[XRay] Stable sort XRayRecord to remove non-deterministic ordering

Summary:
This fixes failure in tools/llvm-xray/X86/graph-zero-latency-calls.yaml
uncovered by D39245.

Reviewers: dberris

Reviewed By: dberris

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D39943

llvm-svn: 318163

llvm/lib/XRay/Trace.cpp

@@ -606,7 +606,7 @@ Expected<Trace> llvm::xray::loadTraceFile(StringRef Filename, bool Sort) {
   }
 
   if (Sort)
-    std::sort(T.Records.begin(), T.Records.end(),
+    std::stable_sort(T.Records.begin(), T.Records.end(),
               [&](const XRayRecord &L, const XRayRecord &R) {
                 return L.TSC < R.TSC;
               });