Implement Ibuffer

src/main/scala/xiangshan/frontend/Ibuffer.scala

-package xiangshan.frontend
-
-import chisel3._
-import chisel3.util._
-
-import xiangshan._
-import xiangshan.utils._
-
-class Ibuffer extends XSModule with NeedImpl {
-  val io = IO(new Bundle() {
-    val flush = Input(Bool())
-    val in = Flipped(DecoupledIO(new FetchPacket))
-    val out = Vec(DecodeWidth, DecoupledIO(new CtrlFlow))
-  })
+package xiangshan.frontend
+
+import chisel3._
+import chisel3.util._
+
+import xiangshan._
+import xiangshan.utils._
+
+class Ibuffer extends XSModule {
+  val io = IO(new Bundle() {
+    val flush = Input(Bool())
+    val in = Flipped(DecoupledIO(new FetchPacket))
+    val out = Vec(DecodeWidth, DecoupledIO(new CtrlFlow))
+  })
+
+  val debug = false
+  if(debug){
+//    printf("\n------New Cycle------\n")
+    when(io.in.valid) {
+      printf("cache data:\n")
+      for (i <- 0 until FetchWidth) {
+        printf("%b\n", io.in.bits.instrs(i))
+      }
+      printf("\n")
+    }
+  }
+
+  // ignore
+  for(i <- 0 until DecodeWidth) {
+    io.out(i).bits.exceptionVec := DontCare
+    io.out(i).bits.intrVec := DontCare
+    io.out(i).bits.isBr := DontCare
+  }
+
+  // ibuf define
+  val ibuf = RegInit(VecInit(Seq.fill(IBufSize*2)(0.U(16.W))))
+  val ibuf_pc = RegInit(VecInit(Seq.fill(IBufSize*2)(0.U(VAddrBits.W))))
+  val ibuf_valid = RegInit(VecInit(Seq.fill(IBufSize*2)(false.B)))
+  val head_ptr = RegInit(0.U(log2Up(IBufSize*2).W))
+  val tail_ptr = RegInit(0.U(log2Up(IBufSize*2).W))
+
+  // true: Last operation is enqueue
+  // false: Last operation is deq_ueue
+  val last_enq = RegInit(false.B)
+  val full = head_ptr === tail_ptr && last_enq
+  val empty = head_ptr === tail_ptr && !last_enq
+  val enqValid = !io.flush && io.in.valid && !full && !ibuf_valid(tail_ptr + (FetchWidth*2).U)
+  val deqValid = !io.flush && !empty && io.out.map(x => x.ready).reduce(_||_)
+
+  io.in.ready := enqValid
+
+  // enque
+  when(enqValid) {
+    if(debug) {
+      printf("\n*****Enque start*****\n")
+    }
+
+    var enq_idx = 0.U(log2Up(FetchWidth*2+1).W)
+    for(i <- 0 until FetchWidth) {
+      when(io.in.bits.mask(i)) {
+        ibuf(tail_ptr + enq_idx) := io.in.bits.instrs(i)(15,0)
+        ibuf_pc(tail_ptr + enq_idx) := io.in.bits.pc + enq_idx + enq_idx
+        ibuf_valid(tail_ptr + enq_idx) := true.B
+
+        ibuf(tail_ptr + enq_idx+1.U) := io.in.bits.instrs(i)(31,16)
+        ibuf_pc(tail_ptr + enq_idx+1.U) := io.in.bits.pc + enq_idx + enq_idx + 2.U
+        ibuf_valid(tail_ptr + enq_idx+1.U) := true.B
+
+        if(debug) {
+          printf("%b\n", io.in.bits.instrs(i)(15,0))
+          printf("%b\n", io.in.bits.instrs(i)(31,16))
+        }
+      }
+      enq_idx = enq_idx + io.in.bits.mask(i) + io.in.bits.mask(i)
+    }
+
+    tail_ptr := tail_ptr + enq_idx
+    last_enq := true.B
+
+    if(debug) {
+      printf("tail_ptr: %d\n", tail_ptr + enq_idx)
+    }
+  }
+
+  // deque
+  when(deqValid) {
+    if(debug) {
+      printf("\n*****Deque start*****\n")
+      printf("Last head_ptr: %d, tail_ptr: %d\n", head_ptr, tail_ptr)
+    }
+
+    var deq_idx = 0.U(log2Up(DecodeWidth*2+1).W)
