target/arm: Convert T16