riscv/rocket-chip
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Add early out to multiplier

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This commit is contained in:
Andrew Waterman 2013-08-24 14:42:50 -07:00
parent 67f80ba4b2
commit daf23b8f79
1 changed files with 5 additions and 2 deletions
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7
rocket/src/main/scala/divider.scala
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@ -54,11 +54,14 @@ class MulDiv(mulUnroll: Int = 1, earlyOut: Boolean = false)(implicit conf: Rocke
val accum = mulReg(2*mulw,mulw).toSInt
val mpcand = divisor.toSInt
val prod = mplier(mulUnroll-1,0) * mpcand + accum
val nextMulReg = Cat(prod, mplier(mulw-1,mulUnroll)).toUInt
val eOut = Bool(earlyOut) && count > 0 &&
(0 until mulw/mulUnroll).map(i => i > mulw/mulUnroll-1-count || mplier((i+1)*mulUnroll-1,i*mulUnroll) === 0).reduce(_&&_)
val eOutValue = mulReg >> (mulw/mulUnroll-count)(log2Up(mulw/mulUnroll)-1,0)*mulUnroll
val nextMulReg = Mux(eOut, eOutValue, Cat(prod, mplier(mulw-1,mulUnroll)))
remainder := Cat(nextMulReg >> w, Bool(false), nextMulReg(w-1,0)).toSInt
count := count + 1
when (count === mulw/mulUnroll-1) {
when (count === mulw/mulUnroll-1 || eOut) {
state := s_done
when (AVec(FN_MULH, FN_MULHU, FN_MULHSU) contains req.fn) {
state := s_move_rem