[ELF][RISCV] Add R_RISCV_IRELATIVE

[MaskRay]

Summary

https://github.com/riscv/riscv-elf-psabi-doc/pull/131 assigned 58 to R_RISCV_IRELATIVE.

[merge_guards_bot]

Unit tests: unknown.

clang-tidy: pass.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt

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[asb]

Thanks for implementing this - I'd personally like to see the psABI proposal https://github.com/riscv/riscv-elf-psabi-doc/pull/131 merged before merging into LLVM/LLD.

[MaskRay]

Use correct pcrel code sequence for -pie

[MaskRay]

https://github.com/riscv/riscv-elf-psabi-doc/pull/131 was merged. Committing

[MaskRay]

Add psABI link

lld/ELF/Arch/RISCV.cpp

static uint32_t utype(uint32_t op, uint32_t rd, uint32_t imm) {
   return op | (rd << 7) | (imm << 12);
 }
 
 RISCV::RISCV() {
   copyRel = R_RISCV_COPY;
   noneRel = R_RISCV_NONE;
   pltRel = R_RISCV_JUMP_SLOT;
   relativeRel = R_RISCV_RELATIVE;
+  iRelativeRel = R_RISCV_IRELATIVE;
   if (config->is64) {
     symbolicRel = R_RISCV_64;
     tlsModuleIndexRel = R_RISCV_TLS_DTPMOD64;
     tlsOffsetRel = R_RISCV_TLS_DTPREL64;
     tlsGotRel = R_RISCV_TLS_TPREL64;
   } else {
     symbolicRel = R_RISCV_32;
     tlsModuleIndexRel = R_RISCV_TLS_DTPMOD32;

lld/test/ELF/riscv-ifunc-nonpreemptible.s

+# REQUIRES: riscv
+# RUN: llvm-mc -filetype=obj -triple=riscv32 %s -o %t.32.o
+# RUN: ld.lld -pie %t.32.o -o %t.32
+# RUN: llvm-readobj -r %t.32 | FileCheck --check-prefix=RELOC32 %s
+# RUN: llvm-readelf -s %t.32 | FileCheck --check-prefix=SYM32 %s
+# RUN: llvm-objdump -d --no-show-raw-insn %t.32 | FileCheck --check-prefix=DIS32 %s
+
+# RUN: llvm-mc -filetype=obj -triple=riscv64 %s -o %t.64.o
+# RUN: ld.lld -pie %t.64.o -o %t.64
+# RUN: llvm-readobj -r %t.64 | FileCheck --check-prefix=RELOC64 %s
+# RUN: llvm-readelf -s %t.64 | FileCheck --check-prefix=SYM64 %s
+# RUN: llvm-objdump -d --no-show-raw-insn %t.64 | FileCheck --check-prefix=DIS64 %s
+
+# RELOC32:      .rela.dyn {
+# RELOC32-NEXT:   0x3218 R_RISCV_IRELATIVE - 0x117C
+# RELOC32-NEXT: }
+
+# SYM32: 0001190 0 FUNC GLOBAL DEFAULT {{.*}} func
+
+# DIS32:      _start:
+# DIS32-NEXT: 1180: auipc a0, 0
+# DIS32-NEXT:       addi a0, a0, 16
+# DIS32:      Disassembly of section .iplt:
+# DIS32:      func:
+## 32-bit: &.got.plt[func]-. = 0x3218-0x1190 = 4096*2+136
+# DIS32-NEXT: 1190: auipc t3, 2
+# DIS32-NEXT:       lw t3, 136(t3)
+# DIS32-NEXT:       jalr t1, t3
+# DIS32-NEXT:       nop
+
+# RELOC64:      .rela.dyn {
+# RELOC64-NEXT:   0x3370 R_RISCV_IRELATIVE - 0x1260
+# RELOC64-NEXT: }
+
+# SYM64: 000000000001270 0 FUNC GLOBAL DEFAULT {{.*}} func
+
+# DIS64:      _start:
+# DIS64-NEXT: 1264: auipc a0, 0
+# DIS64-NEXT:       addi a0, a0, 12
+# DIS64:      Disassembly of section .iplt:
+# DIS64:      func:
+## 64-bit: &.got.plt[func]-. = 0x3370-0x1270 = 4096*2+256
+# DIS64-NEXT: 1270: auipc t3, 2
+# DIS64-NEXT:       ld t3, 256(t3)
+# DIS64-NEXT:       jalr t1, t3
+# DIS64-NEXT:       nop
+
+.text
+.globl func
+.type func, @gnu_indirect_function
+func:
+  ret
+
+.globl _start
+_start:
+.L:
+  auipc a0, %pcrel_hi(func)
+  addi a0, a0, %pcrel_lo(.L)

llvm/include/llvm/BinaryFormat/ELFRelocs/RISCV.def

 ELF_RELOC(R_RISCV_TPREL_S,           50)
 ELF_RELOC(R_RISCV_RELAX,             51)
 ELF_RELOC(R_RISCV_SUB6,              52)
 ELF_RELOC(R_RISCV_SET6,              53)
 ELF_RELOC(R_RISCV_SET8,              54)
 ELF_RELOC(R_RISCV_SET16,             55)
 ELF_RELOC(R_RISCV_SET32,             56)
 ELF_RELOC(R_RISCV_32_PCREL,          57)
+ELF_RELOC(R_RISCV_IRELATIVE,         58)