[ptr-compr] Make Code serialization pointer compression friendly

Bug: v8:7703
Change-Id: I47e6971bc99186cb6861164ec2a246ebcd770219
Reviewed-on: https://chromium-review.googlesource.com/c/1349230Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57780}

src/objects/code-inl.h

@@ -322,8 +322,7 @@ byte* Code::relocation_start() const {
 }
 
 byte* Code::relocation_end() const {
-  return unchecked_relocation_info()->GetDataStartAddress() +
-         unchecked_relocation_info()->length();
+  return unchecked_relocation_info()->GetDataEndAddress();
 }
 
 int Code::relocation_size() const {

src/objects/fixed-array-inl.h

@@ -487,6 +487,10 @@ byte* ByteArray::GetDataStartAddress() {
   return reinterpret_cast<byte*>(address() + kHeaderSize);
 }
 
+byte* ByteArray::GetDataEndAddress() {
+  return GetDataStartAddress() + length();
+}
+
 template <class T>
 PodArray<T>* PodArray<T>::cast(Object* object) {
   DCHECK(object->IsByteArray());

src/objects/fixed-array.h

@@ -645,6 +645,8 @@ class ByteArray : public FixedArrayBase {
 
   // Returns data start address.
   inline byte* GetDataStartAddress();
+  // Returns address of the past-the-end element.
+  inline byte* GetDataEndAddress();
 
   inline int DataSize() const;
 

src/reloc-info.cc

@@ -281,9 +281,13 @@ void RelocIterator::next() {
 }
 
 RelocIterator::RelocIterator(Code code, int mode_mask)
+    : RelocIterator(code, code->unchecked_relocation_info(), mode_mask) {}
+
+RelocIterator::RelocIterator(Code code, ByteArray* relocation_info,
+                             int mode_mask)
     : RelocIterator(code, code->raw_instruction_start(), code->constant_pool(),
-                    code->relocation_end(), code->relocation_start(),
-                    mode_mask) {}
+                    relocation_info->GetDataEndAddress(),
+                    relocation_info->GetDataStartAddress(), mode_mask) {}
 
 RelocIterator::RelocIterator(const CodeReference code_reference, int mode_mask)
     : RelocIterator(Code(), code_reference.instruction_start(),

src/reloc-info.h

@@ -382,6 +382,7 @@ class RelocIterator : public Malloced {
   // Relocation information with mode k is included in the
   // iteration iff bit k of mode_mask is set.
   explicit RelocIterator(Code code, int mode_mask = -1);
+  explicit RelocIterator(Code code, ByteArray* relocation_info, int mode_mask);
   explicit RelocIterator(EmbeddedData* embedded_data, Code code, int mode_mask);
   explicit RelocIterator(const CodeDesc& desc, int mode_mask = -1);
   explicit RelocIterator(const CodeReference code_reference,

src/snapshot/serializer.cc

@@ -926,10 +926,10 @@ int Serializer::ObjectSerializer::SkipTo(Address to) {
 
 void Serializer::ObjectSerializer::OutputCode(int size) {
   DCHECK_EQ(kPointerSize, bytes_processed_so_far_);
-  Code code = Code::cast(object_);
+  Code on_heap_code = Code::cast(object_);
   // To make snapshots reproducible, we make a copy of the code object
   // and wipe all pointers in the copy, which we then serialize.
-  code = serializer_->CopyCode(code);
+  Code off_heap_code = serializer_->CopyCode(on_heap_code);
   int mode_mask = RelocInfo::ModeMask(RelocInfo::CODE_TARGET) |
                   RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT) |
                   RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
@@ -937,15 +937,20 @@ void Serializer::ObjectSerializer::OutputCode(int size) {
                   RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE_ENCODED) |
                   RelocInfo::ModeMask(RelocInfo::OFF_HEAP_TARGET) |
                   RelocInfo::ModeMask(RelocInfo::RUNTIME_ENTRY);
-  for (RelocIterator it(code, mode_mask); !it.done(); it.next()) {
+  // With enabled pointer compression normal accessors no longer work for
+  // off-heap objects, so we have to get the relocation info data via the
+  // on-heap code object.
+  ByteArray* relocation_info = on_heap_code->unchecked_relocation_info();
+  for (RelocIterator it(off_heap_code, relocation_info, mode_mask); !it.done();
+       it.next()) {
     RelocInfo* rinfo = it.rinfo();
     rinfo->WipeOut();
   }
   // We need to wipe out the header fields *after* wiping out the
   // relocations, because some of these fields are needed for the latter.
-  code->WipeOutHeader();
+  off_heap_code->WipeOutHeader();
 
-  Address start = code->address() + Code::kDataStart;
+  Address start = off_heap_code->address() + Code::kDataStart;
   int bytes_to_output = size - Code::kDataStart;
 
   sink_->Put(kVariableRawCode, "VariableRawCode");