Stack looks like this:
-scnorm - FPDIVSpecialCasesDeNorm ispec FPADDBaseData ospec FPSCData
- StageChain: FPDIVSpecialCasesMod,
- FPAddDeNormMod
-
-pipediv0 - FPDivStages(start=true) ispec FPSCData ospec FPDivStage0Data
- StageChain: FPDivStage0Mod,
- FPDivStage1Mod,
- ...
- FPDivStage1Mod
-
-pipediv1 - FPDivStages() ispec FPDivStage0Data ospec FPDivStage0Data
- StageChain: FPDivStage1Mod,
- ...
- FPDivStage1Mod
+scnorm - FPDIVSpecialCasesDeNorm ispec FPADDBaseData
+------ ospec FPSCData
+
+ StageChain: FPDIVSpecialCasesMod,
+ FPAddDeNormMod
+
+pipediv0 - FPDivStagesSetup ispec FPSCData
+-------- ospec DivPipeCoreInterstageData
+
+ StageChain: FPDivStage0Mod,
+ DivPipeSetupStage,
+ DivPipeCalculateStage,
+ ...
+ DivPipeCalculateStage
+
+pipediv1 - FPDivStagesIntermediate ispec DivPipeCoreInterstageData
+-------- ospec DivPipeCoreInterstageData
+
+ StageChain: DivPipeCalculateStage,
+ ...
+ DivPipeCalculateStage
...
...
-pipediv5 - FPDivStages(end=true ispec FPDivStage0Data ospec FPAddStage1Data
- StageChain: FPDivStage1Mod,
- ...
- FPDivStage1Mod,
- FPDivStage2Mod
+pipediv5 - FPDivStageFinal ispec FPDivStage0Data
+-------- ospec FPAddStage1Data
+
+ StageChain: DivPipeCalculateStage,
+ ...
+ DivPipeCalculateStage,
+ DivPipeFinalStage,
+ FPDivStage2Mod
-normpack - FPNormToPack ispec FPAddStage1Data ospec FPPackData
- StageChain: Norm1ModSingle,
- RoundMod,
- CorrectionsMod,
- PackMod
+normpack - FPNormToPack ispec FPAddStage1Data
+-------- ospec FPPackData
-the number of combinatorial StageChains (n_combinatorial_stages) in
+ StageChain: Norm1ModSingle,
+ RoundMod,
+ CorrectionsMod,
+ PackMod
+
+the number of combinatorial StageChains (n_comb_stages) in
FPDivStages is an argument arranged to get the length of the whole
pipeline down to sane numbers.
+
+the reason for keeping the number of stages down is that for every
+pipeline clock delay, a corresponding ReservationStation is needed.
+if there are 24 pipeline stages, we need a whopping TWENTY FOUR
+RS's. that's far too many. 6 is just about an acceptable number.
+even 8 is starting to get alarmingly high.
"""
from nmigen import Module
from ieee754.fpcommon.pack import FPPackData
from ieee754.fpcommon.normtopack import FPNormToPack
from .specialcases import FPDIVSpecialCasesDeNorm
-from .divstages import FPDivStages
-
+from .divstages import (FPDivStagesSetup,
+ FPDivStagesIntermediate,
+ FPDivStagesFinal)
class FPDIVBasePipe(ControlBase):
- def __init__(self, width, pspec):
+ def __init__(self, pspec):
ControlBase.__init__(self)
- self.pipestart = FPDIVSpecialCasesDeNorm(width, pspec)
+ self.pspec = pspec
+
+ def elaborate(self, platform):
+ m = ControlBase.elaborate(self, platform)
+
pipechain = []
- n_stages = 6 # TODO
- n_combinatorial_stages = 2 # TODO
+ n_stages = 6 # TODO (depends on width)
+ n_comb_stages = 3 # TODO (depends on how many RS's we want)
+ # to which the answer: "as few as possible"
+ # is required. too many ReservationStations
+ # means "big problems".
+
for i in range(n_stages):
- begin = i == 0 # needs to convert input from pipestart ospec
- end = i == n_stages - 1 # needs to convert output to pipeend ispec
- pipechain.append(FPDivStages(width, pspec,
- n_combinatorial_stages,
- begin, end))
- self.pipechain = pipechain
- self.pipeend = FPNormToPack(width, pspec)
- self._eqs = self.connect([self.pipestart] + pipechain + [self.pipeend])
+ # needs to convert input from pipestart ospec
+ if i == 0:
+ kls = FPDivStagesSetup
+ n_comb_stages -= 1 # reduce due to work done at start
- def elaborate(self, platform):
- m = ControlBase.elaborate(self, platform)
- m.submodules.scnorm = self.pipestart
- for i, p in enumerate(self.pipechain):
+ # needs to convert output to pipeend ispec
+ elif i == n_stages - 1:
+ kls = FPDivStagesFinal
+ n_comb_stages -= 1 # FIXME - reduce due to work done at end?
+
+ # intermediary stage
+ else:
+ kls = FPDivStagesIntermediate
+
+ pipechain.append(kls(self.pspec, n_comb_stages))
+
+ # start and end: unpack/specialcases then normalisation/packing
+ pipestart = FPDIVSpecialCasesDeNorm(self.pspec)
+ pipeend = FPNormToPack(self.pspec)
+
+ # add submodules
+ m.submodules.scnorm = pipestart
+ for i, p in enumerate(pipechain):
setattr(m.submodules, "pipediv%d" % i, p)
- m.submodules.normpack = self.pipeend
- m.d.comb += self._eqs
+ m.submodules.normpack = pipeend
+
+ # ControlBase.connect creates the "eqs" needed to connect each pipe
+ m.d.comb += self.connect([pipestart] + pipechain + [pipeend])
+
return m
then be used to change the behaviour of the pipeline.
"""
def __init__(self, width, num_rows, op_wid=0):
- self.width = width
self.id_wid = num_bits(width)
- self.pspec = {'id_wid': self.id_wid, 'op_wid': op_wid}
- self.alu = FPDIVBasePipe(width, self.pspec)
+ self.pspec = {'width': width, 'id_wid': self.id_wid, 'op_wid': op_wid}
+ self.alu = FPDIVBasePipe(self.pspec)
ReservationStations.__init__(self, num_rows)
def i_specfn(self):
- return FPADDBaseData(self.width, self.pspec)
+ return FPADDBaseData(self.pspec)
def o_specfn(self):
- return FPPackData(self.width, self.pspec)
+ return FPPackData(self.pspec)
projects / ieee754fpu.git / blobdiff