[llvm] [MemProf] Attach value profile metadata to the IR using CalleeGuids. (PR #141164)

[Teresa Johnson via llvm-commits]

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@@ -1031,15 +1072,32 @@ readMemprof(Module &M, Function &F, IndexedInstrProfReader *MemProfReader,
   // Build maps of the location hash to all profile data with that leaf location
   // (allocation info and the callsites).
   std::map<uint64_t, std::set<const AllocationInfo *>> LocHashToAllocInfo;
-  // A hash function for std::unordered_set<ArrayRef<Frame>> to work.
-  struct CallStackHash {
-    size_t operator()(ArrayRef<Frame> CS) const {
-      return computeFullStackId(CS);
+
+  // Helper struct for maintaining refs to callsite data. As an alternative we
+  // could store a pointer to the CallSiteInfo struct but we also need the frame
+  // index. Using ArrayRefs instead makes it a little easier to read.
+  struct CallSiteEntry {
+    // Subset of frames for the corresponding CallSiteInfo.
+    ArrayRef<Frame> Frames;
+    // Potential targets for indirect calls.
+    ArrayRef<GlobalValue::GUID> CalleeGuids;
+
+    // Only compare Frame contents.
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teresajohnson wrote:

Maybe comment why you aren't using ArrayRef operator==. I guess that does elementwise equality and here you are looking for the underlying pointer being the same?

https://github.com/llvm/llvm-project/pull/141164