[wasm] Add guard regions to end of WebAssembly.Memory buffers

src/compiler/wasm-compiler.cc

 // Copyright 2015 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/wasm-compiler.h"
 
 #include <memory>
 
 #include "src/isolate-inl.h"
 
@@ skipping 2952 matching lines @@
   // WASM semantics throw on OOB. Introduce explicit bounds check.
   if (!FLAG_wasm_trap_handler) {
     BoundsCheckMem(memtype, index, offset, position);
   }
   bool aligned = static_cast<int>(alignment) >=
                  ElementSizeLog2Of(memtype.representation());
 
   if (aligned ||
       jsgraph()->machine()->UnalignedLoadSupported(memtype, alignment)) {
     if (FLAG_wasm_trap_handler) {
+      DCHECK(FLAG_wasm_guard_pages);

[titzer, 2016/11/09 19:23:47]

Generally want to avoid DCHECK'ing flags IMO.

       Node* context = HeapConstant(module_->instance->context);
       Node* position_node = jsgraph()->Int32Constant(position);
       load = graph()->NewNode(jsgraph()->machine()->ProtectedLoad(memtype),
                               MemBuffer(offset), index, context, position_node,
                               *effect_, *control_);
     } else {
       load = graph()->NewNode(jsgraph()->machine()->Load(memtype),
                               MemBuffer(offset), index, *effect_, *control_);
     }
   } else {
@@ skipping 512 matching lines @@
                             function_->code_start_offset),
            compile_ms);
   }
 
   return code;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8