Merge remote-tracking branch 'origin/master' into ss-frontend

Also fixed bridx logic and zero-width wire logic.

Conflicts:
	src/main/scala/btb.scala

rocket/src/main/scala/btb.scala

@@ -53,10 +53,10 @@ class BHTResp extends Bundle with BTBParameters {
 // The counter table:
 //    - each counter corresponds with the "fetch pc" (not the PC of the branch). 
 //    - updated when a branch resolves (and BTB was a hit for that branch).
-//      The updating branch must provide its "fetch pc" in addition to its own PC.
+//      The updating branch must provide its "fetch pc".
 class BHT(nbht: Int) {
   val nbhtbits = log2Up(nbht)
-  def get(addr: UInt, bridx: UInt, update: Bool): BHTResp = {
+  def get(addr: UInt, update: Bool): BHTResp = {
     val res = new BHTResp
     val index = addr(nbhtbits+1,2) ^ history
     res.value := table(index)
@@ -78,7 +78,8 @@ class BHT(nbht: Int) {
 // BTB update occurs during branch resolution.
 //  - "pc" is what future fetch PCs will tag match against.
 //  - "br_pc" is the PC of the branch instruction.
-//  - "bridx" is the low-order PC bits of the predicted branch.
+//  - "bridx" is the low-order PC bits of the predicted branch (after 
+//    shifting off the lowest log(inst_bytes) bits off).
 //  - "resp.mask" provides a mask of valid instructions (instructions are
 //      masked off by the predicted taken branch).
 class BTBUpdate extends Bundle with BTBParameters {
@@ -91,7 +92,7 @@ class BTBUpdate extends Bundle with BTBParameters {
   val isCall = Bool()
   val isReturn = Bool()
   val br_pc = UInt(width = vaddrBits)
-  val incorrectTarget = Bool()
+  val mispredict = Bool()
 }
 
 class BTBResp extends Bundle with BTBParameters {
@@ -157,8 +158,8 @@ class BTB extends Module with BTBParameters {
   }
 
   val updateHit = r_update.bits.prediction.valid
-  val updateValid = r_update.bits.incorrectTarget || updateHit && Bool(nBHT > 0)
-  val updateTarget = updateValid && r_update.bits.incorrectTarget
+  val updateValid = r_update.bits.mispredict || updateHit && Bool(nBHT > 0)
+  val updateTarget = updateValid && r_update.bits.mispredict && r_update.bits.taken
 
   val useUpdatePageHit = updatePageHit.orR
   val doIdxPageRepl = updateTarget && !useUpdatePageHit
@@ -194,7 +195,11 @@ class BTB extends Module with BTBParameters {
       tgtPages(waddr) := tgtPageUpdate
       useRAS(waddr) := r_update.bits.isReturn
       isJump(waddr) := r_update.bits.isJump
-      brIdx(waddr)  := r_update.bits.br_pc
+      if (params(FetchWidth) == 1) {
+         brIdx(waddr) := UInt(0)
+      } else {
+         brIdx(waddr) := r_update.bits.br_pc >> log2Up(params(CoreInstBits)/8)
+      }
     }
 
     require(nPages % 2 == 0)
@@ -226,11 +231,11 @@ class BTB extends Module with BTBParameters {
 
   if (nBHT > 0) {
     val bht = new BHT(nBHT)
-    val res = bht.get(io.req.bits.addr, brIdx(io.resp.bits.entry), io.req.valid && hits.orR && !Mux1H(hits, isJump))
+    val res = bht.get(io.req.bits.addr, io.req.valid && hits.orR && !Mux1H(hits, isJump))
     val update_btb_hit = io.update.bits.prediction.valid
     when (io.update.valid && update_btb_hit && !io.update.bits.isJump) {
       bht.update(io.update.bits.pc, io.update.bits.prediction.bits.bht,
-                 io.update.bits.taken, io.update.bits.incorrectTarget)
+                 io.update.bits.taken, io.update.bits.mispredict)
     }
     when (!res.value(0) && !Mux1H(hits, isJump)) { io.resp.bits.taken := false }
     io.resp.bits.bht := res

rocket/src/main/scala/csr.scala

@@ -113,10 +113,7 @@ class CSRFile extends Module
     val map = for ((v, i) <- CSRs.all.zipWithIndex)
       yield v -> UInt(BigInt(1) << i)
     val out = ROM(map)(addr)
-    val a = Array.fill(CSRs.all.max+1)(null.asInstanceOf[Bool])
-    for (i <- 0 until CSRs.all.size)
-      a(CSRs.all(i)) = out(i)
-    a
+    Map((CSRs.all zip out.toBools):_*)
   }
 
   val wen = cpu_req_valid || host_pcr_req_fire && host_pcr_bits.rw

rocket/src/main/scala/ctrl.scala

@@ -652,11 +652,11 @@ class Control extends Module
     Mux(replay_wb,        PC_WB,  // replay
                           PC_MEM)))
 
-  io.imem.btb_update.valid := mem_reg_branch || mem_reg_jal || mem_reg_jalr
+  io.imem.btb_update.valid := (mem_reg_branch || io.imem.btb_update.bits.isJump) && !take_pc_wb
   io.imem.btb_update.bits.prediction.valid := mem_reg_btb_hit
   io.imem.btb_update.bits.prediction.bits := mem_reg_btb_resp
-  io.imem.btb_update.bits.taken := mem_reg_jal || mem_reg_branch && io.dpath.mem_br_taken
-  io.imem.btb_update.bits.incorrectTarget := take_pc_mem
+  io.imem.btb_update.bits.taken := mem_reg_branch && io.dpath.mem_br_taken || io.imem.btb_update.bits.isJump
+  io.imem.btb_update.bits.mispredict := take_pc_mem
   io.imem.btb_update.bits.isJump := mem_reg_jal || mem_reg_jalr
   io.imem.btb_update.bits.isCall := mem_reg_wen && io.dpath.mem_waddr(0)
   io.imem.btb_update.bits.isReturn := mem_reg_jalr && io.dpath.mem_rs1_ra

rocket/src/main/scala/icache.scala

@@ -114,7 +114,7 @@ class Frontend extends FrontendModule
   }
 
   val all_ones = UInt((1 << coreFetchWidth)-1)
-  val msk_pc = all_ones << s2_pc(log2Up(coreFetchWidth)-1+2,2)
+  val msk_pc = if (coreFetchWidth == 1) all_ones else all_ones << s2_pc(log2Up(coreFetchWidth) -1+2,2)
   io.cpu.resp.bits.mask := msk_pc & btb.io.resp.bits.mask
 
   io.cpu.resp.bits.xcpt_ma := s2_pc(log2Up(coreInstBytes)-1,0) != UInt(0)