riscv{32,64},exec: reset gpr[0] after every instruction

src/isa/riscv32/exec/exec.c

@@ -90,5 +90,9 @@ vaddr_t isa_exec_once() {
   void query_intr(DecodeExecState *s);
   query_intr(&s);
 #endif
+
+  // reset gpr[0]
+  reg_l(0) = 0;
+
   return s.seq_pc;
 }

src/isa/riscv32/local-include/decode.h

@@ -16,7 +16,6 @@ static inline make_DopHelper(r) {
   op->type = OP_TYPE_REG;
   op->reg = val;
   op->preg = &reg_l(val);
-  reg_l(0) = 0;
 
   print_Dop(op->str, OP_STR_SIZE, "%s", reg_name(op->reg, 4));
 }

src/isa/riscv64/exec/exec.c

@@ -226,5 +226,9 @@ vaddr_t isa_exec_once() {
   void query_intr(DecodeExecState *s);
   query_intr(&s);
 #endif
+
+  // reset gpr[0]
+  reg_l(0) = 0;
+
   return s.seq_pc;
 }

src/isa/riscv64/local-include/decode.h

@@ -16,7 +16,6 @@ static inline make_DopHelper(r) {
   op->type = OP_TYPE_REG;
   op->reg = val;
   op->preg = &reg_l(val);
-  reg_l(0) = 0;
 
   print_Dop(op->str, OP_STR_SIZE, "%s", reg_name(op->reg, 4));
 }