[DWARF] Make llvm-dwarfdump display location lists in a .dwp file correctly. Fixes PR38990.

[wolfgangp]

Summary

Considers the index when extracting location lists from a .dwp file. The location list sections are added when constructing units.

Majority of the patch by David Blaikie.

@dblaikie:
I've extracted the cleanup portion of your patch with the intent to apply it separately.

[dblaikie]

lib/DebugInfo/DWARF/DWARFDie.cpp

117–120

Any chance this could be done when the unit is constructed, rather than every time a loc list is dumped? (ie: could the unit either be constructed with a StringRef of the LocSection already offset to the index entry - or have the unit constructor take the whole LocSection, examine its index entry, and then store the sub-section adjusted/computed using the index entry)

lib/DebugInfo/DWARF/DWARFUnit.cpp

454

Could be worth doing this isDWO->IsDWO rename separately, easy to commit & simplify this change a bit.

[wolfgangp]

Addressed review comments:

• Keeping track of locsection data separately so we can adjust it when handling dwp files.
• removing a cleanup that can be applied later.

lib/DebugInfo/DWARF/DWARFDie.cpp

117–120

We still need a pointer or reference to the whole loc section, because there are relocations in it, so I'm keeping track of the data separately. The constructor then adjusts it if necessary.

The alternative is to use a StringRef as you say, and get the section from the context when needed. Not sure what's preferable, but using the section for construction seems slightly more consistent overall.

[dblaikie]

include/llvm/DebugInfo/DWARF/DWARFUnit.h

203

Could this be a union, perhaps?

[wolfgangp]

Made the location list section pointer and the stringref that describes its data a union rather than a pair.

include/llvm/DebugInfo/DWARF/DWARFUnit.h

203

Yes, that's better. I guess we can't use std::variant yet?

[dblaikie]

include/llvm/DebugInfo/DWARF/DWARFUnit.h

203

I don't think so, unfortunately :/

[dblaikie]

llvm/trunk/lib/DebugInfo/DWARF/DWARFUnit.cpp

183–188 ↗

(On Diff #170239)

Not sure if I mentioned this, but any chance we could generalize this solution for all contribution/unit index handling? (so unindexed sections are passed into the ctor here, but they're all converted to indexed offset sections from here on out?) For example the str_offsets section handling in extractDIEsIfNeeded could be moved up here, maybe?

include/llvm/DebugInfo/DWARF/DWARFCompileUnit.h

 #include "llvm/DebugInfo/DWARF/DWARFUnit.h"
 #include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
 
 namespace llvm {
 
 class DWARFCompileUnit : public DWARFUnit {
 public:
   DWARFCompileUnit(DWARFContext &Context, const DWARFSection &Section,
-                   const DWARFUnitHeader &Header,
-                   const DWARFDebugAbbrev *DA, const DWARFSection *RS,
+                   const DWARFUnitHeader &Header, const DWARFDebugAbbrev *DA,
+                   const DWARFSection *RS, const DWARFSection *LocSection,
                    StringRef SS, const DWARFSection &SOS,
                    const DWARFSection *AOS, const DWARFSection &LS, bool LE,
                    bool IsDWO, const DWARFUnitVector &UnitVector)
-      : DWARFUnit(Context, Section, Header, DA, RS, SS, SOS, AOS, LS, LE, IsDWO,
-                  UnitVector) {}
+      : DWARFUnit(Context, Section, Header, DA, RS, LocSection, SS, SOS, AOS,
+                  LS, LE, IsDWO, UnitVector) {}
 
   /// VTable anchor.
   ~DWARFCompileUnit() override;
   /// Dump this compile unit to \p OS.
   void dump(raw_ostream &OS, DIDumpOptions DumpOpts) override;
   /// Enable LLVM-style RTTI.
   static bool classof(const DWARFUnit *U) { return !U->isTypeUnit(); }
 };
 
