Add PC descriptor for ret instruction

runtime/vm/code_generator_ia32.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/code_generator.h"
 
 #include "lib/error.h"
@@ skipping 739 matching lines @@
           Address::Absolute(Isolate::Current()->stack_limit_address()));
   Label no_stack_overflow;
   __ j(ABOVE, &no_stack_overflow);
   GenerateCallRuntime(AstNode::kNoId,
                       0,
                       kStackOverflowRuntimeEntry);
   __ Bind(&no_stack_overflow);
 }
 
 
-void CodeGenerator::GenerateReturnEpilog() {
+void CodeGenerator::GenerateReturnEpilog(ReturnNode* node) {
   // Unchain the context(s) up to context level 0.
   int context_level = state()->context_level();
   ASSERT(context_level >= 0);
   while (context_level-- > 0) {
     __ movl(CTX, FieldAddress(CTX, Context::parent_offset()));
   }
 #ifdef DEBUG
   // Check that the entry stack size matches the exit stack size.
   __ movl(EDX, EBP);
   __ subl(EDX, ESP);
@@ skipping 10 matching lines @@
     __ LoadObject(EBX, function);
     __ pushl(EBX);
     GenerateCallRuntime(AstNode::kNoId,
                         0,
                         kTraceFunctionExitRuntimeEntry);
     __ popl(EAX);  // Remove argument.
     __ popl(EAX);  // Restore result.
   }
   __ LeaveFrame();
   __ ret();
+  // Add a NOP to make return code pattern 5 bytes long for patching
+  // in breakpoints during debugging.

[srdjan, 2012/02/11 11:58:50]

Since we do not execute this code, would it make sense to add int3 instead?

[hausner, 2012/02/13 17:27:10]

If it isn't executed, it seems irrelevant whether it's NOP ir INT3. the nop
documents that it has no function other than take up space.

+  __ nop(1);
+  AddCurrentDescriptor(PcDescriptors::kReturn,
+                       AstNode::kNoId,

[srdjan, 2012/02/11 11:58:50]

Why not use return node id?

[hausner, 2012/02/13 17:27:10]

No particular reason. Will do in next change.

+                       node->token_index());
 
 #ifdef DEBUG
   __ Bind(&wrong_stack);
   __ Stop("Exit stack size does not match the entry stack size.");
 #endif  // DEBUG.
 }
 
 
 void CodeGenerator::VisitReturnNode(ReturnNode* node) {
   ASSERT(!IsResultNeeded(node));
@@ skipping 29 matching lines @@
     // Implicit getters do not need a type check at return.
     if ((kind != RawFunction::kImplicitGetter) &&
         (kind != RawFunction::kConstImplicitGetter)) {
       GenerateAssertAssignable(
           node->id(),
           node->value()->token_index(),
           AbstractType::ZoneHandle(parsed_function().function().result_type()),
           String::ZoneHandle(String::NewSymbol("function result")));
     }
   }
-  GenerateReturnEpilog();
+  GenerateReturnEpilog(node);
 }
 
 
 void CodeGenerator::VisitLiteralNode(LiteralNode* node) {
   if (!IsResultNeeded(node)) return;
   __ PushObject(node->literal());
 }
 
 
 void CodeGenerator::VisitTypeNode(TypeNode* node) {
@@ skipping 1938 matching lines @@
   const Error& error = Error::Handle(
       Parser::FormatError(script, token_index, "Error", format, args));
   va_end(args);
   Isolate::Current()->long_jump_base()->Jump(1, error);
   UNREACHABLE();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32