Faster pipeline arbitration logic (200 Mhz on cyclone IV c6)
Branch plugin with jump in execute or memory stages (parameter)
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c6610ea454
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@ -108,15 +108,12 @@ trait Pipeline {
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val stageBefore = stages(stageIndex - 1)
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val stage = stages(stageIndex)
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when(!stage.arbitration.isStuck) {
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when(!stage.arbitration.isStuck || stage.arbitration.removeIt) {
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stage.arbitration.isValid := False
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}
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when(!stageBefore.arbitration.isStuck && !stageBefore.arbitration.removeIt) {
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stage.arbitration.isValid := stageBefore.arbitration.isValid
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}
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when(stage.arbitration.removeIt){
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stage.arbitration.isValid := False
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}
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}
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}
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@ -257,6 +257,7 @@ class DecoderSimplePlugin extends Plugin[VexRiscv] with DecoderService {
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offset = 0
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stageables.foreach(e => {
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insert(e).assignFromBits(decodedBits(offset, e.dataType.getBitsWidth bits))
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// insert(e).assignFromBits(RegNext(decodedBits(offset, e.dataType.getBitsWidth bits)))
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offset += e.dataType.getBitsWidth
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})
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}
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@ -273,13 +274,14 @@ class DecoderSimplePlugin extends Plugin[VexRiscv] with DecoderService {
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}
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}
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class NoPredictionBranchPlugin extends Plugin[VexRiscv]{
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class NoPredictionBranchPlugin(earlyBranch : Boolean) extends Plugin[VexRiscv]{
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object BranchCtrlEnum extends SpinalEnum(binarySequential){
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val INC,B,JAL,JALR = newElement()
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}
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object BRANCH_CTRL extends Stageable(BranchCtrlEnum())
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object BRANCH_SOLVED extends Stageable(BranchCtrlEnum())
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object BRANCH_CALC extends Stageable(UInt(32 bits))
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var jumpInterface : Flow[UInt] = null
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@ -345,17 +347,24 @@ class NoPredictionBranchPlugin extends Plugin[VexRiscv]{
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)
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val imm = IMM(input(INSTRUCTION))
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jumpInterface.valid := arbitration.isFiring && input(BRANCH_SOLVED) =/= BranchCtrlEnum.INC
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jumpInterface.payload := input(BRANCH_SOLVED).mux(
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insert(BRANCH_CALC) := input(BRANCH_SOLVED).mux(
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BranchCtrlEnum.JAL -> (input(PC) + imm.j_sext.asUInt),
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BranchCtrlEnum.JALR -> (input(REG1).asUInt + imm.i_sext.asUInt),
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default -> (input(PC) + imm.b_sext.asUInt) //B
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)
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}
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when(jumpInterface.valid){
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val branchStage = if(earlyBranch) execute else memory
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branchStage plug new Area {
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import branchStage._
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jumpInterface.valid := arbitration.isFiring && input(BRANCH_SOLVED) =/= BranchCtrlEnum.INC
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jumpInterface.payload := input(BRANCH_CALC)
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when(jumpInterface.valid) {
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prefetch.arbitration.removeIt := True
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fetch.arbitration.removeIt := True
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decode.arbitration.removeIt := True
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fetch.arbitration.removeIt := True
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decode.arbitration.removeIt := True
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if(!earlyBranch) execute.arbitration.removeIt := True
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}
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}
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}
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@ -940,7 +949,7 @@ object TopLevel {
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new DBusSimplePlugin,
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// new HazardSimplePlugin(true,true,true,true),
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new HazardSimplePlugin(false, false, false, false),
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new NoPredictionBranchPlugin
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new NoPredictionBranchPlugin(false)
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)
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val toplevel = new VexRiscv(config)
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