fix(frontend,cache): Fix warning of read-only return value of .asTypeOf

The chisel3 has marked retrun value of .asTypeOf as "deprecated
read-only" in #4198:

 ### [W008] Return values of asTypeOf will soon be read-only
 This warning indicates that the result of a call to `.asTypeOf(_)` is
 being used as the destination for a connection. It can be fixed by
 instantiating a wire.

Fix the usage of asTypeOf in cache/frontent as suggested by the warning.

Signed-off-by: Jiuyue Ma <[email protected]>

src/main/scala/xiangshan/cache/mmu/PageTableWalker.scala

@@ -177,13 +177,13 @@ class PTW()(implicit p: Parameters) extends XSModule with HasPtwConst with HasPe
   val gvpn_gpf = !(hptw_pageFault || hptw_accessFault ) && Mux(s2xlate && io.csr.hgatp.mode === Sv39x4, full_gvpn(ptePPNLen - 1, GPAddrBitsSv39x4 - offLen) =/= 0.U, Mux(s2xlate && io.csr.hgatp.mode === Sv48x4, full_gvpn(ptePPNLen - 1, GPAddrBitsSv48x4 - offLen) =/= 0.U, false.B))
   val guestFault = hptw_pageFault || hptw_accessFault || gvpn_gpf
   val hpaddr = Cat(hptw_resp.genPPNS2(get_pn(gpaddr)), get_off(gpaddr))
-  val fake_h_resp = 0.U.asTypeOf(new HptwResp)
+  val fake_h_resp = WireInit(0.U.asTypeOf(new HptwResp))
   fake_h_resp.entry.tag := get_pn(gpaddr)
   fake_h_resp.entry.vmid.map(_ := io.csr.hgatp.vmid)
   fake_h_resp.gpf := true.B
 
   val pte_valid = RegInit(false.B)  // avoid l1tlb pf from stage1 when gpf happens in the first s2xlate in PTW
-  val fake_pte = 0.U.asTypeOf(new PteBundle())
+  val fake_pte = WireInit(0.U.asTypeOf(new PteBundle()))
   fake_pte.perm.v := false.B // tell L1TLB this is fake pte
   fake_pte.ppn := ppn(ppnLen - 1, 0)
   fake_pte.ppn_high := ppn(ptePPNLen - 1, ppnLen)

src/main/scala/xiangshan/frontend/ITTAGE.scala

@@ -504,29 +504,32 @@ class ITTage(implicit p: Parameters) extends BaseITTage {
   val update = Wire(new BranchPredictionUpdate)
   update := RegEnable(io.update.bits, io.update.valid)
 
+  // meta is splited by composer
+  val updateMeta = WireInit(update.meta.asTypeOf(new ITTageMeta))
+
   // The pc register has been moved outside of predictor, pc field of update bundle and other update data are not in the same stage
   // so io.update.bits.pc is used directly here
   val update_pc = io.update.bits.pc
 
   // To improve Clock Gating Efficiency
   val u_meta = io.update.bits.meta.asTypeOf(new ITTageMeta)
-  update.meta.asTypeOf(new ITTageMeta).provider.bits := RegEnable(
+  updateMeta.provider.bits := RegEnable(
     u_meta.provider.bits,
     io.update.valid && u_meta.provider.valid
   )
-  update.meta.asTypeOf(new ITTageMeta).providerTarget := RegEnable(
+  updateMeta.providerTarget := RegEnable(
     u_meta.providerTarget,
     io.update.valid && u_meta.provider.valid
   )
-  update.meta.asTypeOf(new ITTageMeta).allocate.bits := RegEnable(
+  updateMeta.allocate.bits := RegEnable(
     u_meta.allocate.bits,
     io.update.valid && u_meta.allocate.valid
   )
-  update.meta.asTypeOf(new ITTageMeta).altProvider.bits := RegEnable(
+  updateMeta.altProvider.bits := RegEnable(
     u_meta.altProvider.bits,
     io.update.valid && u_meta.altProvider.valid
   )
-  update.meta.asTypeOf(new ITTageMeta).altProviderTarget := RegEnable(
+  updateMeta.altProviderTarget := RegEnable(
     u_meta.altProviderTarget,
     io.update.valid && u_meta.provider.valid && u_meta.altProvider.valid && u_meta.providerCtr === 0.U
   )
@@ -543,9 +546,6 @@ class ITTage(implicit p: Parameters) extends BaseITTage {
         numBr - 1
       )
 
