DWARFDebugLoc(v4): Add an incremental parsing function

Summary:
This adds a visitLocationList function to the DWARF v4 location lists,
similar to what already exists for DWARF v5. It follows the approach
outlined in previous patches (D69672), where the parsed form is always
stored in the DWARF v5 format, which makes it easier for generic code to
be built on top of that. v4 location lists are "upgraded" during
parsing, and then this upgrade is undone while dumping.

Both "inline" and section-based dumping is rewritten to reuse the
existing "generic" location list dumper. This means that the output
format is consistent for all location lists (the only thing one needs to
implement is the function which prints the "raw" form of a location
list), and that debug_loc dumping correctly processes base address
selection entries, etc.

The previous existing debug_loc functionality (e.g.,
parseOneLocationList) is rewritten on top of the new API, but it is not
removed as there is still code which uses them. This will be done in
follow-up patches, after I build the API to access the "interpreted"
location lists in a generic way (as that is what those users really
want).

Reviewers: dblaikie, probinson, JDevlieghere, aprantl, SouraVX

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69847

1 files changed, 11 insertions, 4 deletions

diff --git a/llvm/tools/llvm-dwarfdump/Statistics.cpp b/llvm/tools/llvm-dwarfdump/Statistics.cpp
index c29ad783a9e..8b92aab194d 100644
--- a/llvm/tools/llvm-dwarfdump/Statistics.cpp
+++ b/llvm/tools/llvm-dwarfdump/Statistics.cpp
@@ -249,15 +249,22 @@ static void collectStatsForDie(DWARFDie Die, uint64_t UnitLowPC, std::string FnP
       // Get PC coverage.
       if (auto DebugLocOffset = FormValue->getAsSectionOffset()) {
         auto *DebugLoc = Die.getDwarfUnit()->getContext().getDebugLoc();
+        // TODO: This code does not handle DWARF5 nor DWARF4 base address
+        // selection entries. This should use a higher-level API which abstracts
+        // these away.
         if (auto List = DebugLoc->getLocationListAtOffset(*DebugLocOffset)) {
-          for (auto Entry : List->Entries) {
-            uint64_t BytesEntryCovered = Entry.End - Entry.Begin;
+          ArrayRef<DWARFLocationEntry> Entries = List->Entries;
+          // Ignore end-of-list entries
+          Entries = Entries.drop_back();
+
+          for (auto Entry : Entries) {
+            uint64_t BytesEntryCovered = Entry.Value1 - Entry.Value0;
             BytesCovered += BytesEntryCovered;
             if (IsEntryValue(Entry.Loc))
               BytesEntryValuesCovered += BytesEntryCovered;
           }
-          if (List->Entries.size()) {
-            uint64_t FirstDef = List->Entries[0].Begin;
+          if (Entries.size()) {
+            uint64_t FirstDef = Entries[0].Value0;
             uint64_t UnitOfs = UnitLowPC; 
             // Ranges sometimes start before the lexical scope.
             if (UnitOfs + FirstDef >= ScopeLowPC)