bypass stores to subsequent loads
since we handle subword stores as RMW operations, this occurs frequently
This commit is contained in:
Andrew Waterman
parent
395e4e3dd6
commit
30038bda8a
@ -110,7 +110,7 @@ class Core(implicit conf: RocketConfiguration) extends Component
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vu.io.xcpt.hold := ctrl.io.vec_iface.hold
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// hooking up vector memory interface
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dmem(2).req.bits.data := Reg(StoreGen(vu.io.dmem_req.bits.typ, Bits(0), vu.io.dmem_req.bits.data).data)
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dmem(2).req.bits.data := RegEn(StoreGen(vu.io.dmem_req.bits).data, vu.io.dmem_req.valid && isWrite(vu.io.dmem_req.bits.cmd))
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dmem(2).req <> vu.io.dmem_req
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dmem(2).resp <> vu.io.dmem_resp
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@ -47,7 +47,14 @@ class RandomReplacement(implicit conf: DCacheConfig) extends ReplacementPolicy
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def hit = {}
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}
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case class StoreGen(typ: Bits, addr: Bits, dat: Bits)
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object StoreGen
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{
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def apply(r: HellaCacheReq) = new StoreGen(r.typ, r.addr, r.data)
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def apply(r: hwacha.io_dmem_req_bundle) = new StoreGen(r.typ, r.addr, r.data)
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def apply(typ: Bits, addr: Bits, data: Bits = Bits(0)) = new StoreGen(typ, addr, data)
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}
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class StoreGen(typ: Bits, addr: Bits, dat: Bits)
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{
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val byte = typ === MT_B || typ === MT_BU
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val half = typ === MT_H || typ === MT_HU
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@ -64,7 +71,7 @@ case class StoreGen(typ: Bits, addr: Bits, dat: Bits)
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dat)))
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}
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case class LoadGen(typ: Bits, addr: Bits, dat: Bits)
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class LoadGen(typ: Bits, addr: Bits, dat: Bits)
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{
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val t = StoreGen(typ, addr, dat)
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val sign = typ === MT_B || typ === MT_H || typ === MT_W || typ === MT_D
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@ -269,23 +276,7 @@ class MSHR(id: Int)(implicit conf: DCacheConfig) extends Component {
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io.replay.bits.phys := Bool(true)
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io.replay.bits.addr := Cat(io.tag, req_idx, rpq.io.deq.bits.addr(conf.offbits-1,0)).toUFix
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// don't issue back-to-back replays with store->load dependence
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val r1_replay_valid = Reg(rpq.io.deq.fire())
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val r2_replay_valid = Reg(r1_replay_valid)
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val r3_replay_valid = Reg(r2_replay_valid)
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val r1_replay = RegEn(rpq.io.deq.bits, rpq.io.deq.fire())
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val r2_replay = RegEn(r1_replay, r1_replay_valid)
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val r3_replay = RegEn(r2_replay, r2_replay_valid)
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def offsetMatch(dst: HellaCacheReq, src: HellaCacheReq) = {
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def mask(x: HellaCacheReq) = StoreGen(x.typ, x.addr, Bits(0)).mask
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// TODO: this is overly restrictive
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dst.addr(conf.offbits-1,conf.wordoffbits) === src.addr(conf.offbits-1,conf.wordoffbits)
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// && (mask(dst) & mask(src)).orR
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}
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when (r1_replay_valid && offsetMatch(io.replay.bits, r1_replay) ||
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r2_replay_valid && offsetMatch(io.replay.bits, r2_replay) ||
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r3_replay_valid && offsetMatch(io.replay.bits, r3_replay) ||
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!io.meta_req.ready) {
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when (!io.meta_req.ready) {
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rpq.io.deq.ready := Bool(false)
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io.replay.bits.cmd := M_FENCE // NOP
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}
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@ -616,7 +607,6 @@ class DataArray(implicit conf: DCacheConfig) extends Component {
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class AMOALU(implicit conf: DCacheConfig) extends Component {
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val io = new Bundle {
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val lhs_raw = Bits(INPUT, conf.databits)
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val addr = Bits(INPUT, conf.offbits)
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val cmd = Bits(INPUT, 4)
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val typ = Bits(INPUT, 3)
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@ -627,28 +617,31 @@ class AMOALU(implicit conf: DCacheConfig) extends Component {
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require(conf.databits == 64)
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val sgned = (io.cmd === M_XA_MIN) || (io.cmd === M_XA_MAX)
