target/arm: Diagnose base == pc for LDM/STM

We have been using store_reg and not store_reg_for_load when writing
back a loaded value into the base register.  At first glance this is
incorrect when base == pc, however that case is UNPREDICTABLE.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190904193059.26202-32-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/target/arm/translate.c b/target/arm/translate.c
index b623dbcd481644b8c15d186d805e773b0e4d9b46..d0fc916ff9918c113eaa7b2a97e3fe61216b2403 100644 (file)
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -9863,7 +9863,7 @@ static bool op_stm(DisasContext *s, arg_ldst_block *a, int min_n)
 
     list = a->list;
     n = ctpop16(list);
-    if (n < min_n) {
+    if (n < min_n || a->rn == 15) {
         unallocated_encoding(s);
         return true;
     }
@@ -9943,7 +9943,7 @@ static bool do_ldm(DisasContext *s, arg_ldst_block *a, int min_n)
 
     list = a->list;
     n = ctpop16(list);
-    if (n < min_n) {
+    if (n < min_n || a->rn == 15) {
         unallocated_encoding(s);
         return true;
     }
@@ -9983,6 +9983,7 @@ static bool do_ldm(DisasContext *s, arg_ldst_block *a, int min_n)
     op_addr_block_post(s, a, addr, n);
 
     if (loaded_base) {
+        /* Note that we reject base == pc above.  */
         store_reg(s, a->rn, loaded_var);
     }