Record AST ids in relocation info at spots where we collect dynamic type feedback.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index ca30e19cb4d2d1544cb2d1778a80af7d1e997e14..662f1b85d5e94579ff2134f9c6a50716b7f514cb 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -30,7 +30,7 @@
 
 // The original source code covered by the above license above has been
 // modified significantly by Google Inc.
-// Copyright 2006-2009 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 
 #include "v8.h"
 
@@ -96,46 +96,60 @@ int Label::pos() const {
 // The encoding relies on the fact that there are less than 14
 // different relocation modes.
 //

[Vitaly Repeshko, 2011/04/15 01:24:43]

It'd be nice to describe the tag structure, i.e. the two least significant bits
are "tag", the next four bits are "extra tag", and finally the two most
significant bits are "top tag".

[William Hesse, 2011/04/15 11:51:27]

I have a rewrite of this, that I forgot to copy in.  Here it is.

-// embedded_object:    [6 bits pc delta] 00
+// Written by WriteTaggedPC:
+//     embedded_object:      [6 bits pc delta] 00
 //
-// code_taget:         [6 bits pc delta] 01
+//     code_target:          [6 bits pc delta] 01
 //
-// position:           [6 bits pc delta] 10,
-//                     [7 bits signed data delta] 0
+// Written by WriteTaggedPC, WriteTaggedData sequence:
+//     code_target_with_id:  [6 bits pc delta] 10,
+//                           [6 bits signed data delta] 00
 //
-// statement_position: [6 bits pc delta] 10,
-//                     [7 bits signed data delta] 1
+//     position:             [6 bits pc delta] 10,
+//                           [6 bits signed data delta] 01
 //
-// any nondata mode:   00 [4 bits rmode] 11,  // rmode: 0..13 only
-//                     00 [6 bits pc delta]
+//     statement_position:   [6 bits pc delta] 10,
+//                           [6 bits signed data delta] 10
 //
-// pc-jump:            00 1111 11,
-//                     00 [6 bits pc delta]
+// Written by WriteExtraTag:
+//     any nondata mode:     00 [4 bit rmode_field] 11,
+//                           00 [6 bits pc delta]
+//         (The rmode_field encodes rmode - RelocInfo::LAST_COMPACT_ENUM,
+//          and is between 0000 and 1101)
 //
-// pc-jump:            01 1111 11,
-// (variable length)   7 - 26 bit pc delta, written in chunks of 7
-//                     bits, the lowest 7 bits written first.
+//     pc-jump:              00 1111 11,
+//                           00 [6 bits pc delta]
 //
-// data-jump + pos:    00 1110 11,
-//                     signed intptr_t, lowest byte written first
+// Written by WriteVariableLengthPCJump, implicitly called by WriteTaggedPC.
+//     pc-jump (variable length):
+//                           01 1111 11,
+//                           [7 bits data] 0
+//                                ...
+//                           [7 bits data] 1
+//             (Bits 6..31 of pc delta, with leading zeroes
+//              dropped, and last non-zero chunk tagged with 1.)
 //
-// data-jump + st.pos: 01 1110 11,
-//                     signed intptr_t, lowest byte written first
+// data-jump + position :    00 1110 11,

[Vitaly Repeshko, 2011/04/15 01:24:43]

We need a similar "Written by" comment here.

+//                           signed intptr_t, lowest byte written first
 //
-// data-jump + comm.:  10 1110 11,
-//                     signed intptr_t, lowest byte written first
+// data-jump + statement position:
+//                           01 1110 11,
+//                           signed intptr_t, lowest byte written first
+//
+// data-jump + comment:      10 1110 11,
+//                           signed intptr_t, lowest byte written first
 //
 const int kMaxRelocModes = 14;
 
 const int kTagBits = 2;
 const int kTagMask = (1 << kTagBits) - 1;
 const int kExtraTagBits = 4;
-const int kPositionTypeTagBits = 1;
-const int kSmallDataBits = kBitsPerByte - kPositionTypeTagBits;
+const int kLocatableTypeTagBits = 2;
+const int kSmallDataBits = kBitsPerByte - kLocatableTypeTagBits;
 
 const int kEmbeddedObjectTag = 0;
 const int kCodeTargetTag = 1;
-const int kPositionTag = 2;
+const int kLocatableTag = 2;
 const int kDefaultTag = 3;
 
 const int kPCJumpTag = (1 << kExtraTagBits) - 1;

