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Summary

  1. [RISCV] Fix evaluation of %pcrel_lo (details)
Commit 41449c58c58e466bcf9cdc4f7415950382bad8d7 by roger.ferrer
[RISCV] Fix evaluation of %pcrel_lo
The following testcase
  function:
.Lpcrel_label1:
auipc a0, %pcrel_hi(other_function)
addi a1, a0, %pcrel_lo(.Lpcrel_label1)
.p2align 2          # Causes a new fragment to be emitted
  .type other_function,@function
other_function:
ret
exposes an odd behaviour in which only the %pcrel_hi relocation is
evaluated but not the %pcrel_lo.
  $ llvm-mc -triple riscv64 -filetype obj t.s | llvm-objdump  -d -r -
  <stdin>: file format ELF64-riscv
  Disassembly of section .text:
0000000000000000 function:
        0: 17 05 00 00 auipc a0, 0
        4: 93 05 05 00 mv a1, a0
0000000000000004:  R_RISCV_PCREL_LO12_I other_function+4
  0000000000000008 other_function:
        8: 67 80 00 00 ret
The reason seems to be that in RISCVAsmBackend::shouldForceRelocation we
only consider the fragment but in RISCVMCExpr::evaluatePCRelLo we
consider the section. This usually works but there are cases where the
section may still be the same but the fragment may be another one. In
that case we end forcing a %pcrel_lo relocation without any %pcrel_hi.
This patch makes RISCVAsmBackend::shouldForceRelocation use the section,
if any, to determine if the relocation must be forced or not.
Differential Revision: https://reviews.llvm.org/D60657
The file was addedllvm/test/MC/RISCV/pcrel-fixups.s
The file was modifiedllvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp