[JITLink] Switch from an atom-based model to a "blocks and symbols" model.

In the Atom model the symbols, content and relocations of a relocatable object
file are represented as a graph of atoms, where each Atom represents a
contiguous block of content with a single name (or no name at all if the
content is anonymous), and where edges between Atoms represent relocations.
If more than one symbol is associated with a contiguous block of content then
the content is broken into multiple atoms and layout constraints (represented by
edges) are introduced to ensure that the content remains effectively contiguous.
These layout constraints must be kept in mind when examining the content
associated with a symbol (it may be spread over multiple atoms) or when applying
certain relocation types (e.g. MachO subtractors).

This patch replaces the Atom model in JITLink with a blocks-and-symbols model.
The blocks-and-symbols model represents relocatable object files as bipartite
graphs, with one set of nodes representing contiguous content (Blocks) and
another representing named or anonymous locations (Symbols) within a Block.
Relocations are represented as edges from Blocks to Symbols. This scheme
removes layout constraints (simplifying handling of MachO alt-entry symbols,
and hopefully ELF sections at some point in the future) and simplifies some
relocation logic.

llvm-svn: 373689

1 files changed, 28 insertions, 22 deletions

diff --git a/llvm/lib/ExecutionEngine/JITLink/EHFrameSupportImpl.h b/llvm/lib/ExecutionEngine/JITLink/EHFrameSupportImpl.h
index d679edef7ea..6f9f68ad838 100644
--- a/llvm/lib/ExecutionEngine/JITLink/EHFrameSupportImpl.h
+++ b/llvm/lib/ExecutionEngine/JITLink/EHFrameSupportImpl.h
@@ -21,18 +21,31 @@
 namespace llvm {
 namespace jitlink {
 
-/// A generic parser for eh-frame sections.
+/// A generic binary parser for eh-frame sections.
 ///
-/// Adds atoms representing CIE and FDE entries, using the given FDE-to-CIE and
-/// FDEToTarget relocation kinds.
-class EHFrameParser {
+/// Adds blocks and symbols representing CIE and FDE entries to a JITLink graph.
+///
+/// This parser assumes that the user has already verified that the EH-frame's
+/// address range does not overlap any other section/symbol, so that generated
+/// CIE/FDE records do not overlap other sections/symbols.
+class EHFrameBinaryParser {
 public:
-  EHFrameParser(AtomGraph &G, Section &EHFrameSection, StringRef EHFrameContent,
-                JITTargetAddress EHFrameAddress, Edge::Kind FDEToCIERelocKind,
-                Edge::Kind FDEToTargetRelocKind);
-  Error atomize();
+  EHFrameBinaryParser(JITTargetAddress EHFrameAddress, StringRef EHFrameContent,
+                      unsigned PointerSize, support::endianness Endianness);
+  virtual ~EHFrameBinaryParser() {}
+
+  Error addToGraph();
 
 private:
+  virtual void anchor();
+  virtual Symbol *getSymbolAtAddress(JITTargetAddress Addr) = 0;
+  virtual Symbol &createCIERecord(JITTargetAddress RecordAddr,
+                                  StringRef RecordContent) = 0;
+  virtual Expected<Symbol &>
+  createFDERecord(JITTargetAddress RecordAddr, StringRef RecordContent,
+                  Symbol &CIE, size_t CIEOffset, Symbol &Func,
+                  size_t FuncOffset, Symbol *LSDA, size_t LSDAOffset) = 0;
+
   struct AugmentationInfo {
     bool AugmentationDataPresent = false;
     bool EHDataFieldPresent = false;
@@ -41,31 +54,24 @@ private:
 
   Expected<AugmentationInfo> parseAugmentationString();
   Expected<JITTargetAddress> readAbsolutePointer();
-  Error processCIE();
-  Error processFDE(JITTargetAddress CIEPointerAddress, uint32_t CIEPointer);
+  Error processCIE(size_t RecordOffset, size_t RecordLength);
+  Error processFDE(size_t RecordOffset, size_t RecordLength,
+                   JITTargetAddress CIEPointerOffset, uint32_t CIEPointer);
 
   struct CIEInformation {
     CIEInformation() = default;
-    CIEInformation(DefinedAtom &CIEAtom) : CIEAtom(&CIEAtom) {}
-    DefinedAtom *CIEAtom = nullptr;
+    CIEInformation(Symbol &CIESymbol) : CIESymbol(&CIESymbol) {}
+    Symbol *CIESymbol = nullptr;
     bool FDEsHaveLSDAField = false;
   };
 
-  AtomGraph &G;
-  Section &EHFrameSection;
-  StringRef EHFrameContent;
   JITTargetAddress EHFrameAddress;
+  StringRef EHFrameContent;
+  unsigned PointerSize;
   BinaryStreamReader EHFrameReader;
-  DefinedAtom *CurRecordAtom = nullptr;
   DenseMap<JITTargetAddress, CIEInformation> CIEInfos;
-  Edge::Kind FDEToCIERelocKind;
-  Edge::Kind FDEToTargetRelocKind;
 };
 
-Error addEHFrame(AtomGraph &G, Section &EHFrameSection,
-                 StringRef EHFrameContent, JITTargetAddress EHFrameAddress,
-                 Edge::Kind FDEToCIERelocKind, Edge::Kind FDEToTargetRelocKind);
-
 } // end namespace jitlink
 } // end namespace llvm