[csa] Return last value from BuildFastLoop to allow chaining sequential loops

src/code-stub-assembler.cc

 // Copyright 2016 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/code-stub-assembler.h"
 #include "src/code-factory.h"
 #include "src/frames-inl.h"
 #include "src/frames.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 6232 matching lines @@
   StoreObjectField(cell, WeakCell::kValueOffset, value);
   StoreObjectFieldRoot(cell, WeakCell::kNextOffset,
                        Heap::kTheHoleValueRootIndex);
 
   // Store the WeakCell in the feedback vector.
   StoreFixedArrayElement(feedback_vector, slot, cell, UPDATE_WRITE_BARRIER, 0,
                          CodeStubAssembler::SMI_PARAMETERS);
   return cell;
 }
 
-void CodeStubAssembler::BuildFastLoop(
+Node* CodeStubAssembler::BuildFastLoop(
     const CodeStubAssembler::VariableList& vars,
     MachineRepresentation index_rep, Node* start_index, Node* end_index,
     const FastLoopBody& body, int increment, IndexAdvanceMode mode) {
   Variable var(this, index_rep, start_index);
   VariableList vars_copy(vars, zone());
   vars_copy.Add(&var, zone());
   Label loop(this, vars_copy);
   Label after_loop(this);
   // Introduce an explicit second check of the termination condition before the
   // loop that helps turbofan generate better code. If there's only a single
   // check, then the CodeStubAssembler forces it to be at the beginning of the
   // loop requiring a backwards branch at the end of the loop (it's not possible
   // to force the loop header check at the end of the loop and branch forward to
   // it from the pre-header). The extra branch is slower in the case that the
   // loop actually iterates.
   Branch(WordEqual(var.value(), end_index), &after_loop, &loop);
   Bind(&loop);
   {
     if (mode == IndexAdvanceMode::kPre) {
       Increment(var, increment);
     }
     body(var.value());
     if (mode == IndexAdvanceMode::kPost) {
       Increment(var, increment);
     }
     Branch(WordNotEqual(var.value(), end_index), &loop, &after_loop);
   }
   Bind(&after_loop);
+  return var.value();
 }
 
 void CodeStubAssembler::BuildFastFixedArrayForEach(
     Node* fixed_array, ElementsKind kind, Node* first_element_inclusive,
     Node* last_element_exclusive, const FastFixedArrayForEachBody& body,
     ParameterMode mode, ForEachDirection direction) {
   STATIC_ASSERT(FixedArray::kHeaderSize == FixedDoubleArray::kHeaderSize);
   int32_t first_val;
   bool constant_first = ToInt32Constant(first_element_inclusive, first_val);
   int32_t last_val;
@@ skipping 2096 matching lines @@
         formatted.c_str(), TENURED);
     CallRuntime(Runtime::kGlobalPrint, NoContextConstant(),
                 HeapConstant(string));
   }
   CallRuntime(Runtime::kGlobalPrint, NoContextConstant(), tagged_value);
 #endif
 }
 
 }  // namespace internal
 }  // namespace v8