[LoongArch] Add R_LARCH_MARK_LA relocation for la.abs

Match gas behavior: generate `R_LARCH_MARK_LA` relocation for `la.abs`.

Reviewers: heiher, SixWeining

Reviewed By: SixWeining, heiher

Pull Request: #161062

Author: wangleiat

llvm/lib/ExecutionEngine/JITLink/ELF_loongarch.cpp

@@ -365,6 +365,10 @@ class ELFLinkGraphBuilder_loongarch : public ELFLinkGraphBuilder<ELFT> {
     uint32_t Type = Rel.getType(false);
     int64_t Addend = Rel.r_addend;
 
+    // ignore
+    if (Type == ELF::R_LARCH_MARK_LA)
+      return Error::success();
+
     if (Type == ELF::R_LARCH_RELAX) {
       if (BlockToFix.edges_empty())
         return make_error<StringError>(

llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp

@@ -781,6 +781,9 @@ void RuntimeDyldELF::resolveLoongArch64Relocation(const SectionEntry &Section,
   default:
     report_fatal_error("Relocation type not implemented yet!");
     break;
+  case ELF::R_LARCH_MARK_LA:
+    // ignore
+    break;
   case ELF::R_LARCH_32:
     support::ulittle32_t::ref{TargetPtr} =
         static_cast<uint32_t>(Value + Addend);

llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp

@@ -957,8 +957,10 @@ void LoongArchAsmParser::emitLoadAddressAbs(MCInst &Inst, SMLoc IDLoc,
                              : Inst.getOperand(2).getExpr();
   InstSeq Insts;
 
+  // To distinguish between la.abs and %abs_hi20, la.abs will generate
+  // R_LARCH_MARK_LA and R_LARCH_ABS_HI20 relocations.
   Insts.push_back(
-      LoongArchAsmParser::Inst(LoongArch::LU12I_W, ELF::R_LARCH_ABS_HI20));
+      LoongArchAsmParser::Inst(LoongArch::LU12I_W, ELF::R_LARCH_MARK_LA));
   Insts.push_back(
       LoongArchAsmParser::Inst(LoongArch::ORI, ELF::R_LARCH_ABS_LO12));
 

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCAsmInfo.cpp

@@ -32,6 +32,7 @@ static StringRef getLoongArchSpecifierName(uint16_t S) {
     return "b16";
   case ELF::R_LARCH_B21:
     return "b21";
+  case ELF::R_LARCH_MARK_LA:
   case ELF::R_LARCH_ABS_HI20:
     return "abs_hi20";
   case ELF::R_LARCH_ABS_LO12:

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp

@@ -161,6 +161,13 @@ LoongArchMCCodeEmitter::getExprOpValue(const MCInst &MI, const MCOperand &MO,
     case ELF::R_LARCH_B26:
       FixupKind = LoongArch::fixup_loongarch_b26;
       break;
+    case ELF::R_LARCH_MARK_LA:
+      // Match gas behavior: generate `R_LARCH_MARK_LA` relocation when using
+      // `la.abs`.
+      Fixups.push_back(
+          MCFixup::create(0, MCConstantExpr::create(0, Ctx),
+                          FirstLiteralRelocationKind + ELF::R_LARCH_MARK_LA));
+      [[fallthrough]];
     case ELF::R_LARCH_ABS_HI20:
       FixupKind = LoongArch::fixup_loongarch_abs_hi20;
       break;

llvm/test/MC/LoongArch/Macros/macros-la.s

@@ -26,6 +26,7 @@ la.abs $a0, sym_abs
 # ABS-NEXT:   lu32i.d $a0, %abs64_lo20(sym_abs)
 # ABS-NEXT:   lu52i.d $a0, $a0, %abs64_hi12(sym_abs)
 # ABS-EMPTY:
+# RELOC-NEXT: R_LARCH_MARK_LA - 0x0
 # RELOC-NEXT: R_LARCH_ABS_HI20 sym_abs 0x0
 # RELOC-NEXT: R_LARCH_ABS_LO12 sym_abs 0x0
 # RELOC-NEXT: R_LARCH_ABS64_LO20 sym_abs 0x0