DWARFAcceleratorTable: Add an iterator-based api for accessing names in the index

Summary:
Back when we were introducing the DWARF v5 name index, there was a
short discussion whether we shouldn't have a nicer api for iterating
over the index. At that time, I did not find it necessary since the
iteration over names was done only from within the index itself (and I
figured the internal implementation can deal with a slightly rough
interface).

However, now I ran into a use for this kind of API in LLDB (for finding
all names matching a regular expression), so it looked like a nice
opportunity to introduce one. To make the API more useful, I've made the
NameTableEntry class a bit smarter: it now stores the string section
reference (so it can return its name) and its position in the name index
(mainly useful for dumping/logging).

I also convert the internal users to use the new API, which also gives
test coverage for the added code.

Reviewers: JDevlieghere, aprantl, dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D47590

llvm-svn: 333738

2 files changed, 34 insertions, 37 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp b/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
index 852536b8b11..c2ba9e6027b 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
@@ -635,7 +635,7 @@ DWARFDebugNames::NameIndex::getNameTableEntry(uint32_t Index) const {
   uint32_t StringOffset = AS.getRelocatedValue(4, &StringOffsetOffset);
   uint32_t EntryOffset = AS.getU32(&EntryOffsetOffset);
   EntryOffset += EntriesBase;
-  return {StringOffset, EntryOffset};
+  return {Section.StringSection, Index, StringOffset, EntryOffset};
 }
 
 uint32_t
@@ -670,19 +670,18 @@ bool DWARFDebugNames::NameIndex::dumpEntry(ScopedPrinter &W,
   return true;
 }
 
-void DWARFDebugNames::NameIndex::dumpName(ScopedPrinter &W, uint32_t Index,
+void DWARFDebugNames::NameIndex::dumpName(ScopedPrinter &W,
+                                          const NameTableEntry &NTE,
                                           Optional<uint32_t> Hash) const {
-  const DataExtractor &SS = Section.StringSection;
-  NameTableEntry NTE = getNameTableEntry(Index);
-
-  DictScope NameScope(W, ("Name " + Twine(Index)).str());
+  DictScope NameScope(W, ("Name " + Twine(NTE.getIndex())).str());
   if (Hash)
     W.printHex("Hash", *Hash);
 
-  W.startLine() << format("String: 0x%08x", NTE.StringOffset);
-  W.getOStream() << " \"" << SS.getCStr(&NTE.StringOffset) << "\"\n";
+  W.startLine() << format("String: 0x%08x", NTE.getStringOffset());
+  W.getOStream() << " \"" << NTE.getString() << "\"\n";
 
-  while (dumpEntry(W, &NTE.EntryOffset))
+  uint32_t EntryOffset = NTE.getEntryOffset();
+  while (dumpEntry(W, &EntryOffset))
     /*empty*/;
 }
 
@@ -736,7 +735,7 @@ void DWARFDebugNames::NameIndex::dumpBucket(ScopedPrinter &W,
     if (Hash % Hdr.BucketCount != Bucket)
       break;
 
-    dumpName(W, Index, Hash);
+    dumpName(W, getNameTableEntry(Index), Hash);
   }
 }
 
@@ -755,8 +754,8 @@ LLVM_DUMP_METHOD void DWARFDebugNames::NameIndex::dump(ScopedPrinter &W) const {
   }
 
   W.startLine() << "Hash table not present\n";
-  for (uint32_t Index = 1; Index <= Hdr.NameCount; ++Index)
-    dumpName(W, Index, None);
+  for (NameTableEntry NTE : *this)
+    dumpName(W, NTE, None);
 }
 
 llvm::Error DWARFDebugNames::extract() {
@@ -787,10 +786,9 @@ DWARFDebugNames::ValueIterator::findEntryOffsetInCurrentIndex() {
   const Header &Hdr = CurrentIndex->Hdr;
   if (Hdr.BucketCount == 0) {
     // No Hash Table, We need to search through all names in the Name Index.
-    for (uint32_t Index = 1; Index <= Hdr.NameCount; ++Index) {
-      NameTableEntry NTE = CurrentIndex->getNameTableEntry(Index);
-      if (CurrentIndex->Section.StringSection.getCStr(&NTE.StringOffset) == Key)
-        return NTE.EntryOffset;
+    for (NameTableEntry NTE : *CurrentIndex) {
+      if (NTE.getString() == Key)
+        return NTE.getEntryOffset();
     }
     return None;
   }
@@ -810,8 +808,8 @@ DWARFDebugNames::ValueIterator::findEntryOffsetInCurrentIndex() {
       return None; // End of bucket
 