+    for(i <- 0 until DecodeWidth) {
+      when(io.out(i).ready && ibuf_valid(head_ptr + deq_idx)) {
+        when(ibuf(head_ptr + deq_idx)(1,0) =/= "b11".U) {
+          // is RVC
+          io.out(i).bits.instr := Cat(0.U(16.W), ibuf(head_ptr + deq_idx))
+          io.out(i).bits.pc := ibuf_pc(head_ptr + deq_idx)
+          if(debug) {
+            printf("RCV: %b    ", Cat(0.U(16.W), ibuf(head_ptr + deq_idx)))
+            printf("PC: %d\n", ibuf_pc(head_ptr + deq_idx))
+          }
+          io.out(i).bits.isRVC := true.B
+          io.out(i).valid := true.B
+          ibuf_valid(head_ptr + deq_idx) := false.B
+        }.elsewhen(ibuf_valid(head_ptr + deq_idx + 1.U)) {
+          // isn't RVC
+          io.out(i).bits.instr := Cat(ibuf(head_ptr + deq_idx+1.U), ibuf(head_ptr + deq_idx))
+          io.out(i).bits.pc := ibuf_pc(head_ptr + deq_idx)
+          if(debug) {
+            printf("NOT RVC: %b    ", Cat(ibuf(head_ptr + deq_idx+1.U), ibuf(head_ptr + deq_idx)))
+            printf("PC: %d\n", ibuf_pc(head_ptr + deq_idx))
+          }
+          io.out(i).bits.isRVC := false.B
+          io.out(i).valid := true.B
+          ibuf_valid(head_ptr + deq_idx) := false.B
+          ibuf_valid(head_ptr + deq_idx+1.U) := false.B
+        }.otherwise {
+          // half inst keep in buffer
+          io.out(i).bits.instr := 0.U(32.W)
+          if(debug) {
+            printf("This is half inst\n")
+          }
+          io.out(i).bits.pc := 0.U(VAddrBits.W)
+          io.out(i).bits.isRVC := false.B
+          io.out(i).valid := false.B
+        }
+      }.otherwise {
+        if(debug) {
+          printf("This output is not ready, or buffer is empty\n")
+        }
+
+        io.out(i).bits.instr := 0.U
+        io.out(i).bits.pc := 0.U
+        io.out(i).bits.isRVC := false.B
+        io.out(i).valid := false.B
+      }
+
+      if(debug) {
+        printf("deq_idx: %d\n", deq_idx)
+      }
+
+      // When can't deque, deq_idx+0
+      // when RVC deque, deq_idx+1
+      // when not RVC deque, deq_idx+2
+      // when only have half inst, keep it in buffer
+      deq_idx = deq_idx +
+                (io.out(i).ready && ibuf_valid(head_ptr + deq_idx) && ibuf(head_ptr + deq_idx)(1,0) =/= "b11".U) +
+                (io.out(i).ready && ibuf_valid(head_ptr + deq_idx) && !(ibuf(head_ptr + deq_idx)(1,0) =/= "b11".U) && ibuf_valid(head_ptr + deq_idx + 1.U)) +
+                (io.out(i).ready && ibuf_valid(head_ptr + deq_idx) && !(ibuf(head_ptr + deq_idx)(1,0) =/= "b11".U) && ibuf_valid(head_ptr + deq_idx + 1.U))
+    }
+    head_ptr := head_ptr + deq_idx
+    if(debug) {
+      printf("head_ptr: %d\n", head_ptr + deq_idx)
+    }
+    last_enq := false.B
+  }.otherwise {
+    for(i <- 0 until DecodeWidth) {
+      io.out(i).bits.instr := 0.U
+      io.out(i).bits.pc := 0.U
+      io.out(i).bits.isRVC := false.B
+      io.out(i).valid := false.B
+    }
+  }
+
+  // flush
+  when(io.flush) {
+    for(i <- 0 until IBufSize) {
+      ibuf_valid(i) := false.B
+      head_ptr := 0.U
+      tail_ptr := 0.U
+    }
+
+    for(i <- 0 until DecodeWidth) {
+      io.out(i).valid := false.B
+    }
+  }
 }
\ No newline at end of file