[x86] Improve code generation for context materialization.

src/compiler/ia32/code-generator-ia32.cc

 // Copyright 2013 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/code-generator.h"
 
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/ia32/assembler-ia32.h"
@@ skipping 1101 matching lines @@
       __ mov(dst, src);
     } else {
       Operand dst = g.ToOperand(destination);
       __ push(src);
       __ pop(dst);
     }
   } else if (source->IsConstant()) {
     Constant src_constant = g.ToConstant(source);
     if (src_constant.type() == Constant::kHeapObject) {
       Handle<HeapObject> src = src_constant.ToHeapObject();
-      if (destination->IsRegister()) {
+      if (info()->IsOptimizing() && src.is_identical_to(info()->context())) {
+        // Loading the context from the frame is way cheaper than materializing
+        // the actual context heap object address.
+        if (destination->IsRegister()) {
+          Register dst = g.ToRegister(destination);
+          __ mov(dst, Operand(ebp, StandardFrameConstants::kContextOffset));
+        } else {
+          DCHECK(destination->IsStackSlot());
+          Operand dst = g.ToOperand(destination);
+          __ push(Operand(ebp, StandardFrameConstants::kContextOffset));
+          __ pop(dst);
+        }
+      } else if (destination->IsRegister()) {
         Register dst = g.ToRegister(destination);
         __ LoadHeapObject(dst, src);
       } else {
         DCHECK(destination->IsStackSlot());
         Operand dst = g.ToOperand(destination);
         AllowDeferredHandleDereference embedding_raw_address;
         if (isolate()->heap()->InNewSpace(*src)) {
           __ PushHeapObject(src);
           __ pop(dst);
         } else {
@@ skipping 139 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8