Simplify Hydrogen code stubs with variable argument count

src/deoptimizer.cc

Index: src/deoptimizer.cc
diff --git a/src/deoptimizer.cc b/src/deoptimizer.cc
index 96871d610f48d09f367d30d56149d6001aaa3d95..f72157d2532017dc69db79d922a3c3c078e9b746 100644
--- a/src/deoptimizer.cc
+++ b/src/deoptimizer.cc
@@ -1538,27 +1538,44 @@ void Deoptimizer::DoComputeCompiledStubFrame(TranslationIterator* iterator,
   }
 
   // Copy the register parameters to the failure frame.
+  int arguments_length_offset = -1;
   for (int i = 0; i < descriptor->register_param_count_; ++i) {
     output_frame_offset -= kPointerSize;
     DoTranslateCommand(iterator, 0, output_frame_offset);
+
+    if (!arg_count_known && descriptor->IsParameterCountRegister(i)) {
+      arguments_length_offset = output_frame_offset;
+    }
   }
 
+  ASSERT(0 == output_frame_offset);
+
   if (!arg_count_known) {
-    DoTranslateCommand(iterator, 0, length_frame_offset,
-                       TRANSLATED_VALUE_IS_NATIVE);

[Toon Verwaest, 2013/11/12 15:43:06]

Now we can get rid of TRANSLATED_VALUE_IS_NATIVE I think.

-    caller_arg_count = output_frame->GetFrameSlot(length_frame_offset);
+    ASSERT(arguments_length_offset >= 0);
+    // We know it's a smi because 1) the code stub guarantees the stack
+    // parameter count is in smi range, and 2) the DoTranslateCommand in the
+    // parameter loop above translated that to a tagged value.
+    Smi* smi_caller_arg_count = reinterpret_cast<Smi*>(
+        output_frame->GetFrameSlot(arguments_length_offset));
+    caller_arg_count = smi_caller_arg_count->value();
+    output_frame->SetFrameSlot(length_frame_offset, caller_arg_count);
+    if (trace_) {
+      PrintF("    0x%08" V8PRIxPTR ": [top + %d] <- 0x%08"
+             V8PRIxPTR " ; args.length\n",
+             top_address + length_frame_offset, length_frame_offset,
+             caller_arg_count);
+    }
     value = frame_ptr + StandardFrameConstants::kCallerSPOffset +
         (caller_arg_count - 1) * kPointerSize;
     output_frame->SetFrameSlot(args_arguments_offset, value);
     if (trace_) {
       PrintF("    0x%08" V8PRIxPTR ": [top + %d] <- 0x%08"
              V8PRIxPTR " ; args.arguments\n",
-             top_address + args_arguments_offset, args_arguments_offset, value);
+             top_address + args_arguments_offset, args_arguments_offset,
+             value);
     }
   }
 
-  ASSERT(0 == output_frame_offset);
-
   // Copy the double registers from the input into the output frame.
   CopyDoubleRegisters(output_frame);