[all-commits] [llvm/llvm-project] 3329ce: [DebugInfo] Don't join DW_AT_comp_dir and director...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3329cec2f79185bafd678f310fafadba2a8c76d2
      https://github.com/llvm/llvm-project/commit/3329cec2f79185bafd678f310fafadba2a8c76d2
  Author: Fangrui Song <i at maskray.me>
  Date:   2022-08-12 (Fri, 12 Aug 2022)

  Changed paths:
    M llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
    M llvm/test/DebugInfo/X86/symbolize_function_start_v5.s
    M llvm/test/MC/ELF/debug-prefix-map.s

  Log Message:
  -----------
  [DebugInfo] Don't join DW_AT_comp_dir and directories[0] for DWARF v5 line tables

DWARF v5 6.2.4 The Line Number Program Header says:

> The first entry is the current directory of the compilation. Each additional
> path entry is either a full path name or is relative to the current directory of
> the compilation.

When forming a path, relative DW_AT_comp_dir and directories[0] are not supposed
to be joined together. Fix getFileNameByIndex to special case DWARF v5 DirIdx == 0.

Reviewed By: #debug-info, dblaikie

Differential Revision: https://reviews.llvm.org/D131804