[llvm] [SLP]Improved reduction cost/codegen (PR #118293)

[Alexey Bataev via llvm-commits]

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@@ -1613,6 +1613,11 @@ class TargetTransformInfo {
   /// split during legalization. Zero is returned when the answer is unknown.
   unsigned getNumberOfParts(Type *Tp) const;
 
+  /// \return true if \p Tp represents a type, fully occupying whole register,
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alexey-bataev wrote:

Added `(up to known minimum length)`. Is this enough?

https://github.com/llvm/llvm-project/pull/118293