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

src/x64/virtual-frame-x64.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 111 matching lines @@
   if (count > 0) {
     Comment cmnt(masm(), "[ Allocate space for locals");
     // The locals are initialized to a constant (the undefined value), but
     // we sync them with the actual frame to allocate space for spilling
     // them later.  First sync everything above the stack pointer so we can
     // use pushes to allocate and initialize the locals.
     SyncRange(stack_pointer_ + 1, element_count() - 1);
     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);
     }
   }
 }
 
 
 void VirtualFrame::SaveContextRegister() {
   ASSERT(elements_[context_index()].is_memory());
   __ movq(Operand(rbp, fp_relative(context_index())), rsi);
 }
 
@@ skipping 915 matching lines @@
   // Grow the expression stack by handler size less one (the return
   // address is already pushed by a call instruction).
   Adjust(kHandlerSize - 1);
   __ PushTryHandler(IN_JAVASCRIPT, type);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal