[clang] [llvm] [MC,llvm-readobj,yaml2obj] Support CREL relocation format (PR #91280)

[Fangrui Song via cfe-commits]

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@@ -1278,29 +1285,69 @@ void ELFState<ELFT>::writeSectionContent(
   if (!Section.Relocations)
     return;
 
+  const bool IsCrel = Section.Type == llvm::ELF::SHT_CREL;
   const bool IsRela = Section.Type == llvm::ELF::SHT_RELA;
+  typename ELFT::uint OffsetMask = 8, Offset = 0, Addend = 0;
+  uint32_t Symidx = 0, Type = 0;
+  uint64_t CurrentOffset = CBA.getOffset();
+  if (IsCrel)
+    for (const ELFYAML::Relocation &Rel : *Section.Relocations)
+      OffsetMask |= Rel.Offset;
+  const int Shift = llvm::countr_zero(OffsetMask);
+  if (IsCrel)
+    CBA.writeULEB128(Section.Relocations->size() * 8 + 4 + Shift);
   for (const ELFYAML::Relocation &Rel : *Section.Relocations) {
     const bool IsDynamic = Section.Link && (*Section.Link == ".dynsym");
-    unsigned SymIdx =
+    uint32_t CurSymidx =
         Rel.Symbol ? toSymbolIndex(*Rel.Symbol, Section.Name, IsDynamic) : 0;
-    if (IsRela) {
+    if (IsCrel) {
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MaskRay wrote:

I've thought about an abstraction. However, the variable and `toSymbolIndex` mechanism are different, making me feel that code sharing would be cumbersome...

https://github.com/llvm/llvm-project/pull/91280