[all-commits] [llvm/llvm-project] 5b9a07: Revert a5c8ec4 "[CGDebugInfo] Emit subprograms for...

[Hans via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 5b9a072c39c0c34a290abd19e4aca8208a9afae6
      https://github.com/llvm/llvm-project/commit/5b9a072c39c0c34a290abd19e4aca8208a9afae6
  Author: Hans Wennborg <hans at chromium.org>
  Date:   2019-11-07 (Thu, 07 Nov 2019)

  Changed paths:
    M clang/lib/CodeGen/CGDebugInfo.cpp
    M clang/test/CodeGen/debug-info-extern-call.c
    M clang/test/CodeGenCXX/dbg-info-all-calls-described.cpp
    M llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll

  Log Message:
  -----------
  Revert a5c8ec4 "[CGDebugInfo] Emit subprograms for decls when AT_tail_call is understood"

This caused Chromium builds to fail with "inlinable function call in a function
with debug info must have a !dbg location" errors. See
https://bugs.chromium.org/p/chromium/issues/detail?id=1022296#c1 for a
reproducer.

> Currently, clang emits subprograms for declared functions when the
> target debugger or DWARF standard is known to support entry values
> (DW_OP_entry_value & the GNU equivalent).
>
> Treat DW_AT_tail_call the same way to allow debuggers to follow cross-TU
> tail calls.
>
> Pre-patch debug session with a cross-TU tail call:
>
> ```
>   * frame #0: 0x0000000100000fa4 main`target at b.c:4:3 [opt]
>     frame #1: 0x0000000100000f99 main`main at a.c:8:10 [opt]
> ```
>
> Post-patch (note that the tail-calling frame, "helper", is visible):
>
> ```
>   * frame #0: 0x0000000100000fa4 main`target at b.c:4:3 [opt]
>     frame #1: 0x0000000100000f80 main`helper [opt] [artificial]
>     frame #2: 0x0000000100000f99 main`main at a.c:8:10 [opt]
> ```
>
> rdar://46577651
>
> Differential Revision: https://reviews.llvm.org/D69743