-  // meta is splited by composer
-  val updateMeta = update.meta.asTypeOf(new ITTageMeta)
-
   val updateMask            = WireInit(0.U.asTypeOf(Vec(ITTageNTables, Bool())))
   val updateUMask           = WireInit(0.U.asTypeOf(Vec(ITTageNTables, Bool())))
   val updateResetU          = WireInit(false.B)

src/main/scala/xiangshan/frontend/Tage.scala

@@ -706,29 +706,30 @@ class Tage(implicit p: Parameters) extends BaseTage {
     VecInit((0 until TageBanks).map(w =>
       io.update.bits.ftb_entry.brValids(w) && io.update.valid
     )) // io.update.bits.ftb_entry.always_taken has timing issues(FTQEntryGen)
-  val u_meta = io.update.bits.meta.asTypeOf(new TageMeta)
+  val u_meta     = io.update.bits.meta.asTypeOf(new TageMeta)
+  val updateMeta = WireInit(update.meta.asTypeOf(new TageMeta))
   for (i <- 0 until numBr) {
-    update.meta.asTypeOf(new TageMeta).providers(i).bits := RegEnable(
+    updateMeta.providers(i).bits := RegEnable(
       u_meta.providers(i).bits,
       u_meta.providers(i).valid && u_valids_for_cge(i)
     )
-    update.meta.asTypeOf(new TageMeta).providerResps(i) := RegEnable(
+    updateMeta.providerResps(i) := RegEnable(
       u_meta.providerResps(i),
       u_meta.providers(i).valid && u_valids_for_cge(i)
     )
-    update.meta.asTypeOf(new TageMeta).altUsed(i) := RegEnable(u_meta.altUsed(i), u_valids_for_cge(i))
-    update.meta.asTypeOf(new TageMeta).allocates(i) := RegEnable(
+    updateMeta.altUsed(i) := RegEnable(u_meta.altUsed(i), u_valids_for_cge(i))
+    updateMeta.allocates(i) := RegEnable(
       u_meta.allocates(i),
       io.update.valid && io.update.bits.mispred_mask(i)
     )
   }
   if (EnableSC) {
     for (w <- 0 until TageBanks) {
-      update.meta.asTypeOf(new TageMeta).scMeta.get.scPreds(w) := RegEnable(
+      updateMeta.scMeta.get.scPreds(w) := RegEnable(
         u_meta.scMeta.get.scPreds(w),
         u_valids_for_cge(w) && u_meta.providers(w).valid
       )
-      update.meta.asTypeOf(new TageMeta).scMeta.get.ctrs(w) := RegEnable(
+      updateMeta.scMeta.get.ctrs(w) := RegEnable(
         u_meta.scMeta.get.ctrs(w),
         u_valids_for_cge(w) && u_meta.providers(w).valid
       )
@@ -741,8 +742,6 @@ class Tage(implicit p: Parameters) extends BaseTage {
       !(PriorityEncoder(update.br_taken_mask) < w.U)
   ))
 
-  val updateMeta = update.meta.asTypeOf(new TageMeta)
-
   val updateMask    = WireInit(0.U.asTypeOf(Vec(numBr, Vec(TageNTables, Bool()))))
   val updateUMask   = WireInit(0.U.asTypeOf(Vec(numBr, Vec(TageNTables, Bool()))))
   val updateResetU  = WireInit(0.U.asTypeOf(Vec(numBr, Bool()))) // per predictor