[all-commits] [llvm/llvm-project] a5c8ec: [CGDebugInfo] Emit subprograms for decls when AT_t...

[Vedant Kumar via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: a5c8ec4baa2c00d8dbca36ffd236a40f9e0c07ed
      https://github.com/llvm/llvm-project/commit/a5c8ec4baa2c00d8dbca36ffd236a40f9e0c07ed
  Author: Vedant Kumar <vsk at apple.com>
  Date:   2019-11-04 (Mon, 04 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:
  -----------
  [CGDebugInfo] Emit subprograms for decls when AT_tail_call is understood

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