Externalize deoptimization reasons.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index deabe3b776a9377e10f0f4d3346946ab036c10af..4c5eda198106e5c9ef9bac136788e5188dad9b84 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -256,6 +256,7 @@ int Label::pos() const {
 //   position:            01
 //   statement_position:  10
 //   comment:             11 (not used in short_data_record)
+//   deopt_reason:        11 (not used in long_data_record)
 //
 //  Long record format:
 //    4-bit middle_tag:
@@ -328,6 +329,10 @@ const int kNonstatementPositionTag = 1;
 const int kStatementPositionTag = 2;
 const int kCommentTag = 3;
 
+// Reuse the same value for deopt reason tag in short record format.
+// It is possible because we use kCommentTag only for the long record format.
+const int kDeoptReasonTag = 3;
+
 const int kPoolExtraTag = kPCJumpExtraTag - 2;
 const int kConstPoolTag = 0;
 const int kVeneerPoolTag = 1;
@@ -442,6 +447,10 @@ void RelocInfoWriter::Write(const RelocInfo* rinfo) {
       WriteExtraTaggedIntData(id_delta, kCodeWithIdTag);
     }
     last_id_ = static_cast<int>(rinfo->data());
+  } else if (rmode == RelocInfo::DEOPT_REASON) {
+    DCHECK(rinfo->data() < (1 << kSmallDataBits));
+    WriteTaggedPC(pc_delta, kLocatableTag);
+    WriteTaggedData(rinfo->data(), kDeoptReasonTag);
   } else if (RelocInfo::IsPosition(rmode)) {
     // Use signed delta-encoding for position.
     DCHECK(static_cast<int>(rinfo->data()) == rinfo->data());
@@ -473,7 +482,7 @@ void RelocInfoWriter::Write(const RelocInfo* rinfo) {
     int saved_mode = rmode - RelocInfo::LAST_COMPACT_ENUM;
     // For all other modes we simply use the mode as the extra tag.
     // None of these modes need a data component.
-    DCHECK(saved_mode < kPCJumpExtraTag && saved_mode < kDataJumpExtraTag);
+    DCHECK(saved_mode < kPoolExtraTag);
     WriteExtraTaggedPC(pc_delta, saved_mode);
   }
   last_pc_ = rinfo->pc();
@@ -583,6 +592,12 @@ inline void RelocIterator::ReadTaggedPosition() {
 }
 
 
+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);
@@ -616,9 +631,10 @@ void RelocIterator::next() {
           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) {
@@ -783,6 +799,8 @@ const char* RelocInfo::RelocModeName(RelocInfo::Mode rmode) {
       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:
@@ -803,6 +821,9 @@ 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) {
@@ -863,6 +884,7 @@ void RelocInfo::Verify(Isolate* isolate) {
     case STATEMENT_POSITION:
     case EXTERNAL_REFERENCE:
     case INTERNAL_REFERENCE:
+    case DEOPT_REASON:
     case CONST_POOL:
     case VENEER_POOL:
     case DEBUG_BREAK_SLOT: