target/nios2: Cleanup set of CR_EXCEPTION for do_interrupt

The register is entirely read-only for software, and we do not
implement ECC, so we need not deposit the cause into an existing
value; just create a new value from scratch.

Furthermore, exception.CAUSE is not written for break exceptions.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220421151735.31996-36-richard.henderson@linaro.org>

diff --git a/target/nios2/helper.c b/target/nios2/helper.c
index 25a8972..3d98694 100644 (file)
--- a/target/nios2/helper.c
+++ b/target/nios2/helper.c
@@ -54,9 +54,10 @@ static void do_exception(Nios2CPU *cpu, uint32_t exception_addr, bool is_break)
     new_status &= ~(CR_STATUS_PIE | CR_STATUS_U);
 
     env->ctrl[CR_STATUS] = new_status;
-    env->ctrl[CR_EXCEPTION] = FIELD_DP32(env->ctrl[CR_EXCEPTION],
-                                         CR_EXCEPTION, CAUSE,
-                                         cs->exception_index);
+    if (!is_break) {
+        env->ctrl[CR_EXCEPTION] = FIELD_DP32(0, CR_EXCEPTION, CAUSE,
+                                             cs->exception_index);
+    }
     env->pc = exception_addr;
 }