Externalize deoptimization reasons.

src/assembler.cc

 // 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 310 matching lines @@
 const int kLastChunkTag = 1;
 
 
 const int kDataJumpExtraTag = kPCJumpExtraTag - 1;
 
 const int kCodeWithIdTag = 0;
 const int kNonstatementPositionTag = 1;
 const int kStatementPositionTag = 2;
 const int kCommentTag = 3;
 
+// Reuse the same value for deopt reason tag in short record format.

[Michael Starzinger, 2015/02/04 11:30:51]

IIUC, this assumes that comments are always encoded in "long format" and deopt
reasons are always encoded in "short format". Correct? Can we make this explicit
in this comment?

[loislo, 2015/02/04 14:38:49]

done

+const int kDeoptReasonTag = 3;
+
 const int kPoolExtraTag = kPCJumpExtraTag - 2;
 const int kConstPoolTag = 0;
 const int kVeneerPoolTag = 1;
 
 
 uint32_t RelocInfoWriter::WriteVariableLengthPCJump(uint32_t pc_delta) {
   // Return if the pc_delta can fit in kSmallPCDeltaBits bits.
   // Otherwise write a variable length PC jump for the bits that do
   // not fit in the kSmallPCDeltaBits bits.
   if (is_uintn(pc_delta, kSmallPCDeltaBits)) return pc_delta;
@@ skipping 75 matching lines @@
 #endif
   DCHECK(rinfo->rmode() < RelocInfo::NUMBER_OF_MODES);
   DCHECK(rinfo->pc() - last_pc_ >= 0);
   DCHECK(RelocInfo::LAST_STANDARD_NONCOMPACT_ENUM - RelocInfo::LAST_COMPACT_ENUM
          <= kMaxStandardNonCompactModes);
   // Use unsigned delta-encoding for pc.
   uint32_t pc_delta = static_cast<uint32_t>(rinfo->pc() - last_pc_);
   RelocInfo::Mode rmode = rinfo->rmode();
 
   // The two most common modes are given small tags, and usually fit in a byte.
-  if (rmode == RelocInfo::EMBEDDED_OBJECT) {
+  if (rmode == RelocInfo::DEOPT_REASON) {

[Michael Starzinger, 2015/02/04 11:30:51]

nit: Can we move this to after EMBEDDED_OBJECT, CODE_TARGET, and
CODE_TARGET_WITH_ID, just so that the comment talking about the "two most common
modes" is still accurate and the two most common modes really are handled first.

[loislo, 2015/02/04 14:38:50]

done

+    WriteTaggedPC(pc_delta, kLocatableTag);
+    WriteTaggedData(rinfo->data(), kDeoptReasonTag);

[Michael Starzinger, 2015/02/04 11:30:51]

Can we have a DCHECK here that the deopt reason really fits into kSmallDataBits?

[loislo, 2015/02/04 14:38:49]

done

+  } else if (rmode == RelocInfo::EMBEDDED_OBJECT) {
     WriteTaggedPC(pc_delta, kEmbeddedObjectTag);
   } else if (rmode == RelocInfo::CODE_TARGET) {
     WriteTaggedPC(pc_delta, kCodeTargetTag);
     DCHECK(begin_pos - pos_ <= RelocInfo::kMaxCallSize);
   } else if (rmode == RelocInfo::CODE_TARGET_WITH_ID) {
     // Use signed delta-encoding for id.
     DCHECK(static_cast<int>(rinfo->data()) == rinfo->data());
     int id_delta = static_cast<int>(rinfo->data()) - last_id_;
     // Check if delta is small enough to fit in a tagged byte.
     if (is_intn(id_delta, kSmallDataBits)) {
@@ skipping 139 matching lines @@
 
 
 inline void RelocIterator::ReadTaggedPosition() {
   int8_t signed_b = *pos_;
   // Signed right shift is arithmetic shift.  Tested in test-utils.cc.
   last_position_ += signed_b >> kLocatableTypeTagBits;
   rinfo_.data_ = last_position_;
 }
 
