riscv/rocket-chip
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Add early out for MUL[W] (not MULH[[S]U])

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This commit is contained in:
Andrew Waterman 2014-04-07 23:48:02 -07:00
parent 927287da34
commit 3ed8adf032
1 changed files with 8 additions and 2 deletions
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10
rocket/src/main/scala/multiplier.scala
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@ -91,10 +91,16 @@ class MulDiv(mulUnroll: Int = 1, earlyOut: Boolean = false)(implicit conf: Rocke
val mpcand = divisor.toSInt val mpcand = divisor.toSInt
val prod = mplier(mulUnroll-1,0) * mpcand + accum val prod = mplier(mulUnroll-1,0) * mpcand + accum
val nextMulReg = Cat(prod, mplier(mulw-1,mulUnroll)).toUInt val nextMulReg = Cat(prod, mplier(mulw-1,mulUnroll)).toUInt
remainder := Cat(nextMulReg >> w, Bool(false), nextMulReg(w-1,0)).toSInt
val eOutMask = (SInt(BigInt(-1) << mulw) >> (count * mulUnroll)(log2Up(mulw)-1,0))(mulw-1,0)
val eOut = Bool(earlyOut) && count != mulw/mulUnroll-1 && count != 0 &&
!isHi && (mplier & ~eOutMask) === UInt(0)
val eOutRes = (mulReg >> (mulw - count * mulUnroll)(log2Up(mulw)-1,0))
val nextMulReg1 = Cat(nextMulReg(2*mulw,mulw), Mux(eOut, eOutRes, nextMulReg)(mulw-1,0))
remainder := Cat(nextMulReg1 >> w, Bool(false), nextMulReg1(w-1,0)).toSInt
count := count + 1 count := count + 1
when (count === mulw/mulUnroll-1) { when (eOut || count === mulw/mulUnroll-1) {
state := Mux(isHi, s_move_rem, s_done) state := Mux(isHi, s_move_rem, s_done)
} }
} }