[llvm] [IA][RISCV] Recognize deinterleaved loads that could lower to strided segmented loads (PR #151612)

[Luke Lau via llvm-commits]

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@@ -3209,10 +3209,12 @@ class LLVM_ABI TargetLoweringBase {
   /// \p Shuffles is the shufflevector list to DE-interleave the loaded vector.
   /// \p Indices is the corresponding indices for each shufflevector.
   /// \p Factor is the interleave factor.
+  /// \p MaskFactor is the interleave factor that considers mask, which can
+  /// reduce the original factor.
   virtual bool lowerInterleavedLoad(Instruction *Load, Value *Mask,
                                     ArrayRef<ShuffleVectorInst *> Shuffles,
-                                    ArrayRef<unsigned> Indices,
-                                    unsigned Factor) const {
+                                    ArrayRef<unsigned> Indices, unsigned Factor,
+                                    unsigned MaskFactor) const {
     return false;
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lukel97 wrote:

Oh whoops yes, that should be multiplied by factor. 

To me MaskFactor feels like a concept internal to InterleavedAccessPass that's leaking through.

I'm not strongly opinionated about this though, just thought I'd throw the idea out there, happy to go with what you prefer. 

I guess an alternative is that we could also add a separate "lowerStridedInterleaved" TTI hook. But maybe that will lead to hook explosion again

https://github.com/llvm/llvm-project/pull/151612