[llvm] [LV] Vectorize histogram operations (PR #99851)

[Florian Hahn via llvm-commits]

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@@ -390,6 +402,22 @@ class LoopVectorizationLegality {
   unsigned getNumStores() const { return LAI->getNumStores(); }
   unsigned getNumLoads() const { return LAI->getNumLoads(); }
 
+  /// Returns a HistogramInfo* for the given instruction if it was determined
+  /// to be part of a load -> update -> store sequence where multiple lanes
+  /// may be working on the same memory address.
+  std::optional<const HistogramInfo *> getHistogramInfo(Instruction *I) const {
+    for (const HistogramInfo &HGram : Histograms)
+      if (HGram.Load == I || HGram.Update == I || HGram.Store == I)
+        return &HGram;
+
+    return std::nullopt;
+  }
+
+  /// Returns a list of all known histogram operations in the loop.
+  const SmallVectorImpl<HistogramInfo> &getHistograms() const {
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fhahn wrote:

looking at the users of this function, might be cleared to have `hasHistograms()` instead?

https://github.com/llvm/llvm-project/pull/99851