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path: root/src/test/scala/chiselTests/Decoder.scala
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// See LICENSE for license details.

package chiselTests
import Chisel._
import org.scalatest._
import org.scalatest.prop._
import org.scalacheck._
import Chisel.testers.BasicTester

class Decoder(bitpats: List[String]) extends Module {
  val io = IO(new Bundle {
    val inst  = Input(UInt(32))
    val matched = Output(Bool())
  })
  io.matched := Vec(bitpats.map(BitPat(_) === io.inst)).reduce(_||_)
}

class DecoderTester(pairs: List[(String, String)]) extends BasicTester {
  val (insts, bitpats) = pairs.unzip
  val (cnt, wrap) = Counter(Bool(true), pairs.size)
  val dut = Module(new Decoder(bitpats))
  dut.io.inst := Vec(insts.map(UInt(_)))(cnt)
  when(!dut.io.matched) {
    assert(cnt === UInt(0))
    stop()
  }
  when(wrap) {
    stop()
  }
}

class DecoderSpec extends ChiselPropSpec {

  // Use a single Int to make both a specific instruction and a BitPat that will match it
  val bitpatPair = for(seed <- Arbitrary.arbitrary[Int]) yield {
    val rnd = new scala.util.Random(seed)
    val bs = seed.toBinaryString
    val bp = bs.map(if(rnd.nextBoolean) _ else "?").mkString
    ("b" + bs, "b" + bp)
  }
  private def nPairs(n: Int) = Gen.containerOfN[List, (String,String)](n,bitpatPair)

  property("BitPat wildcards should be usable in decoding") {
    forAll(nPairs(4)){ (pairs: List[(String, String)]) =>
      assertTesterPasses{ new DecoderTester(pairs) }
    }
  }
}