[DWARF v5] Rework of string offsets table reader

Reorganizes the DWARF consumer to derive the string offsets table 
contribution's format from the contribution header instead of 
(incorrectly) from the unit's format.

Reviewers: JDevliegehere, aprantl

Differential Revision: https://reviews.llvm.org/D41146
 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321295 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 55 insertions, 1 deletions

diff --git a/include/llvm/DebugInfo/DWARF/DWARFUnit.h b/include/llvm/DebugInfo/DWARF/DWARFUnit.h
index e9178e03fa8..09356ade8ef 100644
--- a/include/llvm/DebugInfo/DWARF/DWARFUnit.h
+++ b/include/llvm/DebugInfo/DWARF/DWARFUnit.h
@@ -165,6 +165,29 @@ struct BaseAddress {
   uint64_t SectionIndex;
 };
 
+/// Represents a unit's contribution to the string offsets table.
+struct StrOffsetsContributionDescriptor {
+  uint64_t Base = 0;
+  uint64_t Size = 0;
+  /// Format and version.
+  DWARFFormParams FormParams = {0, 0, dwarf::DwarfFormat::DWARF32};
+
+  StrOffsetsContributionDescriptor(uint64_t Base, uint64_t Size,
+                                   uint8_t Version, dwarf::DwarfFormat Format)
+      : Base(Base), Size(Size), FormParams({Version, 0, Format}) {}
+
+  uint8_t getVersion() const { return FormParams.Version; }
+  dwarf::DwarfFormat getFormat() const { return FormParams.Format; }
+  uint8_t getDwarfOffsetByteSize() const {
+    return FormParams.getDwarfOffsetByteSize();
+  }
+  /// Determine whether a contribution to the string offsets table is
+  /// consistent with the relevant section size and that its length is
+  /// a multiple of the size of one of its entries.
+  Optional<StrOffsetsContributionDescriptor>
+  validateContributionSize(DWARFDataExtractor &DA);
+};
+
 class DWARFUnit {
   DWARFContext &Context;
   /// Section containing this DWARFUnit.
@@ -176,7 +199,6 @@ class DWARFUnit {
   const DWARFSection &LineSection;
   StringRef StringSection;
   const DWARFSection &StringOffsetSection;
-  uint64_t StringOffsetSectionBase = 0;
   const DWARFSection *AddrOffsetSection;
   uint32_t AddrOffsetSectionBase = 0;
   bool isLittleEndian;
@@ -185,6 +207,9 @@ class DWARFUnit {
 
   // Version, address size, and DWARF format.
   DWARFFormParams FormParams;
+  /// Start, length, and DWARF format of the unit's contribution to the string
+  /// offsets table (DWARF v5).
+  Optional<StrOffsetsContributionDescriptor> StringOffsetsTableContribution;
 
   uint32_t Offset;
   uint32_t Length;
@@ -219,6 +244,21 @@ protected:
   /// Size in bytes of the unit header.
   virtual uint32_t getHeaderSize() const { return getVersion() <= 4 ? 11 : 12; }
 
+  /// Find the unit's contribution to the string offsets table and determine its
+  /// length and form. The given offset is expected to be derived from the unit
+  /// DIE's DW_AT_str_offsets_base attribute.
+  Optional<StrOffsetsContributionDescriptor>
+  determineStringOffsetsTableContribution(DWARFDataExtractor &DA,
+                                          uint64_t Offset);
+
+  /// Find the unit's contribution to the string offsets table and determine its
+  /// length and form. The given offset is expected to be 0 in a dwo file or,
+  /// 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 DWARFDebugAbbrev *DA, const DWARFSection *RS, StringRef SS,
@@ -272,6 +312,10 @@ public:
   uint32_t getNextUnitOffset() const { return Offset + Length + 4; }
   uint32_t getLength() const { return Length; }
 
+  const Optional<StrOffsetsContributionDescriptor> &
+  getStringOffsetsTableContribution() const {
+    return StringOffsetsTableContribution;
+  }
   const DWARFFormParams &getFormParams() const { return FormParams; }
   uint16_t getVersion() const { return FormParams.Version; }
   dwarf::DwarfFormat getFormat() const { return FormParams.Format; }
@@ -281,6 +325,16 @@ public:
     return FormParams.getDwarfOffsetByteSize();
   }
 
+  uint8_t getDwarfStringOffsetsByteSize() const {
+    assert(StringOffsetsTableContribution);
+    return StringOffsetsTableContribution->getDwarfOffsetByteSize();
+  }
+
+  uint64_t getStringOffsetsBase() const {
+    assert(StringOffsetsTableContribution);
+    return StringOffsetsTableContribution->Base;
+  }
+
   const DWARFAbbreviationDeclarationSet *getAbbreviations() const;
 
   uint8_t getUnitType() const { return UnitType; }