[debuginfo][coro] Fix linkage name for clones of coro functions (#141889)

So far, the `DW_AT_linkage_name` of the coroutine `resume`, `destroy`,
`cleanup` and `noalloc` function clones were incorrectly set to the
original function name instead of the updated function names.

With this commit, we now update the `DW_AT_linkage_name` to the correct
name. This has multiple benefits:

1. it's easier for me (and other toolchain developers) to understand the
   output of `llvm-dwarf-dump` when coroutines are involved.
2. When hitting a breakpoint, both LLDB and GDB now tell you which clone
   of the function you are in. E.g., GDB now prints "Breakpoint 1.2,
   coro_func(int) [clone .resume] (v=43) at ..." instead of "Breakpoint
   1.2, coro_func(int) (v=43) at ...".
3. GDB's `info line coro_func` command now allows you to distinguish the
   multiple different clones of the function.

In Swift, the linkage names of the clones were already updated. The
comment right above the relevant code in `CoroSplit.cpp` already hinted
that the linkage name should probably also be updated in C++. This
comment was added in commit 6ce76ff7eb7640, and back then the
corresponding `DW_AT_specification` (i.e., `SP->getDeclaration()`) was
not updated, yet, which led to problems for C++. In the meantime, commit
ca1a5b37c7236d added code to also update `SP->getDeclaration`, as such
there is no reason anymore to not update the linkage name for C++.

Note that most test cases used inconsistent function names for the LLVM
function vs. the DISubprogram linkage name. clang would never emit such
LLVM IR. This confused me initially, and hence I fixed it while updating
the test case.

Drive-by fix: The change in `CGVTables.cpp` is purely stylistic, NFC.
When looking for other usages of `replaceWithDistinct`, I got initially
confused because `CGVTables.cpp` was calling a static function via an
object instance.

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index c744727..2897ccd 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -124,7 +124,7 @@ static void resolveTopLevelMetadata(llvm::Function *Fn,
   auto *DIS = Fn->getSubprogram();
   if (!DIS)
     return;
-  auto *NewDIS = DIS->replaceWithDistinct(DIS->clone());
+  auto *NewDIS = llvm::MDNode::replaceWithDistinct(DIS->clone());
   VMap.MD()[DIS].reset(NewDIS);
 
   // Find all llvm.dbg.declare intrinsics and resolve the DILocalVariable nodes