From 66120cde6c6472598e94d7409a2f37c8b308b716 Mon Sep 17 00:00:00 2001
From: =youzi27 <=809891392@qq.com>
Date: Wed, 6 Dec 2023 13:36:29 +0800
Subject: [PATCH 1/2] Fix:epc[0] value is always 0

---
 src/main/scala/nutcore/backend/fu/CSR.scala | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/main/scala/nutcore/backend/fu/CSR.scala b/src/main/scala/nutcore/backend/fu/CSR.scala
index 3e594656..46bd3bb1 100644
--- a/src/main/scala/nutcore/backend/fu/CSR.scala
+++ b/src/main/scala/nutcore/backend/fu/CSR.scala
@@ -385,7 +385,9 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
 
     // User Trap Handling
     // MaskedRegMap(Uscratch, uscratch),
-    // MaskedRegMap(Uepc, uepc),
+    //Ensure that the value of epc[0] is 0 at the root, rather than clearing it at the time of use
+    //MaskedRegMap(Uepc, uepc, wfn = (value: UInt) => (value & ~1.U(64.W))),
+
     // MaskedRegMap(Ucause, ucause),
     // MaskedRegMap(Utval, utval),
     // MaskedRegMap(Uip, uip),
@@ -411,7 +413,9 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
 
     // Supervisor Trap Handling
     MaskedRegMap(Sscratch, sscratch),
-    MaskedRegMap(Sepc, sepc),
+    //Ensure that the value of epc[0] is 0 at the root, rather than clearing it at the time of use
+    MaskedRegMap(Sepc, sepc, wfn = (value: UInt) => (value & ~1.U(64.W))),
+
     MaskedRegMap(Scause, scause),
     MaskedRegMap(Stval, stval),
     MaskedRegMap(Sip, mip.asUInt, sipMask, MaskedRegMap.Unwritable, sipMask),
@@ -437,7 +441,10 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
 
     // Machine Trap Handling
     MaskedRegMap(Mscratch, mscratch),
-    MaskedRegMap(Mepc, mepc),
+    //MaskedRegMap(Mepc, mepc),
+    //Ensure that the value of epc[0] is 0 at the root, rather than clearing it at the time of use
+    MaskedRegMap(Mepc, mepc, wfn = (value: UInt) => (value & ~1.U(64.W))),
+
     MaskedRegMap(Mcause, mcause),
     MaskedRegMap(Mtval, mtval),
     MaskedRegMap(Mip, mip.asUInt, 0.U, MaskedRegMap.Unwritable),
@@ -654,6 +661,7 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
 
   ret := isMret || isSret || isUret
   trapTarget := Mux(delegS, stvec, mtvec)(VAddrBits-1, 0)
+  
   retTarget := DontCare
   // TODO redirect target
   // val illegalEret = TODO
@@ -668,7 +676,7 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
     mstatusNew.mpp := ModeU
     mstatus := mstatusNew.asUInt
     lr := false.B
-    retTarget := mepc(VAddrBits-1, 0)
+    retTarget := mepc
   }
 
   when (valid && isSret) {
@@ -681,7 +689,7 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
     mstatusNew.spp := ModeU
     mstatus := mstatusNew.asUInt
     lr := false.B
-    retTarget := sepc(VAddrBits-1, 0)
+    retTarget := sepc
   }
 
   when (valid && isUret) {
@@ -692,7 +700,7 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
     priviledgeMode := ModeU
     mstatusNew.pie.u := true.B
     mstatus := mstatusNew.asUInt
-    retTarget := uepc(VAddrBits-1, 0)
+    retTarget := uepc
   }
 
   when (raiseExceptionIntr) {
@@ -946,3 +954,4 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
     }
   }
 }
+

From 30fa1ca8e3ebe5ef33b13b6579d449a4b28937cd Mon Sep 17 00:00:00 2001
From: =youzi27 <=809891392@qq.com>
Date: Wed, 6 Dec 2023 13:39:39 +0800
Subject: [PATCH 2/2] Fix:epc[0] value is always 0

---
 src/main/scala/nutcore/backend/fu/CSR.scala | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/main/scala/nutcore/backend/fu/CSR.scala b/src/main/scala/nutcore/backend/fu/CSR.scala
index 46bd3bb1..5071af6d 100644
--- a/src/main/scala/nutcore/backend/fu/CSR.scala
+++ b/src/main/scala/nutcore/backend/fu/CSR.scala
@@ -661,7 +661,6 @@ class CSR(implicit val p: NutCoreConfig) extends NutCoreModule with HasCSRConst{
 
   ret := isMret || isSret || isUret
   trapTarget := Mux(delegS, stvec, mtvec)(VAddrBits-1, 0)
-  
   retTarget := DontCare
   // TODO redirect target
   // val illegalEret = TODO