[Vitaly Repeshko, 2011/04/15 01:24:43]

Let's rename this to kPCJumpExtraTag.

[William Hesse, 2011/04/15 11:51:27]

Done.

@@ -154,9 +168,10 @@ const int kLastChunkTag = 1;
 
 const int kDataJumpTag = kPCJumpTag - 1;

[Vitaly Repeshko, 2011/04/15 01:24:43]

kDataJumpExtraTag

[William Hesse, 2011/04/15 11:51:27]

Done.

 
-const int kNonstatementPositionTag = 0;
-const int kStatementPositionTag = 1;
-const int kCommentTag = 2;
+const int kCodeWithIdTag = 0;
+const int kNonstatementPositionTag = 1;
+const int kStatementPositionTag = 2;
+const int kCommentTag = 3;
 
 
 uint32_t RelocInfoWriter::WriteVariableLengthPCJump(uint32_t pc_delta) {
@@ -187,7 +202,7 @@ void RelocInfoWriter::WriteTaggedPC(uint32_t pc_delta, int tag) {
 
 
 void RelocInfoWriter::WriteTaggedData(intptr_t data_delta, int tag) {
-  *--pos_ = static_cast<byte>(data_delta << kPositionTypeTagBits | tag);
+  *--pos_ = static_cast<byte>(data_delta << kLocatableTypeTagBits | tag);
 }
 
 
@@ -206,11 +221,21 @@ void RelocInfoWriter::WriteExtraTaggedPC(uint32_t pc_delta, int extra_tag) {
 }
 
 
+void RelocInfoWriter::WriteExtraTaggedIntData(int data_delta, int top_tag)
+{

[Vitaly Repeshko, 2011/04/15 01:24:43]

nit: Put '{' on the previous line.

[William Hesse, 2011/04/15 11:51:27]

Done.

+  WriteExtraTag(kDataJumpTag, top_tag);
+  for (int i = 0; i < kIntSize; i++) {
+    *--pos_ = static_cast<byte>(data_delta);
+    // Signed right shift is arithmetic shift.  Tested in test-utils.cc.
+    data_delta = data_delta >> kBitsPerByte;
+  }
+}
+
 void RelocInfoWriter::WriteExtraTaggedData(intptr_t data_delta, int top_tag) {
   WriteExtraTag(kDataJumpTag, top_tag);
   for (int i = 0; i < kIntptrSize; i++) {
     *--pos_ = static_cast<byte>(data_delta);
-  // Signed right shift is arithmetic shift.  Tested in test-utils.cc.
+    // Signed right shift is arithmetic shift.  Tested in test-utils.cc.
     data_delta = data_delta >> kBitsPerByte;
   }
 }
@@ -221,7 +246,8 @@ void RelocInfoWriter::Write(const RelocInfo* rinfo) {
   byte* begin_pos = pos_;
 #endif
   ASSERT(rinfo->pc() - last_pc_ >= 0);
-  ASSERT(RelocInfo::NUMBER_OF_MODES <= kMaxRelocModes);
+  ASSERT(RelocInfo::NUMBER_OF_MODES - RelocInfo::LAST_CODE_ENUM <=

[Vitaly Repeshko, 2011/04/15 01:24:43]

LAST_COMPACT_ENUM?

[William Hesse, 2011/04/15 11:51:27]

Done.