 
+inline void RelocIterator::ReadTaggedData() {
+  uint8_t unsigned_b = *pos_;
+  rinfo_.data_ = unsigned_b >> kTagBits;
+}
+
+
 static inline RelocInfo::Mode GetPositionModeFromTag(int tag) {
   DCHECK(tag == kNonstatementPositionTag ||
          tag == kStatementPositionTag);
   return (tag == kNonstatementPositionTag) ?
          RelocInfo::POSITION :
          RelocInfo::STATEMENT_POSITION;
 }
 
 
 void RelocIterator::next() {
@@ skipping 13 matching lines @@
       if (SetMode(RelocInfo::CODE_TARGET)) return;
     } else if (tag == kLocatableTag) {
       ReadTaggedPC();
       Advance();
       int locatable_tag = GetLocatableTypeTag();
       if (locatable_tag == kCodeWithIdTag) {
         if (SetMode(RelocInfo::CODE_TARGET_WITH_ID)) {
           ReadTaggedId();
           return;
         }
+      } else if (locatable_tag == kDeoptReasonTag) {
+        ReadTaggedData();
+        if (SetMode(RelocInfo::DEOPT_REASON)) return;
       } else {
-        // Compact encoding is never used for comments,
-        // so it must be a position.
         DCHECK(locatable_tag == kNonstatementPositionTag ||
                locatable_tag == kStatementPositionTag);
         if (mode_mask_ & RelocInfo::kPositionMask) {
           ReadTaggedPosition();
           if (SetMode(GetPositionModeFromTag(locatable_tag))) return;
         }
       }
     } else {
       DCHECK(tag == kDefaultTag);
       int extra_tag = GetExtraTag();
@@ skipping 144 matching lines @@
     case RelocInfo::COMMENT:
       return "comment";
     case RelocInfo::POSITION:
       return "position";
     case RelocInfo::STATEMENT_POSITION:
       return "statement position";
     case RelocInfo::EXTERNAL_REFERENCE:
       return "external reference";
     case RelocInfo::INTERNAL_REFERENCE:
       return "internal reference";
+    case RelocInfo::DEOPT_REASON:
+      return "deopt reason";
     case RelocInfo::CONST_POOL:
       return "constant pool";
     case RelocInfo::VENEER_POOL:
       return "veneer pool";
     case RelocInfo::DEBUG_BREAK_SLOT:
       return "debug break slot";
     case RelocInfo::CODE_AGE_SEQUENCE:
       return "code_age_sequence";
     case RelocInfo::NUMBER_OF_MODES:
       UNREACHABLE();
       return "number_of_modes";
   }
   return "unknown relocation type";
 }
 
 
 void RelocInfo::Print(Isolate* isolate, std::ostream& os) {  // NOLINT
   os << static_cast<const void*>(pc_) << "  " << RelocModeName(rmode_);
   if (IsComment(rmode_)) {
     os << "  (" << reinterpret_cast<char*>(data_) << ")";
+  } else if (rmode_ == DEOPT_REASON) {
+    os << "  (" << Deoptimizer::GetDeoptReason(
+                       static_cast<Deoptimizer::DeoptReason>(data_)) << ")";
   } else if (rmode_ == EMBEDDED_OBJECT) {
     os << "  (" << Brief(target_object()) << ")";
   } else if (rmode_ == EXTERNAL_REFERENCE) {
     ExternalReferenceEncoder ref_encoder(isolate);
     os << " (" << ref_encoder.NameOfAddress(target_reference()) << ")  ("
        << static_cast<const void*>(target_reference()) << ")";
   } else if (IsCodeTarget(rmode_)) {
     Code* code = Code::GetCodeFromTargetAddress(target_address());
     os << " (" << Code::Kind2String(code->kind()) << ")  ("
        << static_cast<const void*>(target_address()) << ")";
@@ skipping 40 matching lines @@
       CHECK(code->address() == HeapObject::cast(found)->address());
       break;
     }
     case RUNTIME_ENTRY:
     case JS_RETURN:
     case COMMENT:
     case POSITION:
     case STATEMENT_POSITION:
     case EXTERNAL_REFERENCE:
     case INTERNAL_REFERENCE:
+    case DEOPT_REASON:
     case CONST_POOL:
     case VENEER_POOL:
     case DEBUG_BREAK_SLOT:
     case NONE32:
     case NONE64:
       break;
     case NUMBER_OF_MODES:
       UNREACHABLE();
       break;
     case CODE_AGE_SEQUENCE:
@@ skipping 715 matching lines @@
     assembler_->RecordRelocInfo(RelocInfo::POSITION, state_.current_position);
     state_.written_position = state_.current_position;
     written = true;
   }
 
   // Return whether something was written.
   return written;
 }
 
 } }  // namespace v8::internal