 } // end namespace llvm
 
 #endif // LLVM_DEBUGINFO_DWARFCOMPILEUNIT_H

include/llvm/DebugInfo/DWARF/DWARFTypeUnit.h

 class DWARFContext;
 class DWARFDebugAbbrev;
 struct DWARFSection;
 class raw_ostream;
 
 class DWARFTypeUnit : public DWARFUnit {
 public:
   DWARFTypeUnit(DWARFContext &Context, const DWARFSection &Section,
-                const DWARFUnitHeader &Header,
-                const DWARFDebugAbbrev *DA, const DWARFSection *RS,
+                const DWARFUnitHeader &Header, const DWARFDebugAbbrev *DA,
+                const DWARFSection *RS, const DWARFSection *LocSection,
                 StringRef SS, const DWARFSection &SOS, const DWARFSection *AOS,
                 const DWARFSection &LS, bool LE, bool IsDWO,
                 const DWARFUnitVector &UnitVector)
-      : DWARFUnit(Context, Section, Header, DA, RS, SS, SOS, AOS, LS, LE, IsDWO,
-                  UnitVector) {}
+      : DWARFUnit(Context, Section, Header, DA, RS, LocSection, SS, SOS, AOS,
+                  LS, LE, IsDWO, UnitVector) {}
 
   uint64_t getTypeHash() const { return getHeader().getTypeHash(); }
   uint32_t getTypeOffset() const { return getHeader().getTypeOffset(); }
 
   void dump(raw_ostream &OS, DIDumpOptions DumpOpts = {}) override;
   // Enable LLVM-style RTTI.
   static bool classof(const DWARFUnit *U) { return U->isTypeUnit(); }
 };
 
 } // end namespace llvm
 
 #endif // LLVM_DEBUGINFO_DWARF_DWARFTYPEUNIT_H

include/llvm/DebugInfo/DWARF/DWARFUnit.h

public:
   unsigned getNumTypesUnits() const { return size() - NumInfoUnits; }
   /// Indicate that parsing .debug_info[.dwo] is done, and remaining units
   /// will be from .debug_types[.dwo].
   void finishedInfoUnits() { NumInfoUnits = size(); }
 
 private:
   void addUnitsImpl(DWARFContext &Context, const DWARFObject &Obj,
                     const DWARFSection &Section, const DWARFDebugAbbrev *DA,
-                    const DWARFSection *RS, StringRef SS,
-                    const DWARFSection &SOS, const DWARFSection *AOS,
-                    const DWARFSection &LS, bool LE, bool IsDWO, bool Lazy,
-                    DWARFSectionKind SectionKind);
+                    const DWARFSection *RS, const DWARFSection *LocSection,
+                    StringRef SS, const DWARFSection &SOS,
+                    const DWARFSection *AOS, const DWARFSection &LS, bool LE,
+                    bool IsDWO, bool Lazy, DWARFSectionKind SectionKind);
 };
 
 /// Represents base address of the CU.
 struct BaseAddress {
   uint64_t Address;
   uint64_t SectionIndex;
 };
 
class DWARFUnit {
   DWARFContext &Context;
   /// Section containing this DWARFUnit.
   const DWARFSection &InfoSection;
 
   DWARFUnitHeader Header;
   const DWARFDebugAbbrev *Abbrev;
   const DWARFSection *RangeSection;
   uint32_t RangeSectionBase;
+  /// We keep track of the location list section's data separately, so we can
+  /// refer to substrings of it when opportune (e.g. in a DWARF package file).
+  std::pair<const DWARFSection *, StringRef> LocSection;
   const DWARFSection &LineSection;
   StringRef StringSection;
   const DWARFSection &StringOffsetSection;
   const DWARFSection *AddrOffsetSection;
   uint32_t AddrOffsetSectionBase = 0;
   bool isLittleEndian;
   bool isDWO;
   const DWARFUnitVector &UnitVector;
protected:
   /// in a dwp file, the start of the unit's contribution to the string offsets
   /// table section (as determined by the index table).
   Optional<StrOffsetsContributionDescriptor>
   determineStringOffsetsTableContributionDWO(DWARFDataExtractor &DA,
                                              uint64_t Offset);
 
 public:
   DWARFUnit(DWARFContext &Context, const DWARFSection &Section,
-            const DWARFUnitHeader &Header,
-            const DWARFDebugAbbrev *DA, const DWARFSection *RS, StringRef SS,
-            const DWARFSection &SOS, const DWARFSection *AOS,
+            const DWARFUnitHeader &Header, const DWARFDebugAbbrev *DA,
+            const DWARFSection *RS, const DWARFSection *LocSection,
+            StringRef SS, const DWARFSection &SOS, const DWARFSection *AOS,
             const DWARFSection &LS, bool LE, bool IsDWO,
             const DWARFUnitVector &UnitVector);
 
   virtual ~DWARFUnit();
 
