ftq: modify jmpTarget in FtbEntry whenever jalr target changes

* previously we only modify jmpTarget on misprediction, and that's
  because we only use ftb to predict jalr target. However, with the
  presence of an indirect branch predictor, there exists such case
  that an indirect branch is correctly predicted when the target in
  ftb entry is wrong.

src/main/scala/xiangshan/frontend/NewFtq.scala

@@ -359,8 +359,9 @@ class FTBEntryGen(implicit p: Parameters) extends XSModule with HasBackendRedire
   }
 
   val old_entry_jmp_target_modified = WireInit(oe)
-  val jalr_mispredicted = cfi_is_jalr && io.mispredict_vec(io.pd.jmpOffset)
-  when (jalr_mispredicted) {
+  val old_target = oe.getJmpTarget(io.start_addr)
+  val jalr_target_modified = cfi_is_jalr && (old_target =/= io.target) // TODO: pass full jalr target
+  when (jalr_target_modified) {
     old_entry_jmp_target_modified.setByJmpTarget(io.start_addr, io.target)
     old_entry_jmp_target_modified.always_taken := 0.U.asTypeOf(Vec(numBr, Bool()))
   }
@@ -378,7 +379,7 @@ class FTBEntryGen(implicit p: Parameters) extends XSModule with HasBackendRedire
 
   val derived_from_old_entry =
     Mux(is_new_br, old_entry_modified,
-      Mux(jalr_mispredicted, old_entry_jmp_target_modified, old_entry_always_taken))
+      Mux(jalr_target_modified, old_entry_jmp_target_modified, old_entry_always_taken))
 
   
   io.new_entry := Mux(!hit, init_entry, derived_from_old_entry)
@@ -394,9 +395,9 @@ class FTBEntryGen(implicit p: Parameters) extends XSModule with HasBackendRedire
 
   // for perf counters
   io.is_init_entry := !hit
-  io.is_old_entry := hit && !is_new_br && !jalr_mispredicted && !always_taken_modified
+  io.is_old_entry := hit && !is_new_br && !jalr_target_modified && !always_taken_modified
   io.is_new_br := hit && is_new_br
-  io.is_jalr_target_modified := hit && jalr_mispredicted
+  io.is_jalr_target_modified := hit && jalr_target_modified
   io.is_always_taken_modified := hit && always_taken_modified
   io.is_br_full := hit && is_new_br && br_full
 }