Rename member variables and functions and clarify comments to try to...

src/codegen-ia32.cc

 // Copyright 2006-2008 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 1982 matching lines @@
   __ jmp(&exit);
 
 
   // --- Try block ---
   __ bind(&try_block);
 
   __ PushTryHandler(IN_JAVASCRIPT, TRY_CATCH_HANDLER);
   // TODO(1222589): remove the reliance of PushTryHandler on a cached TOS
   frame_->Push(eax);  //
 
-  // Introduce shadow labels for all escapes from the try block,
-  // including returns. We should probably try to unify the escaping
-  // labels and the return label.
+  // Shadow the labels for all escapes from the try block, including
+  // returns. During shadowing, the original label is hidden as the
+  // LabelShadow and operations on the original actually affect the
+  // shadowing label.
+  //
+  // We should probably try to unify the escaping labels and the return
+  // label.
   int nof_escapes = node->escaping_labels()->length();
   List<LabelShadow*> shadows(1 + nof_escapes);
   shadows.Add(new LabelShadow(&function_return_));
   for (int i = 0; i < nof_escapes; i++) {
     shadows.Add(new LabelShadow(node->escaping_labels()->at(i)));
   }
 
   // Generate code for the statements in the try block.
   bool was_inside_try = is_inside_try_;
   is_inside_try_ = true;
   VisitStatements(node->try_block()->statements());
   is_inside_try_ = was_inside_try;
 
   // Stop the introduced shadowing and count the number of required unlinks.
+  // After shadowing stops, the original labels are unshadowed and the
+  // LabelShadows represent the formerly shadowing labels.
   int nof_unlinks = 0;
   for (int i = 0; i <= nof_escapes; i++) {
     shadows[i]->StopShadowing();
     if (shadows[i]->is_linked()) nof_unlinks++;
   }
 
   // Get an external reference to the handler address.
   ExternalReference handler_address(Top::k_handler_address);
 
   // Make sure that there's nothing left on the stack above the
   // handler structure.
   if (FLAG_debug_code) {
     __ mov(eax, Operand::StaticVariable(handler_address));
     __ lea(eax, Operand(eax, StackHandlerConstants::kAddressDisplacement));
     __ cmp(esp, Operand(eax));
     __ Assert(equal, "stack pointer should point to top handler");
   }
 
   // Unlink from try chain.
   frame_->Pop(eax);
   __ mov(Operand::StaticVariable(handler_address), eax);  // TOS == next_sp
   frame_->Drop(StackHandlerConstants::kSize / kPointerSize - 1);
   // next_sp popped.
   if (nof_unlinks > 0) __ jmp(&exit);
 
-  // Generate unlink code for all used shadow labels.
+  // Generate unlink code for the (formerly) shadowing labels that have been
+  // jumped to.
   for (int i = 0; i <= nof_escapes; i++) {
     if (shadows[i]->is_linked()) {
       // Unlink from try chain; be careful not to destroy the TOS.
       __ bind(shadows[i]);
 
       // Reload sp from the top handler, because some statements that we
       // break from (eg, for...in) may have left stuff on the stack.
       __ mov(edx, Operand::StaticVariable(handler_address));
       const int kNextOffset = StackHandlerConstants::kNextOffset +
           StackHandlerConstants::kAddressDisplacement;
       __ lea(esp, Operand(edx, kNextOffset));
 
       frame_->Pop(Operand::StaticVariable(handler_address));
       frame_->Drop(StackHandlerConstants::kSize / kPointerSize - 1);
       // next_sp popped.
-      __ jmp(shadows[i]->shadowed());
+      __ jmp(shadows[i]->original_label());
     }
   }
 
   __ bind(&exit);
 }
 
 
 void CodeGenerator::VisitTryFinally(TryFinally* node) {
   Comment cmnt(masm_, "[ TryFinally");
 
@@ skipping 12 matching lines @@
   __ jmp(&finally_block);
 
 
   // --- Try block ---
   __ bind(&try_block);
 
   __ PushTryHandler(IN_JAVASCRIPT, TRY_FINALLY_HANDLER);
   // TODO(1222589): remove the reliance of PushTryHandler on a cached TOS
   frame_->Push(eax);
 
