[llvm] [RISCV] Vendor Relocations for Xqci extension (PR #135400)

[Fangrui Song via llvm-commits]

================
@@ -611,6 +612,44 @@ bool RISCVAsmBackend::evaluateTargetFixup(const MCFixup &Fixup,
          isPCRelFixupResolved(AUIPCTarget.getAddSym(), *AUIPCDF);
 }
 
+std::optional<StringRef>
+RISCVAsmBackend::getVendorIdentifierForFixup(unsigned FixupKind) const {
+  switch (FixupKind) {
+  case RISCV::fixup_riscv_qc_e_branch:
+  case RISCV::fixup_riscv_qc_abs20_u:
+  case RISCV::fixup_riscv_qc_e_32:
+  case RISCV::fixup_riscv_qc_e_jump_plt:
+    return "QUALCOMM";
+  }
+
+  return std::nullopt;
+}
+
+void RISCVAsmBackend::addVendorReloc(const MCFragment &F, const MCFixup &Fixup,
+                                     StringRef VendorIdentifier) {
+  MCContext &Ctx = Asm->getContext();
+
+  auto It = VendorSymbols.find(VendorIdentifier);
+  if (It == VendorSymbols.end()) {
+    MCSymbol *VendorSymbol = Ctx.createLocalSymbol(VendorIdentifier);
+    VendorSymbol->setVariableValue(MCConstantExpr::create(0, Ctx));
+    Asm->registerSymbol(*VendorSymbol);
+
+    It = VendorSymbols.try_emplace(VendorIdentifier, VendorSymbol).first;
+  }
+
+  MCSymbol *VendorSymbol = It->getValue();
+  const MCExpr *VendorExpr = MCSymbolRefExpr::create(VendorSymbol, Ctx);
+  MCFixup VendorFixup =
+      MCFixup::create(Fixup.getOffset(), VendorExpr,
+                      FirstLiteralRelocationKind + ELF::R_RISCV_VENDOR);
----------------
MaskRay wrote:

s/FirstLiteralRelocationKind + ELF::R_RISCV_VENDOR/ELF::R_RISCV_VENDOR/`

https://github.com/llvm/llvm-project/pull/135400