riscv/rocket-chip
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Reduce fanout on critical I$ miss signal

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Andrew Waterman 2017-06-02 14:52:52 -07:00 committed by Wesley W. Terpstra
parent 27b143013f
commit 16ecbdd5b2
1 changed files with 14 additions and 31 deletions
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45
src/main/scala/rocket/ICache.scala
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@ -108,27 +108,24 @@ class ICacheModule(outer: ICache) extends LazyModuleImp(outer)
val s2_slaveValid = RegNext(s1_slaveValid, false.B) val s2_slaveValid = RegNext(s1_slaveValid, false.B)
val s3_slaveValid = RegNext(false.B) val s3_slaveValid = RegNext(false.B)
val s_ready :: s_request :: s_refill :: Nil = Enum(UInt(), 3) val s1_valid = Reg(init=Bool(false))
val state = Reg(init=s_ready) val s1_tag_hit = Wire(Vec(nWays, Bool()))
val invalidated = Reg(Bool()) val s1_hit = s1_tag_hit.reduce(_||_) || Mux(s1_slaveValid, true.B, addrMaybeInScratchpad(io.s1_paddr))
val s2_valid = RegNext(s1_valid && !io.s1_kill, Bool(false))
val s2_hit = RegNext(s1_hit)
val refill_addr = Reg(UInt(width = paddrBits)) val invalidated = Reg(Bool())
val refill_valid = RegInit(false.B)
val s2_miss = s2_valid && !s2_hit && !io.s2_kill && !RegNext(refill_valid)
val refill_addr = RegEnable(io.s1_paddr, s1_valid && !(refill_valid || s2_miss))
val refill_tag = refill_addr(tagBits+untagBits-1,untagBits) val refill_tag = refill_addr(tagBits+untagBits-1,untagBits)
val refill_idx = refill_addr(untagBits-1,blockOffBits) val refill_idx = refill_addr(untagBits-1,blockOffBits)
val s1_tag_hit = Wire(Vec(nWays, Bool()))
val s1_any_tag_hit = s1_tag_hit.reduce(_||_) || Mux(s1_slaveValid, true.B, addrMaybeInScratchpad(io.s1_paddr))
val s1_valid = Reg(init=Bool(false))
val s1_hit = s1_valid && s1_any_tag_hit
val s1_miss = s1_valid && state === s_ready && !s1_any_tag_hit
io.req.ready := !(tl_out.d.fire() || s0_slaveValid || s3_slaveValid) io.req.ready := !(tl_out.d.fire() || s0_slaveValid || s3_slaveValid)
val s0_valid = io.req.fire() val s0_valid = io.req.fire()
val s0_vaddr = io.req.bits.addr val s0_vaddr = io.req.bits.addr
s1_valid := s0_valid s1_valid := s0_valid
when (s1_miss) { refill_addr := io.s1_paddr }
val (_, _, refill_done, refill_cnt) = edge_out.count(tl_out.d) val (_, _, refill_done, refill_cnt) = edge_out.count(tl_out.d)
tl_out.d.ready := !s3_slaveValid tl_out.d.ready := !s3_slaveValid
require (edge_out.manager.minLatency > 0) require (edge_out.manager.minLatency > 0)
@ -213,11 +210,9 @@ class ICacheModule(outer: ICache) extends LazyModuleImp(outer)
require(dECC.isInstanceOf[uncore.util.IdentityCode]) require(dECC.isInstanceOf[uncore.util.IdentityCode])
require(outer.icacheParams.itimAddr.isEmpty) require(outer.icacheParams.itimAddr.isEmpty)
io.resp.bits := Mux1H(s1_tag_hit, s1_dout) io.resp.bits := Mux1H(s1_tag_hit, s1_dout)
io.resp.valid := s1_hit io.resp.valid := s1_valid && s1_hit
case 2 => case 2 =>
val s2_valid = RegNext(s1_valid && !io.s1_kill, Bool(false))
val s2_hit = RegNext(s1_hit)
val s2_tag_hit = RegEnable(s1_tag_hit, s1_valid || s1_slaveValid) val s2_tag_hit = RegEnable(s1_tag_hit, s1_valid || s1_slaveValid)
val s2_dout = RegEnable(s1_dout, s1_valid || s1_slaveValid) val s2_dout = RegEnable(s1_dout, s1_valid || s1_slaveValid)
val s2_way_mux = Mux1H(s2_tag_hit, s2_dout) val s2_way_mux = Mux1H(s2_tag_hit, s2_dout)
@ -279,7 +274,7 @@ class ICacheModule(outer: ICache) extends LazyModuleImp(outer)
tl.e.ready := true tl.e.ready := true
} }
} }
tl_out.a.valid := state === s_request && !io.s2_kill tl_out.a.valid := s2_miss && !refill_valid
tl_out.a.bits := edge_out.Get( tl_out.a.bits := edge_out.Get(
fromSource = UInt(0), fromSource = UInt(0),
toAddress = (refill_addr >> blockOffBits) << blockOffBits, toAddress = (refill_addr >> blockOffBits) << blockOffBits,
@ -289,19 +284,7 @@ class ICacheModule(outer: ICache) extends LazyModuleImp(outer)
tl_out.e.valid := Bool(false) tl_out.e.valid := Bool(false)
assert(!(tl_out.a.valid && addrMaybeInScratchpad(tl_out.a.bits.address))) assert(!(tl_out.a.valid && addrMaybeInScratchpad(tl_out.a.bits.address)))
// control state machine when (!refill_valid) { invalidated := false.B }
switch (state) { when (tl_out.a.fire()) { refill_valid := true.B }
is (s_ready) { when (refill_done) { refill_valid := false.B}
when (s1_miss && !io.s1_kill) { state := s_request }
invalidated := Bool(false)
}
is (s_request) {
when (tl_out.a.ready) { state := s_refill }
when (io.s2_kill) { state := s_ready }
}
}
when (refill_done) {
assert(state === s_refill)
state := s_ready
}
} }