[all-commits] [llvm/llvm-project] 3a6a80: [Clang][Coroutine][DebugInfo] In c++ coroutine, cl...

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  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3a6a80b641bcffc570d5bc187b45f7bb9a2e7ce2
      https://github.com/llvm/llvm-project/commit/3a6a80b641bcffc570d5bc187b45f7bb9a2e7ce2
  Author: yifeng.dongyifeng <yifeng.dongyifeng at alibaba-inc.com>
  Date:   2021-04-12 (Mon, 12 Apr 2021)

  Changed paths:
    M clang/lib/CodeGen/CGCoroutine.cpp
    M clang/lib/CodeGen/CGDebugInfo.cpp
    M clang/lib/CodeGen/CGDebugInfo.h
    M clang/lib/CodeGen/CGDecl.cpp
    M clang/lib/CodeGen/CodeGenFunction.cpp
    M clang/lib/CodeGen/CodeGenFunction.h
    A clang/test/CodeGenCoroutines/coro-dwarf.cpp

  Log Message:
  -----------
  [Clang][Coroutine][DebugInfo] In c++ coroutine, clang will emit different debug info variables for parameters and move-parameters.

The first one is the real parameters of the coroutine function, the
other one just for copying parameters to the coroutine frame.

Considering the following c++ code:
```
struct coro {
  ...
};

coro foo(struct test & t) {
  ...
  co_await suspend_always();
    ...
    co_await suspend_always();
    ...
    co_await suspend_always();
}

int main(int argc, char *argv[]) {
  auto c = foo(...);
    c.handle.resume();
      ...
  }
```

Function foo is the standard coroutine function, and it has only
one parameter named t (ignoring this at first),
when we use the llvm code to compile this function, we can get the
following ir:

```
!2921 = distinct !DISubprogram(name: "foo", linkageName:
"_ZN6Object3fooE4test", scope: !2211, file: !45, li\
ne: 48, type: !2329, scopeLine: 48, flags: DIFlagPrototyped |
DIFlagAllCallsDescribed, spFlags: DISPFlagDefi\
nition | DISPFlagOptimized, unit: !44, declaration: !2328,
retainedNodes: !2922)
!2924 = !DILocalVariable(name: "t", arg: 2, scope: !2921, file: !45,
line: 48, type: !838)
...
!2926 = !DILocalVariable(name: "t", scope: !2921, type: !838, flags:
DIFlagArtificial)
```
We can find there are two `the same` DIVariable named t in the same
dwarf scope for foo.resume.
And when we try to use llvm-dwarfdump to dump the dwarf info of this
elf, we get the following output:

```
0x00006684:   DW_TAG_subprogram
                DW_AT_low_pc    (0x00000000004013a0)
                DW_AT_high_pc   (0x00000000004013a8)
                DW_AT_frame_base        (DW_OP_reg7 RSP)
                DW_AT_object_pointer    (0x0000669c)
                DW_AT_GNU_all_call_sites        (true)
                DW_AT_specification     (0x00005b5c "_ZN6Object3fooE4test")

0x000066a5:     DW_TAG_formal_parameter
                DW_AT_name    ("t")
                DW_AT_decl_file       ("/disk1/yifeng.dongyifeng/my_code/llvm/build/bin/coro-debug-1.cpp")
                DW_AT_decl_line       (48)
                DW_AT_type    (0x00004146 "test")

0x000066ba:     DW_TAG_variable
                  DW_AT_name    ("t")
                  DW_AT_type    (0x00004146 "test")
                  DW_AT_artificial      (true)
```
The elf also has two 't' in the same scope.
But unluckily, it might let the debugger
confused. And failed to print parameters for O0 or above.
This patch will make coroutine parameters and move
parameters use the same DIVar and try to fix the problems
that I mentioned before.

Test Plan: check-clang

Reviewed By: aprantl, jmorse

Differential Revision: https://reviews.llvm.org/D97533