+  bool isDWOUnit() const { return isDWO; }
   DWARFContext& getContext() const { return Context; }
   const DWARFSection &getInfoSection() const { return InfoSection; }
+  const DWARFSection *getLocSection() const { return LocSection.first; }
+  StringRef getLocSectionData() const { return LocSection.second; }
   uint32_t getOffset() const { return Header.getOffset(); }
   const dwarf::FormParams &getFormParams() const {
     return Header.getFormParams();
   }
   uint16_t getVersion() const { return Header.getVersion(); }
   uint8_t getAddressByteSize() const { return Header.getAddressByteSize(); }
   uint8_t getRefAddrByteSize() const { return Header.getRefAddrByteSize(); }
   uint8_t getDwarfOffsetByteSize() const {

lib/DebugInfo/DWARF/DWARFDie.cpp

DataExtractor Data(StringRef((const char *)Expr.data(), Expr.size()),
                        Ctx.isLittleEndian(), 0);
     DWARFExpression(Data, U->getVersion(), U->getAddressByteSize())
         .print(OS, MRI);
     return;
   }
 
   FormValue.dump(OS, DumpOpts);
   if (FormValue.isFormClass(DWARFFormValue::FC_SectionOffset)) {
-    const DWARFSection &LocSection = Obj.getLocSection();
-    const DWARFSection &LocDWOSection = Obj.getLocDWOSection();
     uint32_t Offset = *FormValue.getAsSectionOffset();
-    if (!LocSection.Data.empty()) {
+    if (!U->isDWOUnit()) {
       DWARFDebugLoc DebugLoc;
-      DWARFDataExtractor Data(Obj, LocSection, Ctx.isLittleEndian(),
+      DWARFDataExtractor Data(Obj, *U->getLocSection(), Ctx.isLittleEndian(),
                               Obj.getAddressSize());
       auto LL = DebugLoc.parseOneLocationList(Data, &Offset);
       if (LL) {
         uint64_t BaseAddr = 0;
         if (Optional<BaseAddress> BA = U->getBaseAddress())
           BaseAddr = BA->Address;
         LL->dump(OS, Ctx.isLittleEndian(), Obj.getAddressSize(), MRI, BaseAddr,
                  Indent);
       } else
         OS << "error extracting location list.";
-    } else if (!LocDWOSection.Data.empty()) {
-      DataExtractor Data(LocDWOSection.Data, Ctx.isLittleEndian(), 0);
+    } else {
+      DataExtractor Data(U->getLocSectionData(), Ctx.isLittleEndian(), 0);
       auto LL = DWARFDebugLocDWO::parseOneLocationList(Data, &Offset);
       if (LL)
         LL->dump(OS, Ctx.isLittleEndian(), Obj.getAddressSize(), MRI, Indent);
       else
         OS << "error extracting location list.";
     }
   }
 }
 
 /// Dump the name encoded in the type tag.
 static void dumpTypeTagName(raw_ostream &OS, dwarf::Tag T) {

lib/DebugInfo/DWARF/DWARFUnit.cpp

 using namespace llvm;
 using namespace dwarf;
 
 void DWARFUnitVector::addUnitsForSection(DWARFContext &C,
                                          const DWARFSection &Section,
                                          DWARFSectionKind SectionKind) {
   const DWARFObject &D = C.getDWARFObj();
   addUnitsImpl(C, D, Section, C.getDebugAbbrev(), &D.getRangeSection(),
-               D.getStringSection(), D.getStringOffsetSection(),
-               &D.getAddrSection(), D.getLineSection(), D.isLittleEndian(),
-               false, false, SectionKind);
+               &D.getLocSection(), D.getStringSection(),
+               D.getStringOffsetSection(), &D.getAddrSection(),
+               D.getLineSection(), D.isLittleEndian(), false, false,
+               SectionKind);
 }
 
