[LoongArch] Add R_LARCH_MARK_LA relocation for la.abs

[wangleiat]

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

[llvmbot]

@llvm/pr-subscribers-backend-loongarch

@llvm/pr-subscribers-backend-risc-v

Author: wanglei (wangleiat)

Changes

The relocation is used for edk2 builds.

---

Full diff: https://github.com/llvm/llvm-project/pull/161062.diff

6 Files Affected:

• (modified) llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp (+4)
• (modified) llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp (+3)
• (modified) llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp (+3-1)
• (modified) llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCAsmInfo.cpp (+1)
• (modified) llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp (+6)
• (modified) llvm/test/MC/LoongArch/Macros/macros-la.s (+1)

diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp
index 0dc97104610bb..b3f7a443d2238 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp
@@ -919,6 +919,10 @@ class ELFLinkGraphBuilder_riscv : 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_RISCV_RELAX) {
       if (BlockToFix.edges_empty())
         return make_error<StringError>(
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
index d6268037dea86..dd1b1d3b2e943 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
+++ b/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);
diff --git a/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp b/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
index 5be4713b349ee..9b11201d0312d 100644
--- a/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
+++ b/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));
 
diff --git a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCAsmInfo.cpp b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCAsmInfo.cpp
index 0d7761777cb7d..8ecb62d0ea7bb 100644
--- a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCAsmInfo.cpp
+++ b/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:
diff --git a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp
index b7ead5e61ab81..603c6f77f05dc 100644
--- a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp
+++ b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp
@@ -161,6 +161,12 @@ 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:
+      // The R_LARCH_MARCH_LA is used for LoongArch edk2 builds.
+      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;
diff --git a/llvm/test/MC/LoongArch/Macros/macros-la.s b/llvm/test/MC/LoongArch/Macros/macros-la.s
index a732988ef1f1a..8022d5b038880 100644
--- a/llvm/test/MC/LoongArch/Macros/macros-la.s
+++ b/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

[heiher]

LGTM.

[heiher]

In the la-abi-specs, R_LARCH_MARK_LA is described as being used to mark la.abs. Should this be backported to LLVM 21?

[SixWeining]

About the comments and the commit message: I don't want to tie this relocation to specific applications (edk2) because we don't know if there is any other user.

[wangleiat]

In the la-abi-specs, R_LARCH_MARK_LA is described as being used to mark la.abs. Should this be backported to LLVM 21?

This is not actually required — it’s defined in ABI 1.0 and no longer used in 2.0. The relocation is generated only to satisfy specific software requirements (not an urgent need).