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val minmax = (io.cmd === M_XA_MIN) || (io.cmd === M_XA_MINU) || (io.cmd === M_XA_MAX) || (io.cmd === M_XA_MAXU)
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val min = (io.cmd === M_XA_MIN) || (io.cmd === M_XA_MINU)
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val word = (io.typ === MT_W) || (io.typ === MT_WU)
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val sgned = io.cmd === M_XA_MIN || io.cmd === M_XA_MAX
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val max = io.cmd === M_XA_MAX || io.cmd === M_XA_MAXU
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val min = io.cmd === M_XA_MIN || io.cmd === M_XA_MINU
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val word = io.typ === MT_W || io.typ === MT_WU || io.typ === MT_B || io.typ === MT_BU
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val adder_out = io.lhs + io.rhs
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val mask = Fix(-1,64) ^ ((word & io.addr(2)) << 31)
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val adder_out = (io.lhs & mask) + (io.rhs & mask)
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val cmp_lhs = Mux(word, io.lhs(31), io.lhs(63))
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val cmp_rhs = Mux(word, io.rhs(31), io.rhs(63))
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val cmp_diff = Mux(word, io.lhs(31,0) < io.rhs(31,0), io.lhs < io.rhs)
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val less = Mux(cmp_lhs === cmp_rhs, cmp_diff, Mux(sgned, cmp_lhs, cmp_rhs))
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val cmp_out = Mux(min === less, io.lhs, io.rhs)
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val cmp_lhs = Mux(word && !io.addr(2), io.lhs(31), io.lhs(63))
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val cmp_rhs = Mux(word && !io.addr(2), io.rhs(31), io.rhs(63))
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val lt_lo = io.lhs(31,0) < io.rhs(31,0)
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val lt_hi = io.lhs(63,32) < io.rhs(63,32)
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val eq_hi = io.lhs(63,32) === io.rhs(63,32)
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val lt = Mux(word, Mux(io.addr(2), lt_hi, lt_lo), lt_hi || eq_hi && lt_lo)
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val less = Mux(cmp_lhs === cmp_rhs, lt, Mux(sgned, cmp_lhs, cmp_rhs))
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val out = Mux(io.cmd === M_XA_ADD, adder_out,
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Mux(io.cmd === M_XA_AND, io.lhs & io.rhs,
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Mux(io.cmd === M_XA_OR, io.lhs | io.rhs,
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Mux(minmax, cmp_out,
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val out = Mux(io.cmd === M_XA_ADD, adder_out,
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Mux(io.cmd === M_XA_AND, io.lhs & io.rhs,
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Mux(io.cmd === M_XA_OR, io.lhs | io.rhs,
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Mux(Mux(less, min, max), io.lhs,
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io.rhs))))
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val wdata = Mux(word, Cat(out(31,0), out(31,0)), out)
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val wmask = FillInterleaved(8, StoreGen(io.typ, io.addr, Bits(0)).mask)
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io.out := wmask & wdata | ~wmask & io.lhs_raw
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val wmask = FillInterleaved(8, StoreGen(io.typ, io.addr).mask)
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io.out := wmask & wdata | ~wmask & io.lhs
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}
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class HellaCacheReq(implicit conf: DCacheConfig) extends Bundle {
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@ -712,15 +705,19 @@ class HellaCache(implicit conf: DCacheConfig) extends Component {
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io.cpu.req.ready := Bool(true)
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val s1_valid = Reg(io.cpu.req.fire(), resetVal = Bool(false))
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val s1_req = Reg{io.cpu.req.bits.clone}
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val s1_valid_masked = s1_valid && !io.cpu.req.bits.kill
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val s1_replay = Reg(resetVal = Bool(false))
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val s1_req = Reg{io.cpu.req.bits.clone}
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val s2_req = Reg{io.cpu.req.bits.clone}
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val s1_store_bypass = Bool()
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val s2_valid = Reg(s1_valid_masked, resetVal = Bool(false))
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val s2_req = Reg{io.cpu.req.bits.clone}
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val s2_replay = Reg(s1_replay, resetVal = Bool(false))
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val s2_valid_masked = Bool()
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val s2_nack_hit = Bool()
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val s2_store_bypass = Reg{Bool()}
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val s2_store_bypass_data = Reg{Bits(width = conf.databits)}
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val s2_store_bypass_mask = Reg{Bits(width = conf.databytes)}
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val s3_valid = Reg(resetVal = Bool(false))
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val s3_req = Reg{io.cpu.req.bits.clone}
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@ -763,6 +760,7 @@ class HellaCache(implicit conf: DCacheConfig) extends Component {
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s2_req.typ := s1_req.typ
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s2_req.cmd := s1_req.cmd
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s2_req.tag := s1_req.tag
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s2_store_bypass := s1_store_bypass
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when (s1_write) {
