[llvm] [RISCV] Support `llvm.masked.compressstore` intrinsic (PR #83457)

[Kolya Panchenko via llvm-commits]

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@@ -1609,3 +1609,10 @@ bool RISCVTTIImpl::isLSRCostLess(const TargetTransformInfo::LSRCost &C1,
                   C2.NumIVMuls, C2.NumBaseAdds,
                   C2.ScaleCost, C2.ImmCost, C2.SetupCost);
 }
+
+bool RISCVTTIImpl::isLegalMaskedCompressStore(Type *DataTy) {
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nikolaypanchenko wrote:

For RVV it's not required. The store of the compressed data is unaligned, i.e. it should be possible to use `vse8` for non-naturally aligned memory

https://github.com/llvm/llvm-project/pull/83457