Use a loop in generated code to allocate stack slots for function with many l...

src/x64/virtual-frame-x64.cc

Index: src/x64/virtual-frame-x64.cc
===================================================================
--- src/x64/virtual-frame-x64.cc	(revision 3519)
+++ src/x64/virtual-frame-x64.cc	(working copy)
@@ -129,11 +129,29 @@
     Handle<Object> undefined = Factory::undefined_value();
     FrameElement initial_value =
         FrameElement::ConstantElement(undefined, FrameElement::SYNCED);
-    __ movq(kScratchRegister, undefined, RelocInfo::EMBEDDED_OBJECT);
+    if (count == 1) {
+      __ Push(undefined);
+    } else if (count < kLocalVarBound) {
+      // For less locals the unrolled loop is more compact.
+      __ movq(kScratchRegister, undefined, RelocInfo::EMBEDDED_OBJECT);
+      for (int i = 0; i < count; i++) {
+        __ push(kScratchRegister);
+      }
+    } else {
+      // For more locals a loop in generated code is more compact.
+      Label alloc_locals_loop;
+      Result cnt = cgen()->allocator()->Allocate();
+      ASSERT(cnt.is_valid());
+      __ movq(cnt.reg(), Immediate(count));
+      __ movq(kScratchRegister, undefined, RelocInfo::EMBEDDED_OBJECT);
+      __ bind(&alloc_locals_loop);
+      __ push(kScratchRegister);
+      __ decl(cnt.reg());
+      __ j(not_zero, &alloc_locals_loop);
+    }
     for (int i = 0; i < count; i++) {
       elements_.Add(initial_value);
       stack_pointer_++;
-      __ push(kScratchRegister);
     }
   }
 }