llvm-symbolizer: support DW_FORM_loclistx locations.

Summary:
With -gdwarf-5 local variable locations are emitted as DW_FORM_loclistx
form instead of the regular DW_FORM_sec_offset. Teach
DWARFDie::getLocations to understand the new format and use it in
llvm-symbolizer "FRAME" command.

Reviewers: pcc, jdoerfert

Subscribers: srhines, aprantl, hiraditya, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70756

2 files changed, 27 insertions, 31 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index b268d2e6aef..e452c7636b1 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -1077,33 +1077,6 @@ getExpressionFrameOffset(ArrayRef<uint8_t> Expr,
   return None;
 }
 
-static Optional<int64_t>
-getLocationFrameOffset(DWARFCompileUnit *CU, DWARFFormValue &FormValue,
-                       Optional<unsigned> FrameBaseReg) {
-  if (Optional<ArrayRef<uint8_t>> Location = FormValue.getAsBlock()) {
-    return getExpressionFrameOffset(*Location, FrameBaseReg);
-  } else if (FormValue.isFormClass(DWARFFormValue::FC_SectionOffset)) {
-    uint64_t Offset = *FormValue.getAsSectionOffset();
-    const DWARFLocationTable &LocTable = CU->getLocationTable();
-    Optional<int64_t> FrameOffset;
-    Error E = LocTable.visitLocationList(
-        &Offset, [&](const DWARFLocationEntry &Entry) {
-          if (Entry.Kind == dwarf::DW_LLE_base_address ||
-              Entry.Kind == dwarf::DW_LLE_base_addressx ||
-              Entry.Kind == dwarf::DW_LLE_end_of_list) {
-            return true;
-          }
-          if ((FrameOffset = getExpressionFrameOffset(Entry.Loc, FrameBaseReg)))
-            return false;
-          return true;
-        });
-    if (E)
-      return None;
-    return FrameOffset;
-  }
-  return None;
-}
-
 void DWARFContext::addLocalsForDie(DWARFCompileUnit *CU, DWARFDie Subprogram,
                                    DWARFDie Die, std::vector<DILocal> &Result) {
   if (Die.getTag() == DW_TAG_variable ||
@@ -1119,8 +1092,21 @@ void DWARFContext::addLocalsForDie(DWARFCompileUnit *CU, DWARFDie Subprogram,
             (*Expr)[0] <= DW_OP_reg31) {
           FrameBaseReg = (*Expr)[0] - DW_OP_reg0;
         }
-    if (auto LocationAttr = Die.find(DW_AT_location))
-      Local.FrameOffset = getLocationFrameOffset(CU, *LocationAttr, FrameBaseReg);
+
+    if (Expected<std::vector<DWARFLocationExpression>> Loc =
+            Die.getLocations(DW_AT_location)) {
+      for (const auto &Entry : *Loc) {
+        if (Optional<int64_t> FrameOffset =
+                getExpressionFrameOffset(Entry.Expr, FrameBaseReg)) {
+          Local.FrameOffset = *FrameOffset;
+          break;
+        }
+      }
+    } else {
+      // FIXME: missing DW_AT_location is OK here, but other errors should be
+      // reported to the user.
+      consumeError(Loc.takeError());
+    }
 
     if (auto TagOffsetAttr = Die.find(DW_AT_LLVM_tag_offset))
       Local.TagOffset = TagOffsetAttr->getAsUnsignedConstant();
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index 4b86359c04e..558d8006501 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -495,8 +495,18 @@ DWARFDie::getLocations(dwarf::Attribute Attr) const {
     return createStringError(inconvertibleErrorCode(), "No %s",
                              dwarf::AttributeString(Attr).data());
 
-  if (Optional<uint64_t> Off = Location->getAsSectionOffset())
-    return U->findLoclistFromOffset(*Off);
+  if (Optional<uint64_t> Off = Location->getAsSectionOffset()) {
+    uint64_t Offset = *Off;
+
+    if (Location->getForm() == DW_FORM_loclistx) {
+      if (auto LoclistOffset = U->getLoclistOffset(Offset))
+        Offset = *LoclistOffset;
+      else
+        return createStringError(inconvertibleErrorCode(),
+                                 "Loclist table not found");
+    }
+    return U->findLoclistFromOffset(Offset);
+  }
 
   if (Optional<ArrayRef<uint8_t>> Expr = Location->getAsBlock()) {
     return DWARFLocationExpressionsVector{