+         kMaxRelocModes);
   // Use unsigned delta-encoding for pc.
   uint32_t pc_delta = static_cast<uint32_t>(rinfo->pc() - last_pc_);
   RelocInfo::Mode rmode = rinfo->rmode();
@@ -232,35 +258,48 @@ void RelocInfoWriter::Write(const RelocInfo* rinfo) {
   } else if (rmode == RelocInfo::CODE_TARGET) {
     WriteTaggedPC(pc_delta, kCodeTargetTag);
     ASSERT(begin_pos - pos_ <= RelocInfo::kMaxCallSize);
+  } else if (rmode == RelocInfo::CODE_TARGET_WITH_ID) {
+    // Use signed delta-encoding for id.
+    ASSERT(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)) {
+      WriteTaggedPC(pc_delta, kLocatableTag);
+      WriteTaggedData(id_delta, kCodeWithIdTag);
+    } else {
+      // Otherwise, use costly encoding.
+      WriteExtraTaggedPC(pc_delta, kPCJumpTag);
+      WriteExtraTaggedIntData(id_delta, kCodeWithIdTag);
+    }
+    last_id_ = static_cast<int>(rinfo->data());
   } else if (RelocInfo::IsPosition(rmode)) {
-    // Use signed delta-encoding for data.
-    intptr_t data_delta = rinfo->data() - last_data_;
-    int pos_type_tag = rmode == RelocInfo::POSITION ? kNonstatementPositionTag
-                                                    : kStatementPositionTag;
-    // Check if data is small enough to fit in a tagged byte.
-    // We cannot use is_intn because data_delta is not an int32_t.
-    if (data_delta >= -(1 << (kSmallDataBits-1)) &&
-        data_delta < 1 << (kSmallDataBits-1)) {
-      WriteTaggedPC(pc_delta, kPositionTag);
-      WriteTaggedData(data_delta, pos_type_tag);
-      last_data_ = rinfo->data();
+    // Use signed delta-encoding for position.
+    ASSERT(static_cast<int>(rinfo->data()) == rinfo->data());
+    int pos_delta = static_cast<int>(rinfo->data()) - last_position_;
+    int pos_type_tag = (rmode == RelocInfo::POSITION) ? kNonstatementPositionTag
+                                                      : kStatementPositionTag;
+    // Check if delta is small enough to fit in a tagged byte.
+    if (is_intn(pos_delta, kSmallDataBits)) {
+      WriteTaggedPC(pc_delta, kLocatableTag);
+      WriteTaggedData(pos_delta, pos_type_tag);
     } else {
       // Otherwise, use costly encoding.
       WriteExtraTaggedPC(pc_delta, kPCJumpTag);
-      WriteExtraTaggedData(data_delta, pos_type_tag);
-      last_data_ = rinfo->data();
+      WriteExtraTaggedIntData(pos_delta, pos_type_tag);
     }
+    last_position_ = static_cast<int>(rinfo->data());
   } else if (RelocInfo::IsComment(rmode)) {
     // Comments are normally not generated, so we use the costly encoding.
     WriteExtraTaggedPC(pc_delta, kPCJumpTag);
-    WriteExtraTaggedData(rinfo->data() - last_data_, kCommentTag);
-    last_data_ = rinfo->data();
+    WriteExtraTaggedData(rinfo->data(), kCommentTag);
     ASSERT(begin_pos - pos_ >= RelocInfo::kMinRelocCommentSize);
   } else {
+    ASSERT(rmode > RelocInfo::LAST_COMPACT_ENUM);
+    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.
-    ASSERT(rmode < kPCJumpTag && rmode < kDataJumpTag);
-    WriteExtraTaggedPC(pc_delta, rmode);
+    ASSERT(saved_mode < kPCJumpTag && saved_mode < kDataJumpTag);
+    WriteExtraTaggedPC(pc_delta, saved_mode);
   }
   last_pc_ = rinfo->pc();
 #ifdef DEBUG
@@ -294,12 +333,32 @@ inline void RelocIterator::AdvanceReadPC() {
 }
 
