target/nios2: Advance pc when raising exceptions

The exception return address for nios2 is the instruction
after the one that was executing at the time of the exception.

We have so far implemented this by advancing the pc during the
process of raising the exception.  It is perhaps a little less
confusing to do this advance in the translator (and helpers)
when raising the exception in the first place, so that we may
more closely match kernel sources.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220421151735.31996-58-richard.henderson@linaro.org>

linux-user/nios2/cpu_loop.c

@@ -39,6 +39,8 @@ void cpu_loop(CPUNios2State *env)
             break;
 
         case EXCP_DIV:
+            /* Match kernel's handle_diverror_c(). */
+            env->pc -= 4;
             force_sig_fault(TARGET_SIGFPE, TARGET_FPE_INTDIV, env->pc);
             break;
 
@@ -49,12 +51,6 @@ void cpu_loop(CPUNios2State *env)
             break;
 
         case EXCP_TRAP:
-            /*
-             * TODO: This advance should be done in the translator, as
-             * hardware produces an advanced pc as part of all exceptions.
-             */
-            env->pc += 4;
-
             switch (env->error_code) {
             case 0:
                 qemu_log_mask(CPU_LOG_INT, "\nSyscall\n");