diff --git a/rocket/src/main/scala/btb.scala b/rocket/src/main/scala/btb.scala index 7dfd15a2..644b02ee 100644 --- a/rocket/src/main/scala/btb.scala +++ b/rocket/src/main/scala/btb.scala @@ -47,17 +47,16 @@ class BHTResp extends Bundle with BTBParameters { class BHT(nbht: Int) { val nbhtbits = log2Up(nbht) - def get(enable: Bool, addr: UInt, btb_hit: Bool): BHTResp = { + def get(addr: UInt): BHTResp = { val res = new BHTResp val index = addr(nbhtbits+1,2) ^ history - res.history := history res.value := table(index) - val taken = res.value(0) && btb_hit - when (enable) { - history := Cat(taken, history(nbhtbits-1,1)) - } + res.history := history res } + def updateSpeculativeHistory(taken: Bool): Unit = { + history := Cat(taken, history(nbhtbits-1,1)) + } def update(addr: UInt, d: BHTResp, taken: Bool, mispredict: Bool): Unit = { val index = addr(nbhtbits+1,2) ^ d.history table(index) := Cat(taken, (d.value(1) & d.value(0)) | ((d.value(1) | d.value(0)) & taken)) @@ -92,9 +91,10 @@ class BTBResp extends Bundle with BTBParameters { // fully-associative branch target buffer class BTB extends Module with BTBParameters { val io = new Bundle { - val req = Valid(UInt(INPUT, vaddrBits)).flip + val req = UInt(INPUT, vaddrBits) val resp = Valid(new BTBResp) val update = Valid(new BTBUpdate).flip + val decode = Valid(new Bundle{val taken = Bool()}).flip val invalidate = Bool(INPUT) } @@ -124,10 +124,10 @@ class BTB extends Module with BTBParameters { } val update = Pipe(io.update) - val update_target = io.req.bits + val update_target = io.req - val pageHit = pageMatch(io.req.bits) - val hits = tagMatch(io.req.bits, pageHit) + val pageHit = pageMatch(io.req) + val hits = tagMatch(io.req, pageHit) val updatePageHit = pageMatch(update.bits.pc) val updateHits = tagMatch(update.bits.pc, updatePageHit) @@ -168,7 +168,7 @@ class BTB extends Module with BTBParameters { idxValid(waddr) := updateValid when (updateTarget) { - assert(io.req.bits === update.bits.target, "BTB request != I$ target") + assert(io.req === update.bits.target, "BTB request != I$ target") idxs(waddr) := update.bits.pc tgts(waddr) := update_target idxPages(waddr) := idxPageUpdate @@ -204,7 +204,10 @@ class BTB extends Module with BTBParameters { if (nBHT > 0) { val bht = new BHT(nBHT) - val res = bht.get(io.req.valid, io.req.bits, hits.orR) + val res = bht.get(io.req) + when (io.decode.valid) { + bht.updateSpeculativeHistory(io.decode.bits.taken) + } when (update.valid && !update.bits.isJump) { bht.update(update.bits.pc, update.bits.prediction.bits.bht, update.bits.taken, update.bits.incorrectTarget) } diff --git a/rocket/src/main/scala/icache.scala b/rocket/src/main/scala/icache.scala index da1f4c85..4119683d 100644 --- a/rocket/src/main/scala/icache.scala +++ b/rocket/src/main/scala/icache.scala @@ -5,6 +5,7 @@ package rocket import Chisel._ import uncore._ import Util._ +import Instructions._ case object NITLBEntries extends Field[Int] case object ECCCode extends Field[Option[Code]] @@ -44,7 +45,7 @@ class Frontend extends FrontendModule val cpu = new CPUFrontendIO().flip val mem = new UncachedTileLinkIO } - + val btb = Module(new BTB) val icache = Module(new ICache) val tlb = Module(new TLB(params(NITLBEntries))) @@ -85,10 +86,12 @@ class Frontend extends FrontendModule s2_valid := Bool(false) } - btb.io.req.valid := io.cpu.resp.fire() - btb.io.req.bits := s1_pc & SInt(-coreInstBytes) + btb.io.req := s1_pc & SInt(-coreInstBytes) btb.io.update := io.cpu.btb_update btb.io.invalidate := io.cpu.invalidate || io.cpu.ptw.invalidate + btb.io.decode.valid := io.cpu.resp.valid && DecodeIsBr(io.cpu.resp.bits.data) + btb.io.decode.bits.taken := Reg(next=btb.io.resp.bits.taken) + tlb.io.ptw <> io.cpu.ptw tlb.io.req.valid := !stall && !icmiss @@ -285,3 +288,21 @@ class ICache extends FrontendModule } } } + +object DecodeIsBr { + def apply(inst: Bits): Bool = { + val signal = DecodeLogic(inst.toUInt, List(N), + Array(//JAL -> List(Y), + //JALR -> List(Y), + BEQ -> List(Y), + BNE -> List(Y), + BGE -> List(Y), + BGEU -> List(Y), + BLT -> List(Y), + BLTU -> List(Y))) + + val (is_br: Bool) :: Nil = signal + is_br + } +} +