 
+void RelocIterator::AdvanceReadId() {
+  int x = 0;
+  for (int i = 0; i < kIntSize; i++) {
+    x |= static_cast<int>(*--pos_) << i * kBitsPerByte;
+  }
+  last_id_ += x;
+  rinfo_.data_ = last_id_;
+}
+
+
+void RelocIterator::AdvanceReadPosition() {
+  int x = 0;
+  for (int i = 0; i < kIntSize; i++) {
+    x |= static_cast<int>(*--pos_) << i * kBitsPerByte;
+  }
+  last_position_ += x;
+  rinfo_.data_ = last_position_;
+}
+
+
 void RelocIterator::AdvanceReadData() {
   intptr_t x = 0;
   for (int i = 0; i < kIntptrSize; i++) {
     x |= static_cast<intptr_t>(*--pos_) << i * kBitsPerByte;
   }
-  rinfo_.data_ += x;
+  rinfo_.data_ = x;
 }
 
 
@@ -319,27 +378,33 @@ void RelocIterator::AdvanceReadVariableLengthPCJump() {
 }
 
 
-inline int RelocIterator::GetPositionTypeTag() {
-  return *pos_ & ((1 << kPositionTypeTagBits) - 1);
+inline int RelocIterator::GetLocatableTypeTag() {
+  return *pos_ & ((1 << kLocatableTypeTagBits) - 1);
 }
 
 
-inline void RelocIterator::ReadTaggedData() {
+inline void RelocIterator::ReadTaggedId() {
   int8_t signed_b = *pos_;
   // Signed right shift is arithmetic shift.  Tested in test-utils.cc.
-  rinfo_.data_ += signed_b >> kPositionTypeTagBits;
+  last_id_ += signed_b >> kLocatableTypeTagBits;
+  rinfo_.data_ = last_id_;
 }
 
 
-inline RelocInfo::Mode RelocIterator::DebugInfoModeFromTag(int tag) {
-  if (tag == kStatementPositionTag) {
-    return RelocInfo::STATEMENT_POSITION;
-  } else if (tag == kNonstatementPositionTag) {
-    return RelocInfo::POSITION;
-  } else {
-    ASSERT(tag == kCommentTag);
-    return RelocInfo::COMMENT;
-  }
+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_;
+}
+
+
+static inline RelocInfo::Mode GetPositionModeFromTag(int tag) {
+  ASSERT(tag == kNonstatementPositionTag ||
+         tag == kStatementPositionTag);
+  return (tag == kNonstatementPositionTag) ?
+         RelocInfo::POSITION :
+         RelocInfo::STATEMENT_POSITION;
 }
 
