Support non-power-of-2 BTBs; prefer invalid entries
This commit is contained in:
parent
daf23b8f79
commit
3895b75a56
@ -23,27 +23,29 @@ class rocketDpathBTB(entries: Int) extends Module
|
||||
{
|
||||
val io = new DpathBTBIO
|
||||
|
||||
val repl_way = LFSR16(io.wen)(log2Up(entries)-1,0) // TODO: pseudo-LRU
|
||||
|
||||
var hit_reduction = Bool(false)
|
||||
val hit = Bool()
|
||||
val update = Bool()
|
||||
var update_reduction = Bool(false)
|
||||
val valid = Vec.fill(entries){Reg(init=Bool(false))}
|
||||
val hits = Vec.fill(entries){Bool()}
|
||||
val updates = Vec.fill(entries){Bool()}
|
||||
val targets = Vec.fill(entries){Reg(UInt())}
|
||||
val anyUpdate = updates.toBits.orR
|
||||
|
||||
val random_way = Random(entries, io.wen)
|
||||
val invalid_way = valid.indexWhere((x: Bool) => !x)
|
||||
val repl_way = Mux(valid.contains(Bool(false)), invalid_way, random_way)
|
||||
|
||||
for (i <- 0 until entries) {
|
||||
val tag = Reg(UInt())
|
||||
val valid = Reg(init=Bool(false))
|
||||
hits(i) := valid && tag === io.current_pc
|
||||
updates(i) := valid && tag === io.correct_pc
|
||||
hits(i) := valid(i) && tag === io.current_pc
|
||||
updates(i) := valid(i) && tag === io.correct_pc
|
||||
|
||||
when (io.wen && (updates(i) || !anyUpdate && UInt(i) === repl_way)) {
|
||||
valid := Bool(false)
|
||||
valid(i) := Bool(false)
|
||||
when (!io.clr) {
|
||||
valid := Bool(true)
|
||||
valid(i) := Bool(true)
|
||||
tag := io.correct_pc
|
||||
targets(i) := io.correct_target
|
||||
}
|
||||
|
@ -130,3 +130,21 @@ case class WideCounter(width: Int, inc: Bool = Bool(true))
|
||||
if (isWide) large := (if (w < smallWidth) UInt(0) else x(w.min(width)-1,smallWidth))
|
||||
}
|
||||
}
|
||||
|
||||
object Random
|
||||
{
|
||||
def apply(mod: Int, inc: Bool = Bool(true)): UInt = {
|
||||
if (isPow2(mod)) {
|
||||
require(mod <= 65536)
|
||||
LFSR16(inc)(log2Up(mod)-1,0).toUInt
|
||||
} else {
|
||||
val max = 1 << log2Up(mod*8)
|
||||
val rand_pow2 = apply(max, inc)
|
||||
|
||||
var res = UInt(mod-1)
|
||||
for (i <- mod-1 to 1 by -1)
|
||||
res = Mux(rand_pow2 < UInt(i*max/mod), UInt(i-1), res)
|
||||
res
|
||||
}
|
||||
}
|
||||
}
|
||||
|
Loading…
Reference in New Issue
Block a user