diff --git a/src/main/scala/vexriscv/plugin/Mul16Plugin.scala b/src/main/scala/vexriscv/plugin/Mul16Plugin.scala new file mode 100644 index 0000000..f2a63c3 --- /dev/null +++ b/src/main/scala/vexriscv/plugin/Mul16Plugin.scala @@ -0,0 +1,119 @@ +package vexriscv.plugin + +import vexriscv._ +import vexriscv.plugin._ +import spinal.core._ + +/** + * A multiplication plugin using only 16-bit multiplications + */ +class Mul16Plugin extends Plugin[VexRiscv]{ + + object MUL_LL extends Stageable(UInt(32 bits)) + object MUL_LH extends Stageable(UInt(32 bits)) + object MUL_HL extends Stageable(UInt(32 bits)) + object MUL_HH extends Stageable(UInt(32 bits)) + + object MUL extends Stageable(Bits(64 bits)) + + object IS_MUL extends Stageable(Bool) + + override def setup(pipeline: VexRiscv): Unit = { + import Riscv._ + import pipeline.config._ + + + val actions = List[(Stageable[_ <: BaseType],Any)]( + SRC1_CTRL -> Src1CtrlEnum.RS, + SRC2_CTRL -> Src2CtrlEnum.RS, + REGFILE_WRITE_VALID -> True, + BYPASSABLE_EXECUTE_STAGE -> False, + BYPASSABLE_MEMORY_STAGE -> False, + RS1_USE -> True, + RS2_USE -> True, + IS_MUL -> True + ) + + val decoderService = pipeline.service(classOf[DecoderService]) + decoderService.addDefault(IS_MUL, False) + decoderService.add(List( + MULX -> actions + )) + + } + + override def build(pipeline: VexRiscv): Unit = { + import pipeline._ + import pipeline.config._ + + // Prepare signed inputs for the multiplier in the next stage. + // This will map them best to an FPGA DSP. + execute plug new Area { + import execute._ + val a,b = Bits(32 bit) + + a := input(SRC1) + b := input(SRC2) + + val aLow = a(15 downto 0).asUInt + val bLow = b(15 downto 0).asUInt + val aHigh = a(31 downto 16).asUInt + val bHigh = b(31 downto 16).asUInt + + insert(MUL_LL) := aLow * bLow + insert(MUL_LH) := aLow * bHigh + insert(MUL_HL) := aHigh * bLow + insert(MUL_HH) := aHigh * bHigh + } + + memory plug new Area { + import memory._ + + val ll = UInt(32 bits) + val lh = UInt(33 bits) + val hl = UInt(32 bits) + val hh = UInt(32 bits) + + ll := input(MUL_LL) + lh := input(MUL_LH).resized + hl := input(MUL_HL) + hh := input(MUL_HH) + + val hllh = lh + hl + insert(MUL) := ((hh ## ll(31 downto 16)).asUInt + hllh) ## ll(15 downto 0) + } + + writeBack plug new Area { + import writeBack._ + val aSigned,bSigned = Bool + switch(input(INSTRUCTION)(13 downto 12)) { + is(B"01") { + aSigned := True + bSigned := True + } + is(B"10") { + aSigned := True + bSigned := False + } + default { + aSigned := False + bSigned := False + } + } + + val a = (aSigned && input(SRC1).msb) ? input(SRC2).asUInt | U(0) + val b = (bSigned && input(SRC2).msb) ? input(SRC1).asUInt | U(0) + + when(arbitration.isValid && input(IS_MUL)){ + switch(input(INSTRUCTION)(13 downto 12)){ + is(B"00"){ + output(REGFILE_WRITE_DATA) := input(MUL)(31 downto 0) + } + is(B"01",B"10",B"11"){ + output(REGFILE_WRITE_DATA) := (((input(MUL)(63 downto 32)).asUInt + ~a) + (~b + 2)).asBits + } + } + } + } + } +}