diff --git a/src/isa/mips32/exec/system.c b/src/isa/mips32/exec/system.c
index 99b70516d2a6881a631e4e0be638e46a07b18fd6..3dbda51de90bdc38ab41e87065b3a4bfc093545e 100644
--- a/src/isa/mips32/exec/system.c
+++ b/src/isa/mips32/exec/system.c
@@ -30,18 +30,16 @@ make_EHelper(mfc0) {
 #endif
 
   uint32_t val;
-  char *name;
   switch (id_dest->reg) {
-    case 12: val = cpu.status; name = "status"; break;
-    case 13: val = cpu.cause; name = "cause"; break;
-    case 14: val = cpu.epc; name = "epc"; break;
+    case 12: val = cpu.status; print_asm("mfc0 %s, status", id_src2->str); break;
+    case 13: val = cpu.cause; print_asm("mfc0 %s, cause", id_src2->str); break;
+    case 14: val = cpu.epc; print_asm("mfc0 %s, epc", id_src2->str); break;
     default: assert(0);
   }
 
   rtl_li(&s0, val);
   rtl_sr(id_src2->reg, &s0, 4);
 
-  print_asm("mfc0 %s, %s", id_src2->str, name);
 }
 
 make_EHelper(mtc0) {
@@ -49,13 +47,11 @@ make_EHelper(mtc0) {
   difftest_skip_ref();
 #endif
 
-  char *name;
   switch (id_dest->reg) {
-    case 12: cpu.status = id_src2->val; name = "status"; break;
-    case 13: cpu.cause = id_src2->val; name = "cause"; break;
-    case 14: cpu.epc = id_src2->val; name = "epc"; break;
+    case 12: cpu.status = id_src2->val; print_asm("mtc0 %s, status", id_src2->str); break;
+    case 13: cpu.cause = id_src2->val; print_asm("mtc0 %s, cause", id_src2->str); break;
+    case 14: cpu.epc = id_src2->val; print_asm("mtc0 %s, epc", id_src2->str); break;
     default: assert(0);
   }
 
-  print_asm("mtc0 %s, %s", id_src2->str, name);
 }
diff --git a/src/monitor/cpu-exec.c b/src/monitor/cpu-exec.c
index 3269b19efa05282cccf29658965c39177a65c734..31321096f2b8f7afc56fce2d5613d45bfaec75eb 100644
--- a/src/monitor/cpu-exec.c
+++ b/src/monitor/cpu-exec.c
@@ -1,5 +1,6 @@
 #include "nemu.h"
 #include "monitor/monitor.h"
+#include "monitor/watchpoint.h"
 
 /* The assembly code of instructions executed is only output to the screen
  * when the number of instructions executed is less than this value.
@@ -37,6 +38,9 @@ void cpu_exec(uint64_t n) {
   bool print_flag = n < MAX_INSTR_TO_PRINT;
 
   for (; n > 0; n --) {
+#ifdef DEBUG
+    vaddr_t temp_pc = cpu.pc;
+#endif
     /* Execute one instruction, including instruction fetch,
      * instruction decode, and the actual execution. */
     exec_wrapper(print_flag);
@@ -44,6 +48,13 @@ void cpu_exec(uint64_t n) {
 
 #ifdef DEBUG
     /* TODO: check watchpoints here. */
+    WP *wp = scan_watchpoint();
+    if(wp != NULL) {
+      printf("\n\nHint watchpoint %d at address 0x%08x, expr = %s\n", wp->NO, temp_pc, wp->expr);
+      printf("old value = %#08x\nnew value = %#08x\n", wp->old_val, wp->new_val);
+      wp->old_val = wp->new_val;
+      return;
+    }
 
 #endif
 
diff --git a/src/monitor/debug/expr.c b/src/monitor/debug/expr.c
index 24eb9172e394fbe6a92f1cd4b7b7dcdccbfe98ec..2a9d0de7df8fc6a9381faf47c57cbe8fc0fba6cd 100644
--- a/src/monitor/debug/expr.c
+++ b/src/monitor/debug/expr.c
@@ -87,8 +87,8 @@ static bool make_token(char *e) {
         char *substr_start = e + position;
         int substr_len = pmatch.rm_eo;
 
-        Log("match rules[%d] = \"%s\" at position %d with len %d: %.*s",
-            i, rules[i].regex, position, substr_len, substr_len, substr_start);
+        //Log("match rules[%d] = \"%s\" at position %d with len %d: %.*s",
+        //    i, rules[i].regex, position, substr_len, substr_len, substr_start);
 
         position += substr_len;
 
diff --git a/src/monitor/diff-test/diff-test.c b/src/monitor/diff-test/diff-test.c
index 72fc521d7db05fcd9155b6622faa568967390752..7343d3e0ca66d2e2aa2a89cfdd0da27d303a5b94 100644
--- a/src/monitor/diff-test/diff-test.c
+++ b/src/monitor/diff-test/diff-test.c
@@ -79,6 +79,8 @@ void difftest_step(vaddr_t pc) {
 
   // TODO: Check the registers state with QEMU.
   if (!isa_difftest_checkregs(&ref_r, pc)) {
+    extern void isa_reg_display(void);
+    isa_reg_display();
     nemu_state.state = NEMU_ABORT;
     nemu_state.halt_pc = pc;
   }