Add code comments to inline cache stubs.

runtime/vm/stub_code_ia32.cc

 // Copyright (c) 2013, 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"
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 1172 matching lines @@
 
 
 // Note: ECX must be preserved.
 // Attempt a quick Smi operation for known operations ('kind'). The ICData
 // must have been primed with a Smi/Smi check that will be used for counting
 // the invocations.
 static void EmitFastSmiOp(Assembler* assembler,
                           Token::Kind kind,
                           intptr_t num_args,
                           Label* not_smi_or_overflow) {
+  __ Comment("Fast Smi op");
   ASSERT(num_args == 2);
   __ movl(EDI, Address(ESP, + 1 * kWordSize));  // Right
   __ movl(EAX, Address(ESP, + 2 * kWordSize));  // Left
   __ movl(EBX, EDI);
   __ orl(EBX, EAX);
   __ testl(EBX, Immediate(kSmiTagMask));
   __ j(NOT_ZERO, not_smi_or_overflow, Assembler::kNearJump);
   switch (kind) {
     case Token::kADD: {
       __ addl(EAX, EDI);
@@ skipping 78 matching lines @@
     __ movl(EBX, FieldAddress(ECX, ICData::state_bits_offset()));
     ASSERT(ICData::NumArgsTestedShift() == 0);  // No shift needed.
     __ andl(EBX, Immediate(ICData::NumArgsTestedMask()));
     __ cmpl(EBX, Immediate(num_args));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Incorrect stub for IC data");
     __ Bind(&ok);
   }
 #endif  // DEBUG
 
-  // Check single stepping.
+  __ Comment("Check single stepping");
   Label stepping, done_stepping;
   uword single_step_address = reinterpret_cast<uword>(Isolate::Current()) +
       Isolate::single_step_offset();
   __ cmpb(Address::Absolute(single_step_address), Immediate(0));
   __ j(NOT_EQUAL, &stepping);
   __ Bind(&done_stepping);
 
+  __ Comment("Range feedback collection");
   Label not_smi_or_overflow;
   if (range_collection_mode == kCollectRanges) {
     ASSERT((num_args == 1) || (num_args == 2));
     if (num_args == 2) {
       __ movl(EAX, Address(ESP, + 2 * kWordSize));
       __ UpdateRangeFeedback(EAX, 0, ECX, EBX, EDI, ESI, &not_smi_or_overflow);
     }
 
     __ movl(EAX, Address(ESP, + 1 * kWordSize));
     __ UpdateRangeFeedback(EAX, (num_args - 1), ECX, EBX, EDI, ESI,
                            &not_smi_or_overflow);
   }
   if (kind != Token::kILLEGAL) {
     EmitFastSmiOp(assembler, kind, num_args, &not_smi_or_overflow);
   }
   __ Bind(&not_smi_or_overflow);
 
+  __ Comment("Extract ICData initial values and receiver cid");
   // ECX: IC data object (preserved).
   // Load arguments descriptor into EDX.
   __ movl(EDX, FieldAddress(ECX, ICData::arguments_descriptor_offset()));
   // Loop that checks if there is an IC data match.
-  Label loop, update, test, found;
   // ECX: IC data object (preserved).
   __ movl(EBX, FieldAddress(ECX, ICData::ic_data_offset()));
   // EBX: ic_data_array with check entries: classes and target functions.
   __ leal(EBX, FieldAddress(EBX, Array::data_offset()));
   // EBX: points directly to the first ic data array element.
 
   // Get the receiver's class ID (first read number of arguments from
   // arguments descriptor array and then access the receiver from the stack).
   __ movl(EAX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
   __ movl(EDI, Address(ESP, EAX, TIMES_2, 0));  // EAX (argument_count) is smi.
   __ LoadTaggedClassIdMayBeSmi(EAX, EDI);
 
   // EAX: receiver's class ID (smi).
   __ movl(EDI, Address(EBX, 0));  // First class id (smi) to check.
+  Label loop, update, test, found;
   __ jmp(&test);
 
+  __ Comment("ICData loop");
   __ Bind(&loop);
   for (int i = 0; i < num_args; i++) {
     if (i > 0) {
       // If not the first, load the next argument's class ID.
       __ movl(EAX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
       __ movl(EDI, Address(ESP, EAX, TIMES_2, - i * kWordSize));
       __ LoadTaggedClassIdMayBeSmi(EAX, EDI);
 
       // EAX: next argument class ID (smi).
       __ movl(EDI, Address(EBX, i * kWordSize));
@@ skipping 16 matching lines @@
   }
 
   const intptr_t entry_size = ICData::TestEntryLengthFor(num_args) * kWordSize;
   __ addl(EBX, Immediate(entry_size));  // Next entry.
   __ movl(EDI, Address(EBX, 0));  // Next class ID.
 
   __ Bind(&test);
   __ cmpl(EDI, Immediate(Smi::RawValue(kIllegalCid)));  // Done?
   __ j(NOT_EQUAL, &loop, Assembler::kNearJump);
 
-  // IC miss.
+  __ Comment("IC miss");
   const Immediate& raw_null =
       Immediate(reinterpret_cast<intptr_t>(Object::null()));
   // Compute address of arguments (first read number of arguments from
   // arguments descriptor array and then compute address on the stack).
   __ movl(EAX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
   __ leal(EAX, Address(ESP, EAX, TIMES_2, 0));  // EAX is Smi.
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame();
   __ pushl(EDX);  // Preserve arguments descriptor array.
@@ skipping 11 matching lines @@
     __ popl(EAX);
   }
   __ popl(EAX);  // Pop returned function object into EAX.
   __ popl(ECX);  // Restore IC data array.
   __ popl(EDX);  // Restore arguments descriptor array.
   __ LeaveFrame();
   Label call_target_function;
   __ jmp(&call_target_function);
 
   __ Bind(&found);
+
   // EBX: Pointer to an IC data check group.
   const intptr_t target_offset = ICData::TargetIndexFor(num_args) * kWordSize;
   const intptr_t count_offset = ICData::CountIndexFor(num_args) * kWordSize;
 
-  // Update counter.
+  __ Comment("Update caller's counter");
   __ movl(EAX, Address(EBX, count_offset));
   __ addl(EAX, Immediate(Smi::RawValue(1)));
   __ movl(EDI, Immediate(Smi::RawValue(Smi::kMaxValue)));
   __ cmovno(EDI, EAX);
   __ StoreIntoSmiField(Address(EBX, count_offset), EDI);
 
   __ movl(EAX, Address(EBX, target_offset));
   __ Bind(&call_target_function);
+  __ Comment("Call target");
   // EAX: Target function.
   __ movl(EBX, FieldAddress(EAX, Function::instructions_offset()));
   __ addl(EBX, Immediate(Instructions::HeaderSize() - kHeapObjectTag));
   if (range_collection_mode == kCollectRanges) {
     __ movl(EDI, Address(ESP, + 1 * kWordSize));
     if (num_args == 2) {
       __ movl(ESI, Address(ESP, + 2 * kWordSize));
     }
     __ EnterStubFrame();
     __ pushl(ECX);
@@ skipping 604 matching lines @@
   const Register temp = ECX;
   __ movl(left, Address(ESP, 2 * kWordSize));
   __ movl(right, Address(ESP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32