DebugInfo: Don't use implicit zero addr_base

(found when LLVM fails to emit addr_base for gmlt+DWARFv5)

Author: dwblaikie

llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h

@@ -210,7 +210,7 @@ class DWARFUnit {
   StringRef StringSection;
   const DWARFSection &StringOffsetSection;
   const DWARFSection *AddrOffsetSection;
-  uint32_t AddrOffsetSectionBase = 0;
+  Optional<uint64_t> AddrOffsetSectionBase;
   bool isLittleEndian;
   bool IsDWO;
   const DWARFUnitVector &UnitVector;

llvm/lib/DebugInfo/DWARF/DWARFFormValue.cpp

@@ -412,7 +412,7 @@ void DWARFFormValue::dump(raw_ostream &OS, DIDumpOptions DumpOpts) const {
     if (A)
       dumpSectionedAddress(AddrOS, DumpOpts, *A);
     else
-      OS << "<no .debug_addr section>";
+      OS << "<unresolved>";
     break;
   }
   case DW_FORM_flag_present:

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

@@ -228,7 +228,9 @@ DWARFUnit::getAddrOffsetSectionItem(uint32_t Index) const {
     if (I != R.end() && std::next(I) == R.end())
       return (*I)->getAddrOffsetSectionItem(Index);
   }
-  uint64_t Offset = AddrOffsetSectionBase + Index * getAddressByteSize();
+  if (!AddrOffsetSectionBase)
+    return None;
+  uint64_t Offset = *AddrOffsetSectionBase + Index * getAddressByteSize();
   if (AddrOffsetSection->Data.size() < Offset + getAddressByteSize())
     return None;
   DWARFDataExtractor DA(Context.getDWARFObj(), *AddrOffsetSection,
@@ -360,7 +362,7 @@ void DWARFUnit::clear() {
   BaseAddr.reset();
   RangeSectionBase = 0;
   LocSectionBase = 0;
-  AddrOffsetSectionBase = 0;
+  AddrOffsetSectionBase = None;
   clearDIEs(false);
   DWO.reset();
 }
@@ -448,13 +450,13 @@ Error DWARFUnit::tryExtractDIEsIfNeeded(bool CUDieOnly) {
   if (Optional<uint64_t> DWOId = toUnsigned(UnitDie.find(DW_AT_GNU_dwo_id)))
     Header.setDWOId(*DWOId);
   if (!IsDWO) {
-    assert(AddrOffsetSectionBase == 0);
+    assert(AddrOffsetSectionBase == None);
     assert(RangeSectionBase == 0);
     assert(LocSectionBase == 0);
-    AddrOffsetSectionBase = toSectionOffset(UnitDie.find(DW_AT_addr_base), 0);
+    AddrOffsetSectionBase = toSectionOffset(UnitDie.find(DW_AT_addr_base));
     if (!AddrOffsetSectionBase)
       AddrOffsetSectionBase =
-          toSectionOffset(UnitDie.find(DW_AT_GNU_addr_base), 0);
+          toSectionOffset(UnitDie.find(DW_AT_GNU_addr_base));
     RangeSectionBase = toSectionOffset(UnitDie.find(DW_AT_rnglists_base), 0);
     LocSectionBase = toSectionOffset(UnitDie.find(DW_AT_loclists_base), 0);
   }
@@ -578,7 +580,8 @@ bool DWARFUnit::parseDWO() {
     return false;
   DWO = std::shared_ptr<DWARFCompileUnit>(std::move(DWOContext), DWOCU);
   // Share .debug_addr and .debug_ranges section with compile unit in .dwo
-  DWO->setAddrOffsetSection(AddrOffsetSection, AddrOffsetSectionBase);
+  if (AddrOffsetSectionBase)
+    DWO->setAddrOffsetSection(AddrOffsetSection, *AddrOffsetSectionBase);
   if (getVersion() >= 5) {
     DWO->setRangesSection(&Context.getDWARFObj().getRnglistsDWOSection(), 0);
     DWARFDataExtractor RangesDA(Context.getDWARFObj(), *RangeSection,

llvm/test/tools/llvm-dwarfdump/X86/debug_info_addrx.s

@@ -5,17 +5,17 @@
 # CHECK: DW_TAG_compile_unit
 # CHECK:   DW_AT_low_pc                                              (0x0000000000000000)
 # VERBOSE: DW_AT_low_pc [DW_FORM_addrx] (indexed (00000000) address = 0x0000000000000000 ".text")
-# FIXME: There is a debug_addr section, it's just that the index is outside its 
-#        bounds (both of the section, and the range defined by the header for the
-#        debug_addr contribution for this CU)
-# CHECK:   DW_AT_low_pc                 (indexed (00000001) address = <no .debug_addr section>)
-# VERBOSE: DW_AT_low_pc [DW_FORM_addrx] (indexed (00000001) address = <no .debug_addr section>)
+# FIXME: Improve the error message from "unresolved" to describe the specific
+#        issue (in this case, the index is outside the bounds of the debug_addr
+#        contribution/debug_addr section)
+# CHECK:   DW_AT_low_pc                 (indexed (00000001) address = <unresolved>)
+# VERBOSE: DW_AT_low_pc [DW_FORM_addrx] (indexed (00000001) address = <unresolved>)
 
 # CHECK: DW_TAG_compile_unit
 # FIXME: Should error "no debug_addr contribution" - rather than parsing debug_addr
 #        from the start, incorrectly interpreting the header bytes as an address.
-# CHECK:   DW_AT_low_pc                                              (0x000800050000000c)
-# VERBOSE: DW_AT_low_pc [DW_FORM_addrx] (indexed (00000000) address = 0x000800050000000c)
+# CHECK:   DW_AT_low_pc                 (indexed (00000000) address = <unresolved>)
+# VERBOSE: DW_AT_low_pc [DW_FORM_addrx] (indexed (00000000) address = <unresolved>)
 
 	.globl	foo                     # -- Begin function foo
 foo:                                    # @foo