riscv/rocket-chip
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Remove unnecessary muxes in RV32 MulDiv

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This commit is contained in:
Andrew Waterman 2016-05-25 14:27:02 -07:00
parent 9aa724706e
commit 5442b89664
1 changed files with 9 additions and 6 deletions
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15
rocket/src/main/scala/multiplier.scala
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@ -58,13 +58,16 @@ class MulDiv(
FN_MULHU -> List(Y, Y, N, N),
FN_MULHSU -> List(Y, Y, Y, N))).map(_ toBool)
def sext(x: Bits, signed: Bool) = {
val sign = signed && Mux(io.req.bits.dw === DW_64, x(w-1), x(w/2-1))
val hi = Mux(io.req.bits.dw === DW_64, x(w-1,w/2), Fill(w/2, sign))
require(w == 32 || w == 64)
def halfWidth(req: MultiplierReq) = Bool(w > 32) && req.dw === DW_32
def sext(x: Bits, halfW: Bool, signed: Bool) = {
val sign = signed && Mux(halfW, x(w/2-1), x(w-1))
val hi = Mux(halfW, Fill(w/2, sign), x(w-1,w/2))
(Cat(hi, x(w/2-1,0)), sign)
}
val (lhs_in, lhs_sign) = sext(io.req.bits.in1, lhsSigned)
val (rhs_in, rhs_sign) = sext(io.req.bits.in2, rhsSigned)
val (lhs_in, lhs_sign) = sext(io.req.bits.in1, halfWidth(io.req.bits), lhsSigned)
val (rhs_in, rhs_sign) = sext(io.req.bits.in2, halfWidth(io.req.bits), rhsSigned)
val subtractor = remainder(2*w,w) - divisor(w,0)
val less = subtractor(w)
@ -143,7 +146,7 @@ class MulDiv(
}
io.resp.bits := req
io.resp.bits.data := Mux(req.dw === DW_32, Cat(Fill(w/2, remainder(w/2-1)), remainder(w/2-1,0)), remainder(w-1,0))
io.resp.bits.data := Mux(halfWidth(req), Cat(Fill(w/2, remainder(w/2-1)), remainder(w/2-1,0)), remainder(w-1,0))
io.resp.valid := state === s_done
io.req.ready := state === s_ready
}