 
@@ -358,13 +423,24 @@ void RelocIterator::next() {
     } else if (tag == kCodeTargetTag) {
       ReadTaggedPC();
       if (SetMode(RelocInfo::CODE_TARGET)) return;
-    } else if (tag == kPositionTag) {
+    } else if (tag == kLocatableTag) {
       ReadTaggedPC();
       Advance();
-      // Check if we want source positions.
-      if (mode_mask_ & RelocInfo::kPositionMask) {
-        ReadTaggedData();
-        if (SetMode(DebugInfoModeFromTag(GetPositionTypeTag()))) return;
+      int locatable_tag = GetLocatableTypeTag();
+      if (locatable_tag == kCodeWithIdTag) {
+        if (SetMode(RelocInfo::CODE_TARGET_WITH_ID)) {
+          ReadTaggedId();
+          return;
+        }
+      } else {
+        // Compact encoding is never used for comments,
+        // so it must be a position.
+        ASSERT(locatable_tag == kNonstatementPositionTag ||
+               locatable_tag == kStatementPositionTag);
+        if (mode_mask_ & RelocInfo::kPositionMask) {
+          ReadTaggedPosition();
+          if (SetMode(GetPositionModeFromTag(locatable_tag))) return;
+        }
       }
     } else {
       ASSERT(tag == kDefaultTag);
@@ -377,18 +453,34 @@ void RelocIterator::next() {
           AdvanceReadPC();
         }
       } else if (extra_tag == kDataJumpTag) {
-        // Check if we want debug modes (the only ones with data).
-        if (mode_mask_ & RelocInfo::kDebugMask) {
-          int top_tag = GetTopTag();
-          AdvanceReadData();
-          if (SetMode(DebugInfoModeFromTag(top_tag))) return;
+        int locatable_tag = GetTopTag();
+        if (locatable_tag == kCodeWithIdTag) {
+          if (SetMode(RelocInfo::CODE_TARGET_WITH_ID)) {
+            AdvanceReadId();
+            return;
+          }
+          Advance(kIntSize);
+        } else if (locatable_tag != kCommentTag) {
+          ASSERT(locatable_tag == kNonstatementPositionTag ||
+                 locatable_tag == kStatementPositionTag);
+          if (mode_mask_ & RelocInfo::kPositionMask) {
+            AdvanceReadPosition();
+            if (SetMode(GetPositionModeFromTag(locatable_tag))) return;
+          } else {
+            Advance(kIntSize);
+          }
         } else {
-          // Otherwise, just skip over the data.
+          ASSERT(locatable_tag == kCommentTag);
+          if (SetMode(RelocInfo::COMMENT)) {
+            AdvanceReadData();
+            return;
+          }
           Advance(kIntptrSize);
         }
       } else {
         AdvanceReadPC();
-        if (SetMode(static_cast<RelocInfo::Mode>(extra_tag))) return;
+        int rmode = extra_tag + RelocInfo::LAST_COMPACT_ENUM;
+        if (SetMode(static_cast<RelocInfo::Mode>(rmode))) return;
       }
     }
   }
@@ -404,6 +496,8 @@ RelocIterator::RelocIterator(Code* code, int mode_mask) {
   end_ = code->relocation_start();
   done_ = false;
   mode_mask_ = mode_mask;
+  last_id_ = 0;
+  last_position_ = 0;
   if (mode_mask_ == 0) pos_ = end_;
   next();
 }
@@ -417,6 +511,8 @@ RelocIterator::RelocIterator(const CodeDesc& desc, int mode_mask) {
   end_ = pos_ - desc.reloc_size;
   done_ = false;
   mode_mask_ = mode_mask;
+  last_id_ = 0;
+  last_position_ = 0;
   if (mode_mask_ == 0) pos_ = end_;
   next();
 }
@@ -444,6 +540,8 @@ const char* RelocInfo::RelocModeName(RelocInfo::Mode rmode) {
       return "debug break";
     case RelocInfo::CODE_TARGET:
       return "code target";
+    case RelocInfo::CODE_TARGET_WITH_ID:
+      return "code target with id";
     case RelocInfo::GLOBAL_PROPERTY_CELL:
       return "global property cell";
     case RelocInfo::RUNTIME_ENTRY:
@@ -490,6 +588,9 @@ void RelocInfo::Print(FILE* out) {
     Code* code = Code::GetCodeFromTargetAddress(target_address());
     PrintF(out, " (%s)  (%p)", Code::Kind2String(code->kind()),
            target_address());
+    if (rmode_ == CODE_TARGET_WITH_ID) {
+      PrintF(" (id=%d)", static_cast<int>(data_));
+    }
   } else if (IsPosition(rmode_)) {
     PrintF(out, "  (%" V8_PTR_PREFIX "d)", data());
   } else if (rmode_ == RelocInfo::RUNTIME_ENTRY &&
@@ -523,6 +624,7 @@ void RelocInfo::Verify() {
 #endif
     case CONSTRUCT_CALL:
     case CODE_TARGET_CONTEXT:
+    case CODE_TARGET_WITH_ID:
     case CODE_TARGET: {
       // convert inline target address to code object
       Address addr = target_address();