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Explicitly discard BTB index LSBs

This commit is contained in:
Andrew Waterman 2016-07-14 17:10:27 -07:00
parent e6aab368a4
commit da512d4230
1 changed files with 9 additions and 8 deletions
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17
rocket/src/main/scala/btb.scala
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@ -142,18 +142,18 @@ class BTB(implicit p: Parameters) extends BtbModule {
val ras_update = Valid(new RASUpdate).flip
}
val idxs = Reg(Vec(entries, UInt(width=matchBits)))
val idxs = Reg(Vec(entries, UInt(width=matchBits - log2Up(coreInstBytes))))
val idxPages = Reg(Vec(entries, UInt(width=log2Up(nPages))))
val tgts = Reg(Vec(entries, UInt(width=matchBits)))
val tgts = Reg(Vec(entries, UInt(width=matchBits - log2Up(coreInstBytes))))
val tgtPages = Reg(Vec(entries, UInt(width=log2Up(nPages))))
val pages = Reg(Vec(nPages, UInt(width=vaddrBits-matchBits)))
val pages = Reg(Vec(nPages, UInt(width=vaddrBits - matchBits)))
val pageValid = Reg(init = UInt(0, nPages))
val idxPagesOH = idxPages.map(UIntToOH(_)(nPages-1,0))
val tgtPagesOH = tgtPages.map(UIntToOH(_)(nPages-1,0))
val useRAS = Reg(UInt(width = entries))
val isJump = Reg(UInt(width = entries))
val brIdx = if (fetchWidth > 1) Reg(Vec(entries, UInt(width=log2Up(fetchWidth)))) else Seq(UInt(0))
val brIdx = Reg(Vec(entries, UInt(width=log2Up(fetchWidth))))
private def page(addr: UInt) = addr >> matchBits
private def pageMatch(addr: UInt) = {
@ -161,7 +161,7 @@ class BTB(implicit p: Parameters) extends BtbModule {
pageValid & pages.map(_ === p).toBits
}
private def tagMatch(addr: UInt, pgMatch: UInt) = {
val idxMatch = idxs.map(_ === addr(matchBits-1,0)).toBits
val idxMatch = idxs.map(_ === addr(matchBits-1, log2Up(coreInstBytes))).toBits
val idxPageMatch = idxPagesOH.map(_ & pgMatch).map(_.orR).toBits
idxMatch & idxPageMatch
}
@ -209,8 +209,9 @@ class BTB(implicit p: Parameters) extends BtbModule {
val waddr = Mux(updateHit && !resetting, updateHitAddr, nextRepl)
val mask = UIntToOH(waddr)
idxs(waddr) := Mux(resetting, Cat(r_btb_update.bits.pc >> log2Ceil(entries), nextRepl), r_btb_update.bits.pc)
tgts(waddr) := update_target
val newIdx = r_btb_update.bits.pc(matchBits-1, log2Up(coreInstBytes))
idxs(waddr) := Mux(resetting, Cat(newIdx >> log2Ceil(entries), nextRepl), newIdx)
tgts(waddr) := update_target(matchBits-1, log2Up(coreInstBytes))
idxPages(waddr) := idxPageUpdate
tgtPages(waddr) := tgtPageUpdate
useRAS := Mux(r_btb_update.bits.isReturn, useRAS | mask, useRAS & ~mask)
@ -234,7 +235,7 @@ class BTB(implicit p: Parameters) extends BtbModule {
io.resp.valid := hits.orR
io.resp.bits.taken := io.resp.valid
io.resp.bits.target := Cat(Mux1H(Mux1H(hitsVec, tgtPagesOH), pages), Mux1H(hitsVec, tgts))
io.resp.bits.target := Cat(Mux1H(Mux1H(hitsVec, tgtPagesOH), pages), Mux1H(hitsVec, tgts) << log2Up(coreInstBytes))
io.resp.bits.entry := OHToUInt(hits)
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))