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

[Luke Lau via llvm-commits]

================
@@ -7197,6 +7199,48 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
       return N1.getOperand(1);
     break;
   }
+  case ISD::MCOMPRESS: {
+    EVT VecVT = N1.getValueType();
+    EVT MaskVT = N2.getValueType();
+    (void)MaskVT;
----------------
lukel97 wrote:

Nit you can use maybe_unused instead to prevent warnings
```suggestion
    [[maybe_unused]] EVT MaskVT = N2.getValueType();
```

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