 void DWARFUnitVector::addUnitsForDWOSection(DWARFContext &C,
                                             const DWARFSection &DWOSection,
                                             DWARFSectionKind SectionKind,
                                             bool Lazy) {
   const DWARFObject &D = C.getDWARFObj();
   addUnitsImpl(C, D, DWOSection, C.getDebugAbbrevDWO(), &D.getRangeDWOSection(),
-               D.getStringDWOSection(), D.getStringOffsetDWOSection(),
-               &D.getAddrSection(), D.getLineDWOSection(), C.isLittleEndian(),
-               true, Lazy, SectionKind);
+               &D.getLocDWOSection(), D.getStringDWOSection(),
+               D.getStringOffsetDWOSection(), &D.getAddrSection(),
+               D.getLineDWOSection(), C.isLittleEndian(), true, Lazy,
+               SectionKind);
 }
 
 void DWARFUnitVector::addUnitsImpl(
     DWARFContext &Context, const DWARFObject &Obj, const DWARFSection &Section,
-    const DWARFDebugAbbrev *DA, const DWARFSection *RS, StringRef SS,
-    const DWARFSection &SOS, const DWARFSection *AOS, const DWARFSection &LS,
-    bool LE, bool IsDWO, bool Lazy, DWARFSectionKind SectionKind) {
+    const DWARFDebugAbbrev *DA, const DWARFSection *RS,
+    const DWARFSection *LocSection, StringRef SS, const DWARFSection &SOS,
+    const DWARFSection *AOS, const DWARFSection &LS, bool LE, bool IsDWO,
+    bool Lazy, DWARFSectionKind SectionKind) {
   DWARFDataExtractor Data(Obj, Section, LE, 0);
   // Lazy initialization of Parser, now that we have all section info.
   if (!Parser) {
     Parser = [=, &Context, &Obj, &Section, &SOS, &LS](
                  uint32_t Offset, DWARFSectionKind SectionKind,
                  const DWARFSection *CurSection) -> std::unique_ptr<DWARFUnit> {
       const DWARFSection &InfoSection = CurSection ? *CurSection : Section;
       DWARFDataExtractor Data(Obj, InfoSection, LE, 0);
       if (!Data.isValidOffset(Offset))
         return nullptr;
       const DWARFUnitIndex *Index = nullptr;
       if (IsDWO)
         Index = &getDWARFUnitIndex(Context, SectionKind);
       DWARFUnitHeader Header;
       if (!Header.extract(Context, Data, &Offset, SectionKind, Index))
         return nullptr;
       std::unique_ptr<DWARFUnit> U;
       if (Header.isTypeUnit())
         U = llvm::make_unique<DWARFTypeUnit>(Context, InfoSection, Header, DA,
-                                             RS, SS, SOS, AOS, LS, LE, IsDWO,
-                                             *this);
+                                             RS, LocSection, SS, SOS, AOS, LS,
+                                             LE, IsDWO, *this);
       else
         U = llvm::make_unique<DWARFCompileUnit>(Context, InfoSection, Header,
-                                                DA, RS, SS, SOS, AOS, LS, LE,
-                                                IsDWO, *this);
+                                                DA, RS, LocSection, SS, SOS,
+                                                AOS, LS, LE, IsDWO, *this);
       return U;
     };
   }
   if (Lazy)
     return;
   // Find a reasonable insertion point within the vector.  We skip over
   // (a) units from a different section, (b) units from the same section
   // but with lower offset-within-section.  This keeps units in order
DWARFUnitVector::getUnitForIndexEntry(const DWARFUnitIndex::Entry &E) {
 
   auto *NewCU = U.get();
   this->insert(CU, std::move(U));
   ++NumInfoUnits;
   return NewCU;
 }
 
 DWARFUnit::DWARFUnit(DWARFContext &DC, const DWARFSection &Section,
-                     const DWARFUnitHeader &Header,
-                     const DWARFDebugAbbrev *DA, const DWARFSection *RS,
+                     const DWARFUnitHeader &Header, const DWARFDebugAbbrev *DA,
+                     const DWARFSection *RS, const DWARFSection *LocSection,
                      StringRef SS, const DWARFSection &SOS,
                      const DWARFSection *AOS, const DWARFSection &LS, bool LE,
                      bool IsDWO, const DWARFUnitVector &UnitVector)
     : Context(DC), InfoSection(Section), Header(Header), Abbrev(DA),
-      RangeSection(RS), LineSection(LS), StringSection(SS),
-      StringOffsetSection(SOS),  AddrOffsetSection(AOS), isLittleEndian(LE),
-      isDWO(IsDWO), UnitVector(UnitVector) {
+      RangeSection(RS), LocSection(LocSection, LocSection->Data),
+      LineSection(LS), StringSection(SS), StringOffsetSection(SOS),
+      AddrOffsetSection(AOS), isLittleEndian(LE), isDWO(IsDWO),
+      UnitVector(UnitVector) {
   clear();
+  // Adjust the location list data when the location list section is from a
+  // .dwp file.
+  if (auto *IndexEntry = Header.getIndexEntry())
+    if (const auto *C = IndexEntry->getOffset(DW_SECT_LOC))
+      this->LocSection.second =
+          getLocSectionData().substr(C->Offset, C->Length);
 }
 
