[llvm] [LLVM] Add `llvm.masked.compress` intrinsic (PR #92289)

[Luke Lau via llvm-commits]

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@@ -6279,7 +6279,9 @@ SDValue SelectionDAG::FoldConstantArithmetic(unsigned Opcode, const SDLoc &DL,
   // We can't create a scalar CONCAT_VECTORS so skip it. It will break
   // for concats involving SPLAT_VECTOR. Concats of BUILD_VECTORS are handled by
   // foldCONCAT_VECTORS in getNode before this is called.
-  if (Opcode >= ISD::BUILTIN_OP_END || Opcode == ISD::CONCAT_VECTORS)
+  // MCOMPRESS is not defined for scalars. We handle constants before this call.
+  if (Opcode >= ISD::BUILTIN_OP_END || Opcode == ISD::CONCAT_VECTORS ||
+      Opcode == ISD::MCOMPRESS)
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lukel97 wrote:

How come we need to bail here for MCOMPRESS but not for other vector binary ops like VECTOR_DEINTERLEAVE etc? 

https://github.com/llvm/llvm-project/pull/92289