[x86] Improve code generation for context materialization.

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

Index: src/compiler/ia32/code-generator-ia32.cc
diff --git a/src/compiler/ia32/code-generator-ia32.cc b/src/compiler/ia32/code-generator-ia32.cc
index 7864d90a82672afc5c866125db897eb6b0b3f12c..3cb3d40539ca7a9e6e1a43d6275d86f6397a4277 100644
--- a/src/compiler/ia32/code-generator-ia32.cc
+++ b/src/compiler/ia32/code-generator-ia32.cc
@@ -1119,7 +1119,19 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
     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 {