LoadQueue: fix rollback gen logic

Former rollback will now cancel later rollback correctly

src/main/scala/utils/CircularQueuePtr.scala

@@ -68,4 +68,8 @@ trait HasCircularQueuePtrHelper {
   def isAfter[T <: CircularQueuePtr](left: T, right: T): Bool = {
     Mux(left.flag === right.flag, left.value > right.value, left.value < right.value)
   }
+
+  def isBefore[T <: CircularQueuePtr](left: T, right: T): Bool = {
+    Mux(left.flag === right.flag, left.value < right.value, left.value > right.value)
+  }
 }

src/main/scala/xiangshan/mem/lsqueue/LoadQueue.scala

@@ -509,8 +509,8 @@ class LoadQueue extends XSModule
   val rollbackValidVecChecked = Wire(Vec(3, Bool()))
   for(((v, uop), idx) <- rollbackValidVec.zip(rollbackUopVec).zipWithIndex) {
     rollbackValidVecChecked(idx) := v && 
-      (!lastCycleRedirect.valid || !isAfter(uop.roqIdx, lastCycleRedirect.bits.roqIdx)) &&
-      (!lastlastCycleRedirect.valid || !isAfter(uop.roqIdx, lastlastCycleRedirect.bits.roqIdx))
+      (!lastCycleRedirect.valid || isBefore(uop.roqIdx, lastCycleRedirect.bits.roqIdx)) &&
+      (!lastlastCycleRedirect.valid || isBefore(uop.roqIdx, lastlastCycleRedirect.bits.roqIdx))
   }
 
   io.rollback.bits.roqIdx := rollbackUop.roqIdx