vector: add mask extractor

src/main/scala/xiangshan/backend/fu/vector/utils/MaskExtrator.scala

+package xiangshan.backend.fu.vector.utils
+
+import chisel3._
+import chisel3.util._
+import xiangshan.backend.fu.vector.Bundles.VSew
+
+class MaskExtractorIO(vlen: Int) extends Bundle {
+  private val numBytes = vlen / 8
+
+  val in = Input(new Bundle {
+    val mask = UInt(numBytes.W)
+    val vsew = VSew()
+  })
+  val out = Output(new Bundle {
+    val mask = UInt(numBytes.W)
+  })
+}
+
+class MaskExtractor(vlen: Int) extends Module {
+  private val numBytes = vlen / 8
+
+  val io = IO(new MaskExtractorIO(vlen))
+
+  private val mask = io.in.mask
+  private val vsew = io.in.vsew
+  private val extractedMask = Wire(UInt(vlen.W))
+
+  extractedMask := Mux1H(Seq(
+    (vsew === VSew.e8)  -> mask,
+    (vsew === VSew.e16) -> VecInit(mask.asBools.flatMap(Seq.fill(2)(_))).asUInt,
+    (vsew === VSew.e32) -> VecInit(mask.asBools.flatMap(Seq.fill(4)(_))).asUInt,
+    (vsew === VSew.e64) -> VecInit(mask.asBools.flatMap(Seq.fill(8)(_))).asUInt,
+  ))
+
+  io.out.mask := extractedMask
+}
+
+object MaskExtractor {
+  def apply(vlen: Int)(mask: UInt, vsew: UInt): UInt = {
+    val maskExtractor = Module(new MaskExtractor(vlen))
+    maskExtractor.io.in.mask := mask
+    maskExtractor.io.in.vsew := vsew
+    maskExtractor.io.out.mask
+  }
+}
+
+object VerilogMaskExtrator extends App {
+  println("Generating the MaskExtractor hardware")
+  emitVerilog(new MaskExtractor(128), Array("--full-stacktrace", "--target-dir", "build/MaskExtractor"))
+}