Prioritize co-processor FP reqs over FPU reqs

Co-processor reqs will generally be post-commit, from older instructions.
Prioritizing these requests avoids deadlock cases.

src/main/scala/rocket/RocketCore.scala

@@ -1093,7 +1093,7 @@ class Rocket(tile: RocketTile)(implicit p: Parameters) extends CoreModule()(p)
 
   io.fpu.valid := !ctrl_killd && id_ctrl.fp
   io.fpu.killx := ctrl_killx
-  io.fpu.killm := killm_common
+  io.fpu.killm := killm_common || vec_kill_mem
   io.fpu.inst := id_inst(0)
   io.fpu.fromint_data := ex_rs(0)
   io.fpu.ll_resp_val := dmem_resp_valid && dmem_resp_fpu
@@ -1122,7 +1122,7 @@ class Rocket(tile: RocketTile)(implicit p: Parameters) extends CoreModule()(p)
     v.ex.rs2 := ex_rs(1)
     v.ex.pc := ex_reg_pc
     v.mem.frs1 := io.fpu.store_data
-    v.killm := killm_common
+    v.killm := killm_common || fpu_kill_mem
     v.status := csr.io.status
   }
 

src/main/scala/tile/FPU.scala

@@ -988,7 +988,7 @@ class FPU(cfg: FPUParams)(implicit p: Parameters) extends FPUModule()(p) {
     s"FPU only supports coprocessor if FMA pipes have uniform latency ${pipes.map(_.lat)}")
   // Avoid structural hazards and nacking of external requests
   // toint responds in the MEM stage, so an incoming toint can induce a structural hazard against inflight FMAs
-  io.cp_req.ready := !ex_reg_valid && !(cp_ctrl.toint && wen =/= 0.U) && !divSqrt_inFlight
+  io.cp_req.ready := !(cp_ctrl.toint && wen =/= 0.U) && !divSqrt_inFlight
 
   val wb_toint_valid = wb_reg_valid && wb_ctrl.toint
   val wb_toint_exc = RegEnable(fpiu.io.out.bits.exc, mem_ctrl.toint)
@@ -1000,7 +1000,7 @@ class FPU(cfg: FPUParams)(implicit p: Parameters) extends FPUModule()(p) {
 
   val divSqrt_write_port_busy = (mem_ctrl.div || mem_ctrl.sqrt) && wen.orR
   io.fcsr_rdy := !(ex_reg_valid && ex_ctrl.wflags || mem_reg_valid && mem_ctrl.wflags || wb_reg_valid && wb_ctrl.toint || wen.orR || divSqrt_inFlight)
-  io.nack_mem := (write_port_busy || divSqrt_write_port_busy || divSqrt_inFlight) && !mem_cp_valid
+  io.nack_mem := (write_port_busy || divSqrt_write_port_busy || divSqrt_inFlight || mem_cp_valid)
   io.dec <> id_ctrl
   def useScoreboard(f: ((Pipe, Int)) => Bool) = pipes.zipWithIndex.filter(_._1.lat > 3).map(x => f(x)).fold(false.B)(_||_)
   io.sboard_set := wb_reg_valid && !wb_cp_valid && RegNext(useScoreboard(_._1.cond(mem_ctrl)) || mem_ctrl.div || mem_ctrl.sqrt || mem_ctrl.vec)