Serializer: prepare support for INTERNAL_REFERENCE_ENCODED.

Platform ports that use this RelocInfo kind need to implement
set_target_internal_reference accordingly to distinguish between
INTERNAL_REFERENCE and INTERNAL_REFERENCE_ENCODED.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/1000373003

Cr-Commit-Position: refs/heads/master@{#27177}

src/assembler.cc

@@ -832,6 +832,8 @@ const char* RelocInfo::RelocModeName(RelocInfo::Mode rmode) {
       return "external reference";
     case RelocInfo::INTERNAL_REFERENCE:
       return "internal reference";
+    case RelocInfo::INTERNAL_REFERENCE_ENCODED:
+      return "encoded internal reference";
     case RelocInfo::DEOPT_REASON:
       return "deopt reason";
     case RelocInfo::CONST_POOL:
@@ -919,6 +921,7 @@ void RelocInfo::Verify(Isolate* isolate) {
     case STATEMENT_POSITION:
     case EXTERNAL_REFERENCE:
     case INTERNAL_REFERENCE:
+    case INTERNAL_REFERENCE_ENCODED:
     case DEOPT_REASON:
     case CONST_POOL:
     case VENEER_POOL:

src/assembler.h

@@ -379,6 +379,9 @@ class RelocInfo {
     EXTERNAL_REFERENCE,  // The address of an external C++ function.
     INTERNAL_REFERENCE,  // An address inside the same function.
 
+    // Encoded internal reference, used only on MIPS, MIPS64 and PPC.
+    INTERNAL_REFERENCE_ENCODED,
+
     // Marks constant and veneer pools. Only used on ARM and ARM64.
     // They use a custom noncompact encoding.
     CONST_POOL,
@@ -394,10 +397,6 @@ class RelocInfo {
     CODE_AGE_SEQUENCE,  // Not stored in RelocInfo array, used explictly by
                         // code aging.
 
-    // Encoded internal reference, used only on MIPS and MIPS64.
-    // Re-uses previous ARM-only encoding, to fit in RealRelocMode space.
-    INTERNAL_REFERENCE_ENCODED = CONST_POOL,
-
     FIRST_REAL_RELOC_MODE = CODE_TARGET,
     LAST_REAL_RELOC_MODE = VENEER_POOL,
     FIRST_PSEUDO_RELOC_MODE = CODE_AGE_SEQUENCE,

src/serialize.cc

@@ -799,7 +799,8 @@ void Deserializer::ReadObject(int space_number, Object** write_back) {
     // Turn internal references encoded as offsets back to absolute addresses.
     Code* code = Code::cast(obj);
     Address entry = code->entry();
-    int mode_mask = RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE);
+    int mode_mask = RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE) |
+                    RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE_ENCODED);
     for (RelocIterator it(code, mode_mask); !it.done(); it.next()) {
       RelocInfo* rinfo = it.rinfo();
       intptr_t offset =
@@ -1953,10 +1954,13 @@ Address Serializer::ObjectSerializer::PrepareCode() {
                   RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT) |
                   RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
                   RelocInfo::ModeMask(RelocInfo::RUNTIME_ENTRY) |
-                  RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE);
+                  RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE) |
+                  RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE_ENCODED);
   for (RelocIterator it(code, mode_mask); !it.done(); it.next()) {
     RelocInfo* rinfo = it.rinfo();
-    if (RelocInfo::IsInternalReference(rinfo->rmode())) {
+    RelocInfo::Mode rmode = rinfo->rmode();
+    if (RelocInfo::IsInternalReference(rmode) ||
+        RelocInfo::IsInternalReferenceEncoded(rmode)) {
       // Convert internal references to relative offsets.
       Address target = rinfo->target_internal_reference();
       intptr_t offset = target - entry;