Debugger: use debug break slots to break at function exit.

src/ia32/assembler-ia32-inl.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 37 matching lines @@
 bool CpuFeatures::SupportsCrankshaft() { return true; }
 
 
 static const byte kCallOpcode = 0xE8;
 static const int kNoCodeAgeSequenceLength = 5;
 
 
 // The modes possibly affected by apply must be in kApplyMask.
 void RelocInfo::apply(intptr_t delta, ICacheFlushMode icache_flush_mode) {
   bool flush_icache = icache_flush_mode != SKIP_ICACHE_FLUSH;
+  int32_t* p;
   if (IsRuntimeEntry(rmode_) || IsCodeTarget(rmode_)) {
-    int32_t* p = reinterpret_cast<int32_t*>(pc_);
+    p = reinterpret_cast<int32_t*>(pc_);
     *p -= delta;  // Relocate entry.
-    if (flush_icache) CpuFeatures::FlushICache(p, sizeof(uint32_t));
   } else if (IsCodeAgeSequence(rmode_)) {
     if (*pc_ == kCallOpcode) {
       int32_t* p = reinterpret_cast<int32_t*>(pc_ + 1);
       *p -= delta;  // Relocate entry.
-    if (flush_icache) CpuFeatures::FlushICache(p, sizeof(uint32_t));
     }
-  } else if (IsJSReturn(rmode_) && IsPatchedReturnSequence()) {
-    // Special handling of js_return when a break point is set (call
-    // instruction has been inserted).
-    int32_t* p = reinterpret_cast<int32_t*>(pc_ + 1);
-    *p -= delta;  // Relocate entry.
-    if (flush_icache) CpuFeatures::FlushICache(p, sizeof(uint32_t));
   } else if (IsDebugBreakSlot(rmode_) && IsPatchedDebugBreakSlotSequence()) {
     // Special handling of a debug break slot when a break point is set (call
     // instruction has been inserted).
-    int32_t* p = reinterpret_cast<int32_t*>(pc_ + 1);
+    p = reinterpret_cast<int32_t*>(
+        pc_ + Assembler::kPatchDebugBreakSlotAddressOffset);
     *p -= delta;  // Relocate entry.
-    if (flush_icache) CpuFeatures::FlushICache(p, sizeof(uint32_t));
   } else if (IsInternalReference(rmode_)) {
     // absolute code pointer inside code object moves with the code object.
-    int32_t* p = reinterpret_cast<int32_t*>(pc_);
+    p = reinterpret_cast<int32_t*>(pc_);
     *p += delta;  // Relocate entry.
-    if (flush_icache) CpuFeatures::FlushICache(p, sizeof(uint32_t));
+  } else {
+    return;

[ulan, 2015/07/14 09:12:45]

I think it is cleaner to just set flush_icache to false.

[Yang, 2015/07/14 12:00:57]

apply is only ever called with SKIP_ICACHE_FLUSH. So I'm going to remove this
parameter and make this simpler. I added a comment to the function declaration.

Also icache_flush_mode is not even honored on ARM and ARM64.

   }
+  if (flush_icache) CpuFeatures::FlushICache(p, sizeof(uint32_t));
 }
 
 
 Address RelocInfo::target_address() {
   DCHECK(IsCodeTarget(rmode_) || IsRuntimeEntry(rmode_));
   return Assembler::target_address_at(pc_, host_);
 }
 
 
 Address RelocInfo::target_address_address() {
@@ skipping 141 matching lines @@
 
 void RelocInfo::set_code_age_stub(Code* stub,
                                   ICacheFlushMode icache_flush_mode) {
   DCHECK(*pc_ == kCallOpcode);
   DCHECK(rmode_ == RelocInfo::CODE_AGE_SEQUENCE);
   Assembler::set_target_address_at(pc_ + 1, host_, stub->instruction_start(),
                                    icache_flush_mode);
 }
 
 
-Address RelocInfo::call_address() {
-  DCHECK((IsJSReturn(rmode()) && IsPatchedReturnSequence()) ||
-         (IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence()));
-  return Assembler::target_address_at(pc_ + 1, host_);
+Address RelocInfo::debug_call_address() {
+  DCHECK(IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence());
+  Address location = pc_ + Assembler::kPatchDebugBreakSlotAddressOffset;
+  return Assembler::target_address_at(location, host_);
 }
 
 
-void RelocInfo::set_call_address(Address target) {
-  DCHECK((IsJSReturn(rmode()) && IsPatchedReturnSequence()) ||
-         (IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence()));
-  Assembler::set_target_address_at(pc_ + 1, host_, target);
+void RelocInfo::set_debug_call_address(Address target) {
+  DCHECK(IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence());
+  Address location = pc_ + Assembler::kPatchDebugBreakSlotAddressOffset;
+  Assembler::set_target_address_at(location, host_, target);
   if (host() != NULL) {
     Object* target_code = Code::GetCodeFromTargetAddress(target);
     host()->GetHeap()->incremental_marking()->RecordWriteIntoCode(
         host(), this, HeapObject::cast(target_code));
   }
 }
 
