riscv/rocket-chip
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simplify BTB fetchWidth=1 special case

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This commit is contained in:
Andrew Waterman 2016-07-04 23:43:25 -07:00
parent 2d325df60c
commit ebefe57036
1 changed files with 4 additions and 8 deletions
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12
rocket/src/main/scala/btb.scala
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@ -152,7 +152,7 @@ class BTB(implicit p: Parameters) extends BtbModule {
val useRAS = Reg(UInt(width = entries))
val isJump = Reg(UInt(width = entries))
val brIdx = Reg(Vec(entries, UInt(width=log2Up(fetchWidth))))
val brIdx = if (fetchWidth > 1) Reg(Vec(entries, UInt(width=log2Up(fetchWidth)))) else Seq(UInt(0))
private def page(addr: UInt) = addr >> matchBits
private def pageMatch(addr: UInt) = {
@ -214,11 +214,8 @@ class BTB(implicit p: Parameters) extends BtbModule {
val mask = UIntToOH(waddr)
useRAS := Mux(r_btb_update.bits.isReturn, useRAS | mask, useRAS & ~mask)
isJump := Mux(r_btb_update.bits.isJump, isJump | mask, isJump & ~mask)
if (fetchWidth == 1) {
brIdx(waddr) := UInt(0)
} else {
if (fetchWidth > 1)
brIdx(waddr) := r_btb_update.bits.br_pc >> log2Up(coreInstBytes)
}
require(nPages % 2 == 0)
val idxWritesEven = !idxPageUpdate(0)
@ -237,9 +234,8 @@ class BTB(implicit p: Parameters) extends BtbModule {
io.resp.bits.taken := io.resp.valid
io.resp.bits.target := Cat(Mux1H(Mux1H(hitsVec, tgtPagesOH), pages), Mux1H(hitsVec, tgts))
io.resp.bits.entry := OHToUInt(hits)
io.resp.bits.bridx := brIdx(io.resp.bits.entry)
io.resp.bits.mask := Mux(io.resp.bits.taken, Cat((UInt(1) << brIdx(io.resp.bits.entry))-1, UInt(1)).toSInt,
SInt(-1)).toUInt
io.resp.bits.bridx := Mux1H(hitsVec, brIdx)
io.resp.bits.mask := Cat((UInt(1) << ~Mux(io.resp.bits.taken, ~io.resp.bits.bridx, UInt(0)))-1, UInt(1))
if (nBHT > 0) {
val bht = new BHT(nBHT)