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凿子:如何对展开循环中递增的变量建模

loop-unrolling chisel counter

0

aayupov · 技术社区 · 8 年前

考虑到我的HLS背景和编码风格,我想写以下内容:

  def foo ( in : Vec[UInt] ) = {

    val out = Vec.fill(in.size) {UInt(in.size)}
    val nextInd = Wire(init = 0.U)

    in.zipWithIndex.foreach {case(val, ind) => 
      when(val === true.B) {
        out(ind) := nextInd
        nextInd := Wire(init = nextInd+1.U)
      }
    }
  }

2 回复 | 直到 8 年前

1

2

Chick Markley 8 年前

以下内容似乎更简单:

  // return is a Vec with each element equal to the sum of bits up to it's index
  def foo(inBits: Vec[Bool]): Vec[UInt] = {
    val counts = Vec(size, UInt(log2Ceil(size + 1).W))
    inBits.zipWithIndex.foldLeft(0.U) { case (lastValue, (bit, index)) =>
      counts(index) := bit + lastValue
      counts(index)
    }
    counts
  }

2

0

aayupov 8 年前

  def foo ( in : Vec[UInt] ) = {
    val vecSize = in.size
    val out = Vec.fill(vecSize) {UInt(vecSize)}

    in.zipWithIndex.foldLeft (Wire(init = 0.U)) {case(prevInd,(val, ind)) => 
      // val nextInd = Wire(init = prevInd) // this will not work due to bitwidth be not enough to hold an incremented value, so i do the following instead
      val nextInd = Wire(init = UInt(vecSize)) // here i just make sure the width is enough
      nextInd := prevInd
      when(val === true.B) {
        out(ind) := prevInd
        nextInd := Wire(init = prevInd+1.U)
      }
      nextInd
    }
  }