NewNode(op, array, value);
+      Node* result = NewNode(op, array, value);
       PrepareFrameState(result, expr->GetIdForElement(array_index));
+      environment()->Push(result);
     }
-
-    environment()->Push(result);
   }
 
   ast_context()->ProduceValue(environment()->Pop());
 }
 
 
 void AstGraphBuilder::VisitForInAssignment(Expression* expr, Node* value,
                                            const VectorSlotPair& feedback,
                                            BailoutId bailout_id_before,
                                            BailoutId bailout_id_after) {
@@ skipping 2354 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8