[all-commits] [llvm/llvm-project] 565a1f: [AArch64] Unconditionally use DW_EH_PE_indirect|DW...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 565a1fb1334b8cf510af1338cae3f50815a99f90
      https://github.com/llvm/llvm-project/commit/565a1fb1334b8cf510af1338cae3f50815a99f90
  Author: Fangrui Song <i at maskray.me>
  Date:   2023-02-03 (Fri, 03 Feb 2023)

  Changed paths:
    M llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
    M llvm/test/CodeGen/AArch64/arm64-big-endian-eh.ll
    M llvm/test/CodeGen/AArch64/pic-eh-stubs.ll
    M llvm/test/DebugInfo/AArch64/eh_frame_personality.ll
    M llvm/test/Transforms/CodeGenPrepare/AArch64/large-offset-gep.ll

  Log Message:
  -----------
  [AArch64] Unconditionally use DW_EH_PE_indirect|DW_EH_PE_pcrel personality/lsda/ttype encodings

For -fno-pic, without DW_EH_PE_indirect, the personality routine pointer in a
CIE needs an R_AARCH64_ABS64 relocation. In common configurations that
`__gcc_personality_v0` is defined in a shared object, this will lead to a
discouraged canonical PLT entry, or, if `ld.lld -z notext` (betwen D122459 and
D143136), a dynamic R_AARCH64_ABS64 relocation with an incorrect offset:
https://github.com/llvm/llvm-project/issues/60392

Since GCC uses DW_EH_PE_indirect for -fno-pic code (the behavior hasn't changed
since the initial port in 2012), let's follow suit by simplifying the code.
(
For tiny and small code models, we use DW_EH_PE_sdata8 instead of GCC's
DW_EH_PE_sdata4. This is a deliberate choice to support personality-.eh_frame
offset > 2GiB. This is necessary for small code model since "Max text segment
size < 2GiB" but it is unnecessary to make `-fno-pic -mcmodel={tiny,small}`
different: The scenarios that uses both -fno-pic and C++ exceptions have been
increasingly rare now, so there is little advantage optimizing for the little
size saving with code complexity.
)

Reviewed By: MatzeB

Differential Revision: https://reviews.llvm.org/D143039