     NameTableEntry NTE = CurrentIndex->getNameTableEntry(Index);
-    if (CurrentIndex->Section.StringSection.getCStr(&NTE.StringOffset) == Key)
-      return NTE.EntryOffset;
+    if (NTE.getString() == Key)
+      return NTE.getEntryOffset();
   }
   return None;
 }
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp b/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp
index 67da9ccaefd..fe44071d9a2 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp
@@ -920,8 +920,7 @@ DWARFVerifier::verifyNameIndexBuckets(const DWARFDebugNames::NameIndex &NI,
       if (Hash % NI.getBucketCount() != B.Bucket)
         break;
 
-      auto NTE = NI.getNameTableEntry(Idx);
-      const char *Str = StrData.getCStr(&NTE.StringOffset);
+      const char *Str = NI.getNameTableEntry(Idx).getString();
       if (caseFoldingDjbHash(Str) != Hash) {
         error() << formatv("Name Index @ {0:x}: String ({1}) at index {2} "
                            "hashes to {3:x}, but "
@@ -1057,30 +1056,29 @@ static SmallVector<StringRef, 2> getNames(const DWARFDie &DIE) {
   return Result;
 }
 
-unsigned
-DWARFVerifier::verifyNameIndexEntries(const DWARFDebugNames::NameIndex &NI,
-                                      uint32_t Name,
-                                      const DataExtractor &StrData) {
+unsigned DWARFVerifier::verifyNameIndexEntries(
+    const DWARFDebugNames::NameIndex &NI,
+    const DWARFDebugNames::NameTableEntry &NTE) {
   // Verifying type unit indexes not supported.
   if (NI.getLocalTUCount() + NI.getForeignTUCount() > 0)
     return 0;
 
-  DWARFDebugNames::NameTableEntry NTE = NI.getNameTableEntry(Name);
-  const char *CStr = StrData.getCStr(&NTE.StringOffset);
+  const char *CStr = NTE.getString();
   if (!CStr) {
     error() << formatv(
         "Name Index @ {0:x}: Unable to get string associated with name {1}.\n",
-        NI.getUnitOffset(), Name);
+        NI.getUnitOffset(), NTE.getIndex());
     return 1;
   }
   StringRef Str(CStr);
 
   unsigned NumErrors = 0;
   unsigned NumEntries = 0;
-  uint32_t EntryID = NTE.EntryOffset;
-  Expected<DWARFDebugNames::Entry> EntryOr = NI.getEntry(&NTE.EntryOffset);
-  for (; EntryOr; ++NumEntries, EntryID = NTE.EntryOffset,
-                                EntryOr = NI.getEntry(&NTE.EntryOffset)) {
+  uint32_t EntryID = NTE.getEntryOffset();
+  uint32_t NextEntryID = EntryID;
+  Expected<DWARFDebugNames::Entry> EntryOr = NI.getEntry(&NextEntryID);
+  for (; EntryOr; ++NumEntries, EntryID = NextEntryID,
+                                EntryOr = NI.getEntry(&NextEntryID)) {
     uint32_t CUIndex = *EntryOr->getCUIndex();
     if (CUIndex > NI.getCUCount()) {
       error() << formatv("Name Index @ {0:x}: Entry @ {1:x} contains an "
@@ -1129,13 +1127,14 @@ DWARFVerifier::verifyNameIndexEntries(const DWARFDebugNames::NameIndex &NI,
                       return;
                     error() << formatv("Name Index @ {0:x}: Name {1} ({2}) is "
                                        "not associated with any entries.\n",
-                                       NI.getUnitOffset(), Name, Str);
+                                       NI.getUnitOffset(), NTE.getIndex(), Str);
                     ++NumErrors;
                   },
                   [&](const ErrorInfoBase &Info) {
-                    error() << formatv(
-                        "Name Index @ {0:x}: Name {1} ({2}): {3}\n",
-                        NI.getUnitOffset(), Name, Str, Info.message());
+                    error()
+                        << formatv("Name Index @ {0:x}: Name {1} ({2}): {3}\n",
+                                   NI.getUnitOffset(), NTE.getIndex(), Str,
+                                   Info.message());
                     ++NumErrors;
                   });
   return NumErrors;
@@ -1302,8 +1301,8 @@ unsigned DWARFVerifier::verifyDebugNames(const DWARFSection &AccelSection,
   if (NumErrors > 0)
     return NumErrors;
   for (const auto &NI : AccelTable)
-    for (uint64_t Name = 1; Name <= NI.getNameCount(); ++Name)
-      NumErrors += verifyNameIndexEntries(NI, Name, StrData);
+    for (DWARFDebugNames::NameTableEntry NTE : NI)
+      NumErrors += verifyNameIndexEntries(NI, NTE);
 
   if (NumErrors > 0)
     return NumErrors;