[turbofan] Allow for 32-bit field offsets in store elimination.

src/compiler/store-store-elimination.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 <iterator>
 
 #include "src/compiler/store-store-elimination.h"
 
 #include "src/compiler/all-nodes.h"
 #include "src/compiler/js-graph.h"
@@ skipping 54 matching lines @@
 // Assumption: every byte of a JS object is only ever accessed through one
 // offset. For instance, byte 15 of a given object may be accessed using a
 // two-byte read at offset 14, or a four-byte read at offset 12, but never
 // both in the same program.
 //
 // This implementation needs all dead nodes removed from the graph, and the
 // graph should be trimmed.
 
 namespace {
 
-// 16 bits was chosen fairly arbitrarily; it seems enough now. 8 bits is too
-// few.
-typedef uint16_t StoreOffset;
+typedef uint32_t StoreOffset;
 
 struct UnobservableStore {
   NodeId id_;
   StoreOffset offset_;
 
   bool operator==(const UnobservableStore) const;
   bool operator!=(const UnobservableStore) const;
   bool operator<(const UnobservableStore) const;
 };
 
@@ skipping 76 matching lines @@
   Zone* const temp_zone_;
 
   ZoneStack<Node*> revisit_;
   ZoneVector<bool> in_revisit_;
   // Maps node IDs to UnobservableNodeSets.
   ZoneVector<UnobservablesSet> unobservable_;
   ZoneSet<Node*> to_remove_;
   const UnobservablesSet unobservables_visited_empty_;
 };
 
-// To safely cast an offset from a FieldAccess, which has a wider range
-// (namely int).
+// To safely cast an offset from a FieldAccess, which has a potentially wider
+// range (namely int).
 StoreOffset ToOffset(int offset) {
-  CHECK(0 <= offset && offset < (1 << 8 * sizeof(StoreOffset)));
-  return (StoreOffset)offset;
+  CHECK(0 <= offset);
+  return static_cast<StoreOffset>(offset);
 }
 
 StoreOffset ToOffset(const FieldAccess& access) {
   return ToOffset(access.offset);
 }
 
 unsigned int RepSizeOf(MachineRepresentation rep) {
   return 1u << ElementSizeLog2Of(rep);
 }
 unsigned int RepSizeOf(FieldAccess access) {
@@ skipping 372 matching lines @@
   return !(*this == other);
 }
 
 bool UnobservableStore::operator<(const UnobservableStore other) const {
   return (id_ < other.id_) || (id_ == other.id_ && offset_ < other.offset_);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8