[PULL 6/7] target/arm: Relax r13 restriction for ldrex/strex for v8.0

[Peter Maydell <peter.maydell@linaro.org>]

From: Richard Henderson <richard.henderson@linaro.org>

Armv8-A removes UNPREDICTABLE for R13 for these cases.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20191117090621.32425-3-richard.henderson@linaro.org
[PMM: changed ENABLE_ARCH_8 checks to check a new bool 'v8a',
 since these cases are still UNPREDICTABLE for v8M]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/translate.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/target/arm/translate.c b/target/arm/translate.c
index b285b23858e..4d5d4bd8886 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -8927,15 +8927,17 @@ static bool trans_SWPB(DisasContext *s, arg_SWP *a)
 static bool op_strex(DisasContext *s, arg_STREX *a, MemOp mop, bool rel)
 {
     TCGv_i32 addr;
+    /* Some cases stopped being UNPREDICTABLE in v8A (but not v8M) */
+    bool v8a = ENABLE_ARCH_8 && !arm_dc_feature(s, ARM_FEATURE_M);
 
     /* We UNDEF for these UNPREDICTABLE cases.  */
     if (a->rd == 15 || a->rn == 15 || a->rt == 15
         || a->rd == a->rn || a->rd == a->rt
-        || (s->thumb && (a->rd == 13 || a->rt == 13))
+        || (!v8a && s->thumb && (a->rd == 13 || a->rt == 13))
         || (mop == MO_64
             && (a->rt2 == 15
                 || a->rd == a->rt2
-                || (s->thumb && a->rt2 == 13)))) {
+                || (!v8a && s->thumb && a->rt2 == 13)))) {
         unallocated_encoding(s);
         return true;
     }
@@ -9084,13 +9086,15 @@ static bool trans_STLH(DisasContext *s, arg_STL *a)
 static bool op_ldrex(DisasContext *s, arg_LDREX *a, MemOp mop, bool acq)
 {
     TCGv_i32 addr;
+    /* Some cases stopped being UNPREDICTABLE in v8A (but not v8M) */
+    bool v8a = ENABLE_ARCH_8 && !arm_dc_feature(s, ARM_FEATURE_M);
 
     /* We UNDEF for these UNPREDICTABLE cases.  */
     if (a->rn == 15 || a->rt == 15
-        || (s->thumb && a->rt == 13)
+        || (!v8a && s->thumb && a->rt == 13)
         || (mop == MO_64
             && (a->rt2 == 15 || a->rt == a->rt2
-                || (s->thumb && a->rt2 == 13)))) {
+                || (!v8a && s->thumb && a->rt2 == 13)))) {
         unallocated_encoding(s);
         return true;
     }
-- 
2.20.1