[llvm] [Analysis][SVE] Improve cost model for some extending masked loads (PR #65957)

[David Sherwood via llvm-commits]

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@@ -2461,6 +2461,34 @@ InstructionCost AArch64TTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst,
             FP16Tbl, ISD, DstTy.getSimpleVT(), SrcTy.getSimpleVT()))
       return AdjustCost(Entry->Cost);
 
+  if ((ISD == ISD::ZERO_EXTEND || ISD == ISD::SIGN_EXTEND) &&
+      CCH == TTI::CastContextHint::Masked && ST->hasSVEorSME() &&
+      !TLI->isTypeLegal(SrcTy) && !TLI->isTypeLegal(DstTy)) {
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david-arm wrote:

That's a good question @dtemirbulatov! For non-load extends the context hint (CCH) will be TTI::CastContextHint::None, whereas I am checking for TTI::CastContextHint::Masked. That means the new code I've added only applies when we are extending a masked load.

https://github.com/llvm/llvm-project/pull/65957