[MemProf] Fix callee guid for non-leaf frame (#172502)

When matching callsite profile info, we synthesize VP metadata for
matched indirect calls from the CalleeGuids recorded with the CallSite
profile info. However, those are the callee guids of the leaf-most frame
in the callsite. In cases where we match to a portion of the frames, not
including the leaf, the callee guid should instead be synthesized from
the next leaf-most frame in the list.

This addresses the case where indirect call promotion was applied in the
profiled binary during SamplePGO matching in a ThinLTO backend, where we
didn't have VP metadata.

1 files changed, 8 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp b/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp
index 5cde52637248..1a55021c5d3f 100644
--- a/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemProfUse.cpp
@@ -702,8 +702,14 @@ readMemprof(Module &M, Function &F, IndexedInstrProfReader *MemProfReader,
     for (auto &StackFrame : CS.Frames) {
       uint64_t StackId = computeStackId(StackFrame);
       ArrayRef<Frame> FrameSlice = ArrayRef<Frame>(CS.Frames).drop_front(Idx++);
-      ArrayRef<GlobalValue::GUID> CalleeGuids(CS.CalleeGuids);
-      LocHashToCallSites[StackId].push_back({FrameSlice, CalleeGuids});
+      // The callee guids for the slice containing all frames (due to the
+      // increment above Idx is now 1) comes from the CalleeGuids recorded in
+      // the CallSite. For the slices not containing the leaf-most frame, the
+      // callee guid is simply the function GUID of the prior frame.
+      LocHashToCallSites[StackId].push_back(
+          {FrameSlice, (Idx == 1 ? CS.CalleeGuids
+                                 : ArrayRef<GlobalValue::GUID>(
+                                       CS.Frames[Idx - 2].Function))});
 
       ProfileHasColumns |= StackFrame.Column;
       // Once we find this function, we can stop recording.