target/microblaze: Unwind properly when raising divide-by-zero

Restore the correct pc when raising divide-by-zero.  Also, the
MSR[DZO] bit is sticky -- it is not cleared with a successful divide.

Tested-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 14 insertions, 13 deletions

diff --git a/target/microblaze/helper.h b/target/microblaze/helper.h
index 6f7f96421f..79e1e8ecc7 100644
--- a/target/microblaze/helper.h
+++ b/target/microblaze/helper.h
@@ -1,7 +1,7 @@
 DEF_HELPER_FLAGS_2(raise_exception, TCG_CALL_NO_WG, noreturn, env, i32)
 
-DEF_HELPER_3(divs, i32, env, i32, i32)
-DEF_HELPER_3(divu, i32, env, i32, i32)
+DEF_HELPER_FLAGS_3(divs, TCG_CALL_NO_WG, i32, env, i32, i32)
+DEF_HELPER_FLAGS_3(divu, TCG_CALL_NO_WG, i32, env, i32, i32)
 
 DEF_HELPER_3(fadd, i32, env, i32, i32)
 DEF_HELPER_3(frsub, i32, env, i32, i32)
diff --git a/target/microblaze/op_helper.c b/target/microblaze/op_helper.c
index f976d112eb..d99d98051a 100644
--- a/target/microblaze/op_helper.c
+++ b/target/microblaze/op_helper.c
@@ -69,26 +69,27 @@ void helper_raise_exception(CPUMBState *env, uint32_t index)
     cpu_loop_exit(cs);
 }
 
-static inline int div_prepare(CPUMBState *env, uint32_t a, uint32_t b)
+static bool check_divz(CPUMBState *env, uint32_t a, uint32_t b, uintptr_t ra)
 {
-    MicroBlazeCPU *cpu = env_archcpu(env);
-
-    if (b == 0) {
+    if (unlikely(b == 0)) {
         env->msr |= MSR_DZ;
 
-        if ((env->msr & MSR_EE) && cpu->cfg.div_zero_exception) {
+        if ((env->msr & MSR_EE) &&
+            env_archcpu(env)->cfg.div_zero_exception) {
+            CPUState *cs = env_cpu(env);
+
             env->esr = ESR_EC_DIVZERO;
-            helper_raise_exception(env, EXCP_HW_EXCP);
+            cs->exception_index = EXCP_HW_EXCP;
+            cpu_loop_exit_restore(cs, ra);
         }
-        return 0;
+        return false;
     }
-    env->msr &= ~MSR_DZ;
-    return 1;
+    return true;
 }
 
 uint32_t helper_divs(CPUMBState *env, uint32_t a, uint32_t b)
 {
-    if (!div_prepare(env, a, b)) {
+    if (!check_divz(env, a, b, GETPC())) {
         return 0;
     }
     return (int32_t)a / (int32_t)b;
@@ -96,7 +97,7 @@ uint32_t helper_divs(CPUMBState *env, uint32_t a, uint32_t b)
 
 uint32_t helper_divu(CPUMBState *env, uint32_t a, uint32_t b)
 {
-    if (!div_prepare(env, a, b)) {
+    if (!check_divz(env, a, b, GETPC())) {
         return 0;
     }
     return a / b;