[turbofan] Rework handling of loop exits in loop peeling.

src/compiler/loop-analysis.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/loop-analysis.h"
 
 #include "src/compiler/graph.h"
 #include "src/compiler/node.h"
 #include "src/compiler/node-marker.h"
 #include "src/compiler/node-properties.h"
 #include "src/zone.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 #define OFFSET(x) ((x)&0x1f)
 #define BIT(x) (1u << OFFSET(x))
 #define INDEX(x) ((x) >> 5)
 
-// TODO(titzer): don't assume entry edges have a particular index.
-static const int kAssumedLoopEntryIndex = 0;  // assume loops are entered here.
-
-
 // Temporary information for each node during marking.
 struct NodeInfo {
   Node* node;
   NodeInfo* next;       // link in chaining loop members
 };
 
 
 // Temporary loop info needed during traversal and building the loop tree.
 struct LoopInfo {
   Node* header;
@@ skipping 433 matching lines @@
   if (first->opcode() == IrOpcode::kLoop) return first;
   DCHECK(IrOpcode::IsPhiOpcode(first->opcode()));
   Node* header = NodeProperties::GetControlInput(first);
   DCHECK_EQ(IrOpcode::kLoop, header->opcode());
   return header;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8