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s2_req.data := Mux(s1_replay, mshr.io.replay.bits.data, io.cpu.req.bits.data)
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}
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@ -791,12 +789,20 @@ class HellaCache(implicit conf: DCacheConfig) extends Component {
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readArb.io.out <> data.io.read
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writeArb.io.out <> data.io.write
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// cpu tag check
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// tag read for new requests
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meta_arb.io.in(3).valid := io.cpu.req.valid
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meta_arb.io.in(3).bits.idx := io.cpu.req.bits.addr(indexmsb,indexlsb)
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meta_arb.io.in(3).bits.rw := Bool(false)
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meta_arb.io.in(3).bits.way_en := Fix(-1)
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when (!meta_arb.io.in(3).ready) { io.cpu.req.ready := Bool(false) }
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// data read for new requests
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readArb.io.in(2).bits.addr := io.cpu.req.bits.addr
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readArb.io.in(2).valid := io.cpu.req.valid
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readArb.io.in(2).bits.way_en := Fix(-1)
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when (!readArb.io.in(2).ready) { io.cpu.req.ready := Bool(false) }
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// tag check and way muxing
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def wayMap[T <: Data](f: Int => T)(gen: => T) = Vec((0 until conf.ways).map(i => f(i))){gen}
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val s1_tag_eq_way = wayMap((w: Int) => meta.io.resp(w).tag === (s1_addr >> conf.untagbits)){Bits()}.toBits
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val s1_hit_way = wayMap((w: Int) => s1_tag_eq_way(w) && conf.co.isHit(s1_req.cmd, meta.io.resp(w).state)){Bits()}.toBits
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@ -806,57 +812,10 @@ class HellaCache(implicit conf: DCacheConfig) extends Component {
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val s2_tag_match_way = RegEn(s1_tag_match_way, s1_clk_en)
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val s2_tag_match = s2_tag_match_way.orR
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val s2_hit = Reg(s1_hit)
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val s2_hit_state = Mux1H(s2_tag_match_way, wayMap((w: Int) => RegEn(meta.io.resp(w).state, s1_clk_en && s1_tag_eq_way(w))){Bits()})
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val s2_data = wayMap((w: Int) => RegEn(data.io.resp(w), s1_clk_en && s1_tag_eq_way(w))){Bits()}
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val data_resp_mux = Mux1H(s2_tag_match_way, s2_data)
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// writeback unit
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wb.io.req <> mshr.io.wb_req
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wb.io.meta_req <> meta_arb.io.in(2)
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wb.io.data_req <> readArb.io.in(1)
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wb.io.data_resp <> data_resp_mux
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wb.io.probe_rep_data <> io.mem.probe_rep_data
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// replacement policy
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val replacer = new RandomReplacement
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val s1_replaced_way_en = UFixToOH(replacer.way)
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val s2_replaced_way_en = UFixToOH(RegEn(replacer.way, s1_clk_en))
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val s2_repl_state = Mux1H(s2_replaced_way_en, wayMap((w: Int) => RegEn(meta.io.resp(w).state, s1_clk_en && s1_replaced_way_en(w))){Bits()})
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val s2_repl_tag = Mux1H(s2_replaced_way_en, wayMap((w: Int) => RegEn(meta.io.resp(w).tag, s1_clk_en && s1_replaced_way_en(w))){Bits()})
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val s2_hit_state = Mux1H(s2_tag_match_way, wayMap((w: Int) => RegEn(meta.io.resp(w).state, s1_clk_en && s1_tag_eq_way(w))){Bits()})
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// refill response
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val refill = conf.co.messageUpdatesDataArray(io.mem.xact_rep.bits)
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writeArb.io.in(1).valid := io.mem.xact_rep.valid && refill
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io.mem.xact_rep.ready := writeArb.io.in(1).ready || !refill
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writeArb.io.in(1).bits := mshr.io.mem_resp
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writeArb.io.in(1).bits.wmask := Fix(-1)
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writeArb.io.in(1).bits.data := io.mem.xact_rep.bits.data
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// load hits
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readArb.io.in(2).bits.addr := io.cpu.req.bits.addr
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readArb.io.in(2).valid := io.cpu.req.valid
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readArb.io.in(2).bits.way_en := Fix(-1)
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when (!readArb.io.in(2).ready) { io.cpu.req.ready := Bool(false) }
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// store/amo hits
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def idxMatch(dst: HellaCacheReq, src: HellaCacheReq) = dst.addr(indexmsb,indexlsb) === src.addr(indexmsb,indexlsb)
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def offsetMatch(dst: HellaCacheReq, src: HellaCacheReq) = {
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def mask(x: HellaCacheReq) = StoreGen(x.typ, x.addr, Bits(0)).mask
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// TODO: this is overly restrictive. need write-combining buffer.
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isWrite(src.cmd) &&
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dst.addr(indexlsb-1,offsetlsb) === src.addr(indexlsb-1,offsetlsb) &&
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((mask(dst) & mask(src)).orR || isWrite(dst.cmd))
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}
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def storeMatch(dst: HellaCacheReq, src: HellaCacheReq) = idxMatch(dst, src) && offsetMatch(dst, src)
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val p_store_match = s2_valid && storeMatch(s1_req, s2_req) ||
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s3_valid && storeMatch(s1_req, s3_req) ||
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s4_valid && storeMatch(s1_req, s4_req)
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writeArb.io.in(0).bits.addr := s3_req.addr
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writeArb.io.in(0).bits.wmask := UFix(1) << s3_req.addr(conf.ramoffbits-1,offsetlsb).toUFix
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writeArb.io.in(0).bits.data := Fill(MEM_DATA_BITS/conf.databits, s3_req.data)
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writeArb.io.in(0).valid := s3_valid
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writeArb.io.in(0).bits.way_en := s3_way
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// tag update after a store to an exclusive clean line.
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val new_hit_state = conf.co.newStateOnHit(s2_req.cmd, s2_hit_state)
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meta.io.state_req.bits.rw := Bool(true)
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@ -865,7 +824,7 @@ class HellaCache(implicit conf: DCacheConfig) extends Component {
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meta.io.state_req.bits.way_en := s2_tag_match_way
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meta.io.state_req.valid := s2_valid_masked && s2_hit && s2_hit_state != new_hit_state
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// pending store data, also used for AMO RHS
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// store/amo hits
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s3_valid := (s2_valid_masked && s2_hit || s2_replay) && isWrite(s2_req.cmd)
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val amoalu = new AMOALU
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when ((s2_valid || s2_replay) && isWrite(s2_req.cmd)) {
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@ -874,6 +833,19 @@ class HellaCache(implicit conf: DCacheConfig) extends Component {
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s3_way := s2_tag_match_way
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}
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writeArb.io.in(0).bits.addr := s3_req.addr
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writeArb.io.in(0).bits.wmask := UFix(1) << s3_req.addr(conf.ramoffbits-1,offsetlsb).toUFix
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writeArb.io.in(0).bits.data := Fill(MEM_DATA_BITS/conf.databits, s3_req.data)
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writeArb.io.in(0).valid := s3_valid
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writeArb.io.in(0).bits.way_en := s3_way
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// replacement policy
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val replacer = new RandomReplacement
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val s1_replaced_way_en = UFixToOH(replacer.way)
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val s2_replaced_way_en = UFixToOH(RegEn(replacer.way, s1_clk_en))
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val s2_repl_state = Mux1H(s2_replaced_way_en, wayMap((w: Int) => RegEn(meta.io.resp(w).state, s1_clk_en && s1_replaced_way_en(w))){Bits()})
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val s2_repl_tag = Mux1H(s2_replaced_way_en, wayMap((w: Int) => RegEn(meta.io.resp(w).tag, s1_clk_en && s1_replaced_way_en(w))){Bits()})
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// miss handling
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mshr.io.req.valid := s2_valid_masked && !s2_hit && (isPrefetch(s2_req.cmd) || isRead(s2_req.cmd) || isWrite(s2_req.cmd)) && !s2_nack_hit
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mshr.io.req.bits := s2_req
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@ -906,17 +878,45 @@ class HellaCache(implicit conf: DCacheConfig) extends Component {
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prober.io.line_state := s2_hit_state
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prober.io.meta_req <> meta_arb.io.in(1)
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// load data subword mux/sign extension.
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// subword loads are delayed by one cycle.
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val loadgen_data = data_resp_mux >> Cat(s2_req.addr(log2Up(MEM_DATA_BITS/8)-1,3), Bits(0,log2Up(conf.databits)))
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val loadgen = LoadGen(s2_req.typ, s2_req.addr, loadgen_data)
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// refills
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val refill = conf.co.messageUpdatesDataArray(io.mem.xact_rep.bits)
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writeArb.io.in(1).valid := io.mem.xact_rep.valid && refill
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io.mem.xact_rep.ready := writeArb.io.in(1).ready || !refill
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writeArb.io.in(1).bits := mshr.io.mem_resp
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writeArb.io.in(1).bits.wmask := Fix(-1)
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writeArb.io.in(1).bits.data := io.mem.xact_rep.bits.data
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// writebacks
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wb.io.req <> mshr.io.wb_req
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wb.io.meta_req <> meta_arb.io.in(2)
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wb.io.data_req <> readArb.io.in(1)
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wb.io.data_resp <> data_resp_mux
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wb.io.probe_rep_data <> io.mem.probe_rep_data
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// store->load bypassing
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val bypasses = List(
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(s2_valid_masked || s2_replay, s2_req, amoalu.io.out),
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(s3_valid, s3_req, s3_req.data),
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(s4_valid, s4_req, s4_req.data)
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).map(r => (r._1 && (s1_addr >> conf.wordoffbits === r._2.addr >> conf.wordoffbits) && isWrite(r._2.cmd), r._3, StoreGen(r._2).mask))
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s1_store_bypass := bypasses.map(_._1).reduce(_||_)
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when (s1_clk_en && s1_store_bypass) {
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s2_store_bypass_data := PriorityMux(bypasses.map(x => (x._1, x._2)))
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s2_store_bypass_mask := PriorityMux(bypasses.map(x => (x._1, x._3)))
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}
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// load data subword mux/sign extension
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val s2_data_word_prebypass = data_resp_mux >> Cat(s2_req.addr(log2Up(MEM_DATA_BITS/8)-1,3), Bits(0,log2Up(conf.databits)))
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val s2_data_word = Cat(null, (0 until conf.databytes).map(i => Mux(s2_store_bypass && s2_store_bypass_mask(i), s2_store_bypass_data, s2_data_word_prebypass)(8*(i+1)-1,8*i)).reverse:_*)
|
||||
val loadgen = new LoadGen(s2_req.typ, s2_req.addr, s2_data_word)
|
||||
|
||||
amoalu.io := s2_req
|
||||
amoalu.io.lhs_raw := loadgen_data
|
||||
amoalu.io.lhs := loadgen.word
|
||||
amoalu.io.lhs := s2_data_word
|
||||
amoalu.io.rhs := s2_req.data
|
||||
|
||||
val s1_nack = p_store_match || dtlb.io.req.valid && dtlb.io.resp.miss ||
|
||||
// nack it like it's hot
|
||||
def idxMatch(dst: HellaCacheReq, src: HellaCacheReq) = dst.addr(indexmsb,indexlsb) === src.addr(indexmsb,indexlsb)
|
||||
val s1_nack = dtlb.io.req.valid && dtlb.io.resp.miss ||
|
||||
idxMatch(s1_req, s2_req) && meta.io.state_req.valid ||
|
||||
s1_req.addr(indexmsb,indexlsb) === prober.io.meta_req.bits.idx && !prober.io.req.ready
|
||||
s2_nack_hit := Reg(s1_nack) || s2_hit && mshr.io.secondary_miss
|
||||
@ -925,7 +925,7 @@ class HellaCache(implicit conf: DCacheConfig) extends Component {
|
||||
val s2_nack = s2_nack_hit || s2_nack_miss || s2_nack_fence
|
||||
s2_valid_masked := s2_valid && !s2_nack
|
||||
|
||||
// after a nack, block until nack condition resolves (saves energy)
|
||||
// after a nack, block until nack condition resolves to save energy
|
||||
val block_fence = Reg(resetVal = Bool(false))
|
||||
block_fence := (s2_valid && s2_req.cmd === M_FENCE || block_fence) && !mshr.io.fence_rdy
|
||||
val block_miss = Reg(resetVal = Bool(false))
|
||||
|
||||
Loading…
Reference in New Issue
Block a user