riscv/rocket-chip
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Don't compile BTB when nEntries=0

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This commit is contained in:
Andrew Waterman 2016-04-01 15:14:45 -07:00
parent d406dc1231
commit 4480d1e817
1 changed files with 25 additions and 17 deletions
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42
rocket/src/main/scala/frontend.scala
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@ -34,7 +34,6 @@ class Frontend(implicit p: Parameters) extends CoreModule()(p) with HasL1CachePa
val mem = new ClientUncachedTileLinkIO
}
val btb = Module(new BTB)
val icache = Module(new ICache)
val tlb = Module(new TLB)
@ -44,20 +43,19 @@ class Frontend(implicit p: Parameters) extends CoreModule()(p) with HasL1CachePa
val s2_valid = Reg(init=Bool(true))
val s2_pc = Reg(init=UInt(p(ResetVector)))
val s2_btb_resp_valid = Reg(init=Bool(false))
val s2_btb_resp_bits = Reg(btb.io.resp.bits)
val s2_btb_resp_bits = Reg(new BTBResp)
val s2_xcpt_if = Reg(init=Bool(false))
val s2_resp_valid = Wire(init=Bool(false))
val s2_resp_data = Wire(UInt(width = rowBits))
val msb = vaddrBits-1
val lsb = log2Up(fetchWidth*coreInstBytes)
val btbTarget = Cat(btb.io.resp.bits.target(msb), btb.io.resp.bits.target)
val ntpc_0 = s1_pc + UInt(coreInstBytes*fetchWidth)
val ntpc = Cat(s1_pc(msb) & ntpc_0(msb), ntpc_0(msb,lsb), Bits(0,lsb)) // unsure
val ntpc_0 = ~(~s1_pc | (coreInstBytes*fetchWidth-1)) + UInt(coreInstBytes*fetchWidth)
val ntpc = // don't increment PC into virtual address space hole
if (vaddrBitsExtended == vaddrBits) ntpc_0
else Cat(s1_pc(vaddrBits-1) & ntpc_0(vaddrBits-1), ntpc_0)
val predicted_npc = Wire(init = ntpc)
val icmiss = s2_valid && !s2_resp_valid
val predicted_npc = Mux(btb.io.resp.bits.taken, btbTarget, ntpc)
val npc = Mux(icmiss, s2_pc, predicted_npc).toUInt
val s0_same_block = !icmiss && !io.cpu.req.valid && !btb.io.resp.bits.taken && ((ntpc & rowBytes) === (s1_pc & rowBytes))
val s0_same_block = Wire(init = !icmiss && !io.cpu.req.valid && ((ntpc & rowBytes) === (s1_pc & rowBytes)))
val stall = io.cpu.resp.valid && !io.cpu.resp.ready
when (!stall) {
@ -66,8 +64,6 @@ class Frontend(implicit p: Parameters) extends CoreModule()(p) with HasL1CachePa
s2_valid := !icmiss
when (!icmiss) {
s2_pc := s1_pc
s2_btb_resp_valid := btb.io.resp.valid
when (btb.io.resp.valid) { s2_btb_resp_bits := btb.io.resp.bits }
s2_xcpt_if := tlb.io.resp.xcpt_if
}
}
@ -77,12 +73,24 @@ class Frontend(implicit p: Parameters) extends CoreModule()(p) with HasL1CachePa
s2_valid := Bool(false)
}
btb.io.req.valid := !stall && !icmiss
btb.io.req.bits.addr := s1_pc
btb.io.btb_update := io.cpu.btb_update
btb.io.bht_update := io.cpu.bht_update
btb.io.ras_update := io.cpu.ras_update
btb.io.invalidate := io.cpu.invalidate || io.ptw.invalidate
if (p(BtbKey).nEntries > 0) {
val btb = Module(new BTB)
btb.io.req.valid := false
btb.io.req.bits.addr := s1_pc
btb.io.btb_update := io.cpu.btb_update
btb.io.bht_update := io.cpu.bht_update
btb.io.ras_update := io.cpu.ras_update
btb.io.invalidate := io.cpu.invalidate || io.ptw.invalidate
when (!stall && !icmiss) {
btb.io.req.valid := true
s2_btb_resp_valid := btb.io.resp.valid
s2_btb_resp_bits := btb.io.resp.bits
}
when (btb.io.resp.bits.taken) {
predicted_npc := btb.io.resp.bits.target.sextTo(vaddrBitsExtended)
s0_same_block := Bool(false)
}
}
io.ptw <> tlb.io.ptw
tlb.io.req.valid := !stall && !icmiss