[lld] [lld] Add infrastructure for handling RISCV vendor-specific relocations. (PR #159987)

[Sam Elliott via llvm-commits]

================
@@ -1476,3 +1482,80 @@ void elf::mergeRISCVAttributesSections(Ctx &ctx) {
 }
 
 void elf::setRISCVTargetInfo(Ctx &ctx) { ctx.target.reset(new RISCV(ctx)); }
+
+class RISCVRelocScan : public RelocScan {
+public:
+  StringRef rvVendor;
+
+  RISCVRelocScan(Ctx &ctx, InputSectionBase *sec = nullptr)
+      : RelocScan(ctx, sec) {}
+  template <class ELFT, class RelTy>
+  void scan(typename Relocs<RelTy>::const_iterator &it, RelType type,
+            int64_t addend);
+};
+
+template <class ELFT, class RelTy>
+void RISCVRelocScan::scan(typename Relocs<RelTy>::const_iterator &it,
+                          RelType type, int64_t addend) {
+  const RelTy &rel = *it;
+  uint32_t symIndex = rel.getSymbol(false);
+  Symbol &sym = sec->getFile<ELFT>()->getSymbol(symIndex);
+
+  if (type == R_RISCV_VENDOR) {
+    if (!rvVendor.empty())
+      Err(ctx) << "found consecutive R_RISCV_VENDOR relocations";
----------------
lenary wrote:

We should probably test this case.

https://github.com/llvm/llvm-project/pull/159987