Simplify Hydrogen code stubs with variable argument count

src/deoptimizer.cc

 // Copyright 2013 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 1520 matching lines @@
   value = frame_ptr + StandardFrameConstants::kCallerSPOffset -
       (output_frame_size - output_frame_offset) + kPointerSize;
   output_frame->SetFrameSlot(output_frame_offset, value);
   if (trace_) {
     PrintF("    0x%08" V8PRIxPTR ": [top + %d] <- 0x%08"
            V8PRIxPTR " ; args*\n",
            top_address + output_frame_offset, output_frame_offset, value);
   }
 
   // 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);
 
   // Fill registers containing handler and number of parameters.
   SetPlatformCompiledStubRegisters(output_frame, descriptor);
 
   // Compute this frame's PC, state, and continuation.
   Code* trampoline = NULL;
   StubFunctionMode function_mode = descriptor->function_mode_;
   StubFailureTrampolineStub(function_mode).FindCodeInCache(&trampoline,
@@ skipping 1376 matching lines @@
 
 void DeoptimizedFrameInfo::Iterate(ObjectVisitor* v) {
   v->VisitPointer(BitCast<Object**>(&function_));
   v->VisitPointers(parameters_, parameters_ + parameters_count_);
   v->VisitPointers(expression_stack_, expression_stack_ + expression_count_);
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal