[llvm] [CodeGen] Expand unsupported (de)interleave intrinsics (PR #207439)

[Matt Arsenault via llvm-commits]

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@@ -3301,6 +3300,13 @@ class LLVM_ABI TargetLoweringBase {
   /// Default to be the minimum interleave factor: 2.
   virtual unsigned getMaxSupportedInterleaveFactor() const { return 2; }
 
+  /// Return true if a fixed-length VECTOR_INTERLEAVE / VECTOR_DEINTERLEAVE
+  /// should be expanded to a shufflevector sequence.
+  virtual bool shouldExpandVectorInterleaveToShuffle(unsigned Factor,
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arsenm wrote:

Should try to avoid adding a new hook. And if it's really needed it should be in terms of what's supported or not, not prescribing a vague action 

https://github.com/llvm/llvm-project/pull/207439