 
-Object* RelocInfo::call_object() {
-  return *call_object_address();
-}
-
-
-void RelocInfo::set_call_object(Object* target) {
-  *call_object_address() = target;
-}
-
-
-Object** RelocInfo::call_object_address() {
-  DCHECK((IsJSReturn(rmode()) && IsPatchedReturnSequence()) ||
-         (IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence()));
-  return reinterpret_cast<Object**>(pc_ + 1);
-}
-
-
 void RelocInfo::WipeOut() {
   if (IsEmbeddedObject(rmode_) || IsExternalReference(rmode_) ||
       IsInternalReference(rmode_)) {
     Memory::Address_at(pc_) = NULL;
   } else if (IsCodeTarget(rmode_) || IsRuntimeEntry(rmode_)) {
     // Effectively write zero into the relocation.
     Assembler::set_target_address_at(pc_, host_, pc_ + sizeof(int32_t));
   } else {
     UNREACHABLE();
   }
@@ skipping 18 matching lines @@
   } else if (RelocInfo::IsCodeTarget(mode)) {
     visitor->VisitCodeTarget(this);
   } else if (mode == RelocInfo::CELL) {
     visitor->VisitCell(this);
   } else if (mode == RelocInfo::EXTERNAL_REFERENCE) {
     visitor->VisitExternalReference(this);
   } else if (mode == RelocInfo::INTERNAL_REFERENCE) {
     visitor->VisitInternalReference(this);
   } else if (RelocInfo::IsCodeAgeSequence(mode)) {
     visitor->VisitCodeAgeSequence(this);
-  } else if (((RelocInfo::IsJSReturn(mode) &&
-              IsPatchedReturnSequence()) ||
-             (RelocInfo::IsDebugBreakSlot(mode) &&
-              IsPatchedDebugBreakSlotSequence())) &&
+  } else if (RelocInfo::IsDebugBreakSlot(mode) &&
+             IsPatchedDebugBreakSlotSequence() &&
              isolate->debug()->has_break_points()) {
     visitor->VisitDebugTarget(this);
   } else if (IsRuntimeEntry(mode)) {
     visitor->VisitRuntimeEntry(this);
   }
 }
 
 
 template<typename StaticVisitor>
 void RelocInfo::Visit(Heap* heap) {
   RelocInfo::Mode mode = rmode();
   if (mode == RelocInfo::EMBEDDED_OBJECT) {
     StaticVisitor::VisitEmbeddedPointer(heap, this);
     CpuFeatures::FlushICache(pc_, sizeof(Address));
   } else if (RelocInfo::IsCodeTarget(mode)) {
     StaticVisitor::VisitCodeTarget(heap, this);
   } else if (mode == RelocInfo::CELL) {
     StaticVisitor::VisitCell(heap, this);
   } else if (mode == RelocInfo::EXTERNAL_REFERENCE) {
     StaticVisitor::VisitExternalReference(this);
   } else if (mode == RelocInfo::INTERNAL_REFERENCE) {
     StaticVisitor::VisitInternalReference(this);
   } else if (RelocInfo::IsCodeAgeSequence(mode)) {
     StaticVisitor::VisitCodeAgeSequence(heap, this);
   } else if (heap->isolate()->debug()->has_break_points() &&
-             ((RelocInfo::IsJSReturn(mode) &&
-              IsPatchedReturnSequence()) ||
-             (RelocInfo::IsDebugBreakSlot(mode) &&
-              IsPatchedDebugBreakSlotSequence()))) {
+             RelocInfo::IsDebugBreakSlot(mode) &&
+             IsPatchedDebugBreakSlotSequence()) {
     StaticVisitor::VisitDebugTarget(heap, this);
   } else if (IsRuntimeEntry(mode)) {
     StaticVisitor::VisitRuntimeEntry(this);
   }
 }
 
 
 
 Immediate::Immediate(int x)  {
   x_ = x;
@@ skipping 131 matching lines @@
     CpuFeatures::FlushICache(p, sizeof(int32_t));
   }
 }
 
 
 Address Assembler::target_address_from_return_address(Address pc) {
   return pc - kCallTargetAddressOffset;
 }
 
 
-Address Assembler::break_address_from_return_address(Address pc) {
-  return pc - Assembler::kPatchDebugBreakSlotReturnOffset;
-}
-
-
 Displacement Assembler::disp_at(Label* L) {
   return Displacement(long_at(L->pos()));
 }
 
 
 void Assembler::disp_at_put(Label* L, Displacement disp) {
   long_at_put(L->pos(), disp.data());
 }
 
 
@@ skipping 73 matching lines @@
 
 
 Operand::Operand(Immediate imm) {
   // [disp/r]
   set_modrm(0, ebp);
   set_dispr(imm.x_, imm.rmode_);
 }
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_ASSEMBLER_IA32_INL_H_