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iterative mul improvments

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This commit is contained in:
Dolu1990 2018-03-09 20:00:50 +01:00
parent 674ab2c594
commit 36438bd306
1 changed files with 20 additions and 9 deletions
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29
src/main/scala/vexriscv/plugin/MulDivIterativePlugin.scala
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@ -44,16 +44,22 @@ class MulDivIterativePlugin(mulUnroolFactor : Int = 1) extends Plugin[VexRiscv]{
memory plug new Area {
import memory._
val rs1 = Reg(UInt(64 bits))
val rs1 = Reg(UInt(33 bits))
val rs2 = Reg(UInt(32 bits))
val accumulator = Reg(UInt(64 bits))
val accumulator = Reg(UInt(65 bits))
val mul = new Area{
val done = rs2 === 0
assert(isPow2(mulUnroolFactor))
val counter = Counter(32 / mulUnroolFactor + 1)
val done = counter.willOverflowIfInc
when(input(IS_MUL)){
arbitration.haltItself setWhen(!done)
rs1 := rs1 |<< mulUnroolFactor
rs2 := rs2 |>> mulUnroolFactor
accumulator := ((0 until mulUnroolFactor).map(i => rs2(i) ? (rs1 |<< i) | U(0)) :+ accumulator).reduceBalancedTree(_ + _)
when(!done){
arbitration.haltItself := True
counter.increment()
rs2 := rs2 |>> mulUnroolFactor
val sumElements = ((0 until mulUnroolFactor).map(i => rs2(i) ? (rs1 << i) | U(0)) :+ (accumulator >> 32))
val sumResult = sumElements.map(_.asSInt.resize(32 + mulUnroolFactor + 1).asUInt).reduceBalancedTree(_ + _)
accumulator := (sumResult @@ accumulator(31 downto 0)) >> mulUnroolFactor
}
output(REGFILE_WRITE_DATA) := ((input(INSTRUCTION)(13 downto 12) === B"00") ? accumulator(31 downto 0) | accumulator(63 downto 32)).asBits
}
}
@ -62,10 +68,15 @@ class MulDivIterativePlugin(mulUnroolFactor : Int = 1) extends Plugin[VexRiscv]{
accumulator := 0
def twoComplement(that : Bits, enable: Bool): UInt = (Mux(enable, ~that, that).asUInt + enable.asUInt)
val rs2NeedRevert = execute.input(RS2).msb && execute.input(IS_RS2_SIGNED)
val rs1Extended = B((63 downto 32) -> (execute.input(IS_RS1_SIGNED) && execute.input(RS1).msb), (31 downto 0) -> execute.input(RS1))
rs1 := twoComplement(rs1Extended, rs2NeedRevert)
val rs1Extended = B((32 downto 32) -> (execute.input(IS_RS1_SIGNED) && execute.input(RS1).msb), (31 downto 0) -> execute.input(RS1))
rs1 := twoComplement(rs1Extended, rs2NeedRevert).resized
rs2 := twoComplement(execute.input(RS2), rs2NeedRevert)
mul.counter.clear()
}
}
}
}
// val mulEnables = rs2.subdivideIn(mulUnroolFactor bits)(counter(log2Up(32/mulUnroolFactor)-1 downto 0))