[X86] Enable v32f16 FNEG custom lowering on AVX512 targets

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -2054,6 +2054,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
       for (auto VT : { MVT::v4i32, MVT::v8i32, MVT::v2i64, MVT::v4i64 })
         setOperationAction(ISD::CTPOP, VT, Legal);
     }
+    setOperationAction(ISD::FNEG, MVT::v32f16, Custom);
     setOperationAction(ISD::FABS, MVT::v32f16, Custom);
   }