-  // Introduce shadow labels for all escapes from the try block,
-  // including returns. We should probably try to unify the escaping
-  // labels and the return label.
+  // Shadow the labels for all escapes from the try block, including
+  // returns. Shadowing hides the original label as the LabelShadow and
+  // operations on the original actually affect the shadowing label.
+  //
+  // We should probably try to unify the escaping labels and the return
+  // label.
   int nof_escapes = node->escaping_labels()->length();
   List<LabelShadow*> shadows(1 + nof_escapes);
   shadows.Add(new LabelShadow(&function_return_));
   for (int i = 0; i < nof_escapes; i++) {
     shadows.Add(new LabelShadow(node->escaping_labels()->at(i)));
   }
 
   // Generate code for the statements in the try block.
   bool was_inside_try = is_inside_try_;
   is_inside_try_ = true;
   VisitStatements(node->try_block()->statements());
   is_inside_try_ = was_inside_try;
 
-  // Stop the introduced shadowing and count the number of required
-  // unlinks.
+  // Stop the introduced shadowing and count the number of required unlinks.
+  // After shadowing stops, the original labels are unshadowed and the
+  // LabelShadows represent the formerly shadowing labels.
   int nof_unlinks = 0;
   for (int i = 0; i <= nof_escapes; i++) {
     shadows[i]->StopShadowing();
     if (shadows[i]->is_linked()) nof_unlinks++;
   }
 
   // Set the state on the stack to FALLING.
   frame_->Push(Immediate(Factory::undefined_value()));  // fake TOS
   __ Set(ecx, Immediate(Smi::FromInt(FALLING)));
   if (nof_unlinks > 0) __ jmp(&unlink);
 
-  // Generate code that sets the state for all used shadow labels.
+  // Generate code to set the state for the (formerly) shadowing labels that
+  // have been jumped to.
   for (int i = 0; i <= nof_escapes; i++) {
     if (shadows[i]->is_linked()) {
       __ bind(shadows[i]);
-      if (shadows[i]->shadowed() == &function_return_) {
-        // Materialize the return value on the stack.
+      if (shadows[i]->original_label() == &function_return_) {
+        // If this label shadowed the function return, materialize the
+        // return value on the stack.
         frame_->Push(eax);
       } else {
-        // Fake TOS for break and continue.
+        // Fake TOS for labels that shadowed breaks and continues.
         frame_->Push(Immediate(Factory::undefined_value()));
       }
       __ Set(ecx, Immediate(Smi::FromInt(JUMPING + i)));
       __ jmp(&unlink);
     }
   }
 
   // Unlink from try chain; be careful not to destroy the TOS.
   __ bind(&unlink);
   // Reload sp from the top handler, because some statements that we
@@ skipping 26 matching lines @@
   break_stack_height_ += kFinallyStackSize;
 
   // Generate code for the statements in the finally block.
   VisitStatements(node->finally_block()->statements());
 
   // Restore state and return value or faked TOS.
   frame_->Pop(ecx);
   frame_->Pop(eax);
   break_stack_height_ -= kFinallyStackSize;
 
-  // Generate code that jumps to the right destination for all used
-  // shadow labels.
+  // Generate code to jump to the right destination for all used (formerly)
+  // shadowing labels.
   for (int i = 0; i <= nof_escapes; i++) {
     if (shadows[i]->is_bound()) {
       __ cmp(Operand(ecx), Immediate(Smi::FromInt(JUMPING + i)));
-      __ j(equal, shadows[i]->shadowed());
+      __ j(equal, shadows[i]->original_label());
     }
   }
 
   // Check if we need to rethrow the exception.
   __ cmp(Operand(ecx), Immediate(Smi::FromInt(THROWING)));
   __ j(not_equal, &exit);
 
   // Rethrow exception.
   frame_->Push(eax);  // undo pop from above
   __ CallRuntime(Runtime::kReThrow, 1);
@@ skipping 2903 matching lines @@
 
   // Slow-case: Go through the JavaScript implementation.
   __ bind(&slow);
   __ InvokeBuiltin(Builtins::INSTANCE_OF, JUMP_FUNCTION);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal