[llvm] [llvm-gsymutil] Ensure gSYM creation determinism with merged functions (PR #122921)

[via llvm-commits]

https://github.com/alx32 created https://github.com/llvm/llvm-project/pull/122921

We were seeing occasional test failures with expensive checks enabled. The issue was tracked down to a `sort` which should instead be a `stable_sort` to ensure determinism. Checked locally and the non-determinism went away. 

>From 3d361b798fad33a34ba4015194c155f40ca5c799 Mon Sep 17 00:00:00 2001
From: Alex B <alexborcan at meta.com>
Date: Tue, 14 Jan 2025 07:32:20 -0800
Subject: [PATCH] [llvm-gsymutil] Ensure gSYM creation determinism with merged
 functions

---
 llvm/lib/DebugInfo/GSYM/GsymCreator.cpp | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/DebugInfo/GSYM/GsymCreator.cpp b/llvm/lib/DebugInfo/GSYM/GsymCreator.cpp
index 14078f5aaf9a46..f24f8c72ef0a27 100644
--- a/llvm/lib/DebugInfo/GSYM/GsymCreator.cpp
+++ b/llvm/lib/DebugInfo/GSYM/GsymCreator.cpp
@@ -268,15 +268,25 @@ llvm::Error GsymCreator::finalize(OutputAggregator &Out) {
   // we wouldn't find any function for range (end of Y, end of X)
   // with binary search
 
+  //////////////////////////////////////////////////////////////////////////////
+  llvm::outs() << "MyLog: Before sort:\n";
+  for (const auto &FuncInfo : Funcs) {
+    llvm::outs() << FuncInfo.Name << " " << getString(FuncInfo.Name) << "\n";
+  }
+  llvm::outs() << "\n\n";
+  //////////////////////////////////////////////////////////////////////////////
+
   const auto NumBefore = Funcs.size();
+
   // Only sort and unique if this isn't a segment. If this is a segment we
   // already finalized the main GsymCreator with all of the function infos
   // and then the already sorted and uniqued function infos were added to this
   // object.
   if (!IsSegment) {
     if (NumBefore > 1) {
-      // Sort function infos so we can emit sorted functions.
-      llvm::sort(Funcs);
+      // Sort function infos so we can emit sorted functions. Use stable sort to
+      // ensure determinism.
+      llvm::stable_sort(Funcs);
       std::vector<FunctionInfo> FinalizedFuncs;
       FinalizedFuncs.reserve(Funcs.size());
       FinalizedFuncs.emplace_back(std::move(Funcs.front()));
@@ -335,6 +345,15 @@ llvm::Error GsymCreator::finalize(OutputAggregator &Out) {
       }
       std::swap(Funcs, FinalizedFuncs);
     }
+
+    //////////////////////////////////////////////////////////////////////////////
+    llvm::outs() << "MyLog: After sort:\n";
+    for (const auto &FuncInfo : Funcs) {
+      llvm::outs() << FuncInfo.Name << " " << getString(FuncInfo.Name) << "\n";
+    }
+    llvm::outs() << "\n\n";
+    //////////////////////////////////////////////////////////////////////////////
+
     // If our last function info entry doesn't have a size and if we have valid
     // text ranges, we should set the size of the last entry since any search for
     // a high address might match our last entry. By fixing up this size, we can