riscv/rocket-chip
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don't refetch from I$ if on same 16B block

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This commit is contained in:
Andrew Waterman 2012-10-11 16:54:28 -07:00
parent b955985b38
commit 5821900329
1 changed files with 14 additions and 8 deletions
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22
rocket/src/main/scala/icache.scala
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@ -5,6 +5,7 @@ import Node._;
import Constants._;
import scala.math._;
import uncore._
import Util._
case class ICacheConfig(co: CoherencePolicyWithUncached, sets: Int, assoc: Int, parity: Boolean = false)
{
@ -62,6 +63,7 @@ class Frontend(c: ICacheConfig) extends Component
val tlb = new TLB(ITLB_ENTRIES)
val s1_pc = Reg() { UFix() }
val s1_same_block = Reg() { Bool() }
val s2_valid = Reg(resetVal = Bool(true))
val s2_pc = Reg(resetVal = UFix(START_ADDR))
val s2_btb_hit = Reg(resetVal = Bool(false))
@ -71,10 +73,13 @@ class Frontend(c: ICacheConfig) extends Component
val pcp4_0 = s1_pc + UFix(c.ibytes)
val pcp4 = Cat(s1_pc(VADDR_BITS-1) & pcp4_0(VADDR_BITS-1), pcp4_0(VADDR_BITS-1,0))
val icmiss = s2_valid && !icache.io.resp.valid
val npc = Mux(icmiss, s2_pc, Mux(btb.io.hit, btbTarget, pcp4)).toUFix
val predicted_npc = Mux(btb.io.hit, btbTarget, pcp4)
val npc = Mux(icmiss, s2_pc, predicted_npc).toUFix
val s0_same_block = !icmiss && !io.cpu.req.valid && (predicted_npc >> log2Up(c.databits/8)) === (s1_pc >> log2Up(c.databits/8))
val stall = !io.cpu.resp.ready
val stall = io.cpu.resp.valid && !io.cpu.resp.ready
when (!stall) {
s1_same_block := s0_same_block && !tlb.io.resp.miss
s1_pc := npc
s2_valid := !icmiss
s2_pc := s1_pc
@ -82,6 +87,7 @@ class Frontend(c: ICacheConfig) extends Component
s2_xcpt_if := tlb.io.resp.xcpt_if
}
when (io.cpu.req.valid) {
s1_same_block := Bool(false)
s1_pc := io.cpu.req.bits.pc
s2_valid := Bool(false)
}
@ -102,16 +108,16 @@ class Frontend(c: ICacheConfig) extends Component
tlb.io.req.bits.instruction := Bool(true)
icache.io.mem <> io.mem
icache.io.req.valid := !stall
icache.io.req.valid := !stall && !s0_same_block
icache.io.req.bits.idx := Mux(io.cpu.req.valid, io.cpu.req.bits.pc, npc)
icache.io.req.bits.invalidate := io.cpu.req.bits.invalidate
icache.io.req.bits.ppn := tlb.io.resp.ppn
icache.io.req.bits.kill := io.cpu.req.valid || tlb.io.resp.miss
icache.io.resp.ready := io.cpu.resp.ready
icache.io.resp.ready := !stall && !s1_same_block
io.cpu.resp.valid := s2_valid && (s2_xcpt_if || icache.io.resp.valid)
io.cpu.resp.bits.pc := s2_pc
io.cpu.resp.bits.data := icache.io.resp.bits.data
io.cpu.resp.bits.data := icache.io.resp.bits.datablock >> (s2_pc(log2Up(c.databits/8)-1,log2Up(c.ibytes)) << log2Up(c.ibytes*8))
io.cpu.resp.bits.taken := s2_btb_hit
io.cpu.resp.bits.xcpt_ma := s2_pc(log2Up(c.ibytes)-1,0) != UFix(0)
io.cpu.resp.bits.xcpt_if := s2_xcpt_if
@ -141,6 +147,7 @@ class ICache(c: ICacheConfig) extends Component
val s2_valid = Reg(resetVal = Bool(false))
val s2_addr = Reg { UFix(width = PADDR_BITS) }
val s2_any_tag_hit = Bool()
val s1_valid = Reg(resetVal = Bool(false))
val s1_pgoff = Reg() { UFix(width = PGIDX_BITS) }
@ -153,7 +160,7 @@ class ICache(c: ICacheConfig) extends Component
s1_pgoff := s0_pgoff
}
s2_valid := s1_valid && rdy && !io.req.bits.kill || stall
s2_valid := s1_valid && rdy && !io.req.bits.kill || io.resp.valid && stall
when (s1_valid && rdy && !stall) {
s2_addr := Cat(io.req.bits.ppn, s1_pgoff).toUFix
}
@ -161,7 +168,6 @@ class ICache(c: ICacheConfig) extends Component
val s2_tag = s2_addr(c.tagbits+c.untagbits-1,c.untagbits)
val s2_idx = s2_addr(c.untagbits-1,c.offbits)
val s2_offset = s2_addr(c.offbits-1,0)
val s2_any_tag_hit = Bool()
val s2_hit = s2_valid && s2_any_tag_hit
val s2_miss = s2_valid && !s2_any_tag_hit
rdy := state === s_ready && !s2_miss
@ -220,7 +226,7 @@ class ICache(c: ICacheConfig) extends Component
when (s1_valid && rdy && !stall) { s2_dout(i) := s1_dout }
s2_data_disparity(i) := s2_dout(i).xorR
}
val s2_dout_word = s2_dout.map(x => (x >> Cat(s2_offset(log2Up(c.databits/8)-1,log2Up(c.ibytes)), Bits(0,log2Up(c.ibytes*8))))(c.ibytes*8-1,0))
val s2_dout_word = s2_dout.map(x => (x >> (s2_offset(log2Up(c.databits/8)-1,log2Up(c.ibytes)) << log2Up(c.ibytes*8)))(c.ibytes*8-1,0))
io.resp.bits.data := Mux1H(s2_tag_hit, s2_dout_word)
io.resp.bits.datablock := Mux1H(s2_tag_hit, s2_dout)