 DWARFUnit::~DWARFUnit() = default;
 
 DWARFDataExtractor DWARFUnit::getDebugInfoExtractor() const {
   return DWARFDataExtractor(Context.getDWARFObj(), InfoSection, isLittleEndian,
                             getAddressByteSize());
 }
if (getVersion() >= 5) {
           RngListTable = TableOrError.get();
         else
           WithColor::error() << "parsing a range list table: "
                              << toString(TableOrError.takeError())
                              << '\n';
 
         // In a split dwarf unit, there is no DW_AT_rnglists_base attribute.
         // Adjust RangeSectionBase to point past the table header.
         if (isDWO && RngListTable)
           RangeSectionBase = RngListTable->getHeaderSize();
       }
     }
 
     // Don't fall back to DW_AT_GNU_ranges_base: it should be ignored for
     // skeleton CU DIE, so that DWARF users not aware of it are not broken.
   }
 

lib/DebugInfo/DWARF/DWARFVerifier.cpp

if (!verifyUnitHeader(DebugInfoData, &Offset, UnitIdx, UnitType,
       DWARFUnitHeader Header;
       Header.extract(DCtx, DebugInfoData, &OffsetStart, SectionKind);
       DWARFUnit *Unit;
       switch (UnitType) {
       case dwarf::DW_UT_type:
       case dwarf::DW_UT_split_type: {
         Unit = TypeUnitVector.addUnit(llvm::make_unique<DWARFTypeUnit>(
             DCtx, S, Header, DCtx.getDebugAbbrev(), &DObj.getRangeSection(),
-            DObj.getStringSection(), DObj.getStringOffsetSection(),
-            &DObj.getAppleObjCSection(), DObj.getLineSection(),
-            DCtx.isLittleEndian(), false, TypeUnitVector));
+            &DObj.getLocSection(), DObj.getStringSection(),
+            DObj.getStringOffsetSection(), &DObj.getAppleObjCSection(),
+            DObj.getLineSection(), DCtx.isLittleEndian(), false,
+            TypeUnitVector));
         break;
       }
       case dwarf::DW_UT_skeleton:
       case dwarf::DW_UT_split_compile:
       case dwarf::DW_UT_compile:
       case dwarf::DW_UT_partial:
       // UnitType = 0 means that we are verifying a compile unit in DWARF v4.
       case 0: {
         Unit = CompileUnitVector.addUnit(llvm::make_unique<DWARFCompileUnit>(
             DCtx, S, Header, DCtx.getDebugAbbrev(), &DObj.getRangeSection(),
-            DObj.getStringSection(), DObj.getStringOffsetSection(),
-            &DObj.getAppleObjCSection(), DObj.getLineSection(),
-            DCtx.isLittleEndian(), false, CompileUnitVector));
+            &DObj.getLocSection(), DObj.getStringSection(),
+            DObj.getStringOffsetSection(), &DObj.getAppleObjCSection(),
+            DObj.getLineSection(), DCtx.isLittleEndian(), false,
+            CompileUnitVector));
         break;
       }
       default: { llvm_unreachable("Invalid UnitType."); }
       }
       NumDebugInfoErrors += verifyUnitContents(*Unit);
     }
     hasDIE = DebugInfoData.isValidOffset(Offset);
     ++UnitIdx;

