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

[Florian Hahn via llvm-commits]

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@@ -30,6 +31,7 @@
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 #include "llvm/Transforms/Utils/ScalarEvolutionExpander.h"
+#include "llvm/Transforms/Vectorize/LoopVectorizationLegality.h"
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fhahn wrote:

It looks like VPHistogramRecipe only needs `Update` of `HistogramInfo` and that only for retrieving the legacy cost. Ideally we would include `VPHistogramRecipe::computeCost` in this patch, avoiding the need for accessing `Update`. 

If that isn't easily possibly, can we just store `Update` (with a comment what it is used for)?

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