[compiler] Introduce a simple store-store elimination, disabled by default.

BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
@@ skipping 980 matching lines @@
     "src/compiler/simplified-lowering.cc",
     "src/compiler/simplified-lowering.h",
     "src/compiler/simplified-operator-reducer.cc",
     "src/compiler/simplified-operator-reducer.h",
     "src/compiler/simplified-operator.cc",
     "src/compiler/simplified-operator.h",
     "src/compiler/source-position.cc",
     "src/compiler/source-position.h",
     "src/compiler/state-values-utils.cc",
     "src/compiler/state-values-utils.h",
+    "src/compiler/store-store-elimination.cc",
+    "src/compiler/store-store-elimination.h",
     "src/compiler/tail-call-optimization.cc",
     "src/compiler/tail-call-optimization.h",
     "src/compiler/type-hint-analyzer.cc",
     "src/compiler/type-hint-analyzer.h",
     "src/compiler/type-hints.cc",
     "src/compiler/type-hints.h",
     "src/compiler/typer.cc",
     "src/compiler/typer.h",
     "src/compiler/value-numbering-reducer.cc",
     "src/compiler/value-numbering-reducer.h",
@@ skipping 1303 matching lines @@
 
   deps = [
     ":fuzzer_support",
   ]
 
   configs = [ ":internal_config" ]
 }
 
 v8_fuzzer("wasm_asmjs_fuzzer") {
 }