[llvm] fix(gcov): write current_working_directory to .gcno file (PR #121369)

[via llvm-commits]

https://github.com/PikachuHyA created https://github.com/llvm/llvm-project/pull/121369

fix https://github.com/llvm/llvm-project/issues/121368

>From 5079a359aae0e0e342c51c5cb84a4858ba047a0b Mon Sep 17 00:00:00 2001
From: PikachuHy <pikachuhy at linux.alibaba.com>
Date: Tue, 31 Dec 2024 10:17:04 +0800
Subject: [PATCH] fix(gcov): write current_working_directory to .gcno file

---
 llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
index f9be7f933d31e4..fe476038498194 100644
--- a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
@@ -973,8 +973,13 @@ bool GCOVProfiler::emitProfileNotes(
         out.write(Tmp, 4);
       }
       write(Stamp);
-      if (Version >= 90)
-        writeString(""); // unuseful current_working_directory
+      if (Version >= 90) {
+        SmallString<256> CWD;
+        llvm::sys::fs::current_path(CWD);
+        // the current_working_directory is used by gcov
+        // if the source file is relative path
+        writeString(CWD);
+      }
       if (Version >= 80)
         write(0); // unuseful has_unexecuted_blocks