test/DebugInfo/Inputs/loclists-dwp-b.ll

+target triple = "x86_64-unknown-linux-gnu"
+
+define dso_local void @_Z1bi(i32 %i) local_unnamed_addr !dbg !7 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %i, metadata !12, metadata !DIExpression()), !dbg !13
+  tail call void asm sideeffect "", "~{rdi},~{dirflag},~{fpsr},~{flags}"() , !dbg !14, !srcloc !15
+  ret void, !dbg !16
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 8.0.0 (https://git.llvm.org/git/clang.git/ 41055c6168135fe539801799e5c5636247cf0302) (https://git.llvm.org/git/llvm.git/ de0558be123ffbb5b5bd692c17dbd57a75fe684f)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "b.cpp", directory: "/home/test/PRs/PR38990")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 8.0.0 (https://git.llvm.org/git/clang.git/ 41055c6168135fe539801799e5c5636247cf0302) (https://git.llvm.org/git/llvm.git/ de0558be123ffbb5b5bd692c17dbd57a75fe684f)"}
+!7 = distinct !DISubprogram(name: "b", linkageName: "_Z1bi", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !11)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !{!12}
+!12 = !DILocalVariable(name: "i", arg: 1, scope: !7, file: !1, line: 1, type: !10)
+!13 = !DILocation(line: 1, column: 12, scope: !7)
+!14 = !DILocation(line: 1, column: 17, scope: !7)
+!15 = !{i32 22}
+!16 = !DILocation(line: 1, column: 38, scope: !7)

test/DebugInfo/X86/loclists-dwp.ll

+; RUN: llc -split-dwarf-file=%t1.dwo -filetype=obj -o %t1.o < %s
+; RUN: llc -split-dwarf-file=%t2.dwo -filetype=obj -o %t2.o < %p/../Inputs/loclists-dwp-b.ll 
+; RUN: llvm-dwp %t1.o %t2.o -o %t.dwp
+; RUN: llvm-dwarfdump -v %t.dwp | FileCheck %s
+
+; Make sure that 2 location lists from different units within a dwp file are 
+; dumped correctly. The 2 location lists differ in the length of their address
+; ranges.
+; 
+; Generate both .ll files with clang -S -emit-llvm from the following sources:
+; a.cpp:
+; void y();
+; void a(int i) {
+;   y();
+;   asm("" : : : "rdi");
+; }
+;
+; b.cpp:
+; void b(int i) { asm("" : : : "rdi"); }
+
+; CHECK:      DW_AT_location [DW_FORM_sec_offset]   (0x00000000
+; CHECK-NEXT: Addr idx 0 (w/ length 6): DW_OP_reg5 RDI)
+
+; CHECK:      DW_AT_location [DW_FORM_sec_offset]   (0x00000000
+; CHECK-NEXT: Addr idx 0 (w/ length 0): DW_OP_reg5 RDI)
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define dso_local void @_Z1ai(i32 %i) local_unnamed_addr !dbg !7 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %i, metadata !12, metadata !DIExpression()), !dbg !13
+  tail call void @_Z1yv(), !dbg !14
+  tail call void asm sideeffect "", "~{rdi},~{dirflag},~{fpsr},~{flags}"(), !dbg !15, !srcloc !16
+  ret void, !dbg !17
+}
+
+declare dso_local void @_Z1yv() local_unnamed_addr
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 8.0.0 (https://git.llvm.org/git/clang.git/ 41055c6168135fe539801799e5c5636247cf0302) (https://git.llvm.org/git/llvm.git/ de0558be123ffbb5b5bd692c17dbd57a75fe684f)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "a.cpp", directory: "/home/test/PRs/PR38990")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 8.0.0 (https://git.llvm.org/git/clang.git/ 41055c6168135fe539801799e5c5636247cf0302) (https://git.llvm.org/git/llvm.git/ de0558be123ffbb5b5bd692c17dbd57a75fe684f)"}
+!7 = distinct !DISubprogram(name: "a", linkageName: "_Z1ai", scope: !1, file: !1, line: 2, type: !8, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !11)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !{!12}
+!12 = !DILocalVariable(name: "i", arg: 1, scope: !7, file: !1, line: 2, type: !10)
+!13 = !DILocation(line: 2, column: 12, scope: !7)
+!14 = !DILocation(line: 3, column: 3, scope: !7)
+!15 = !DILocation(line: 4, column: 3, scope: !7)
+!16 = !{i32 41}
+!17 = !DILocation(line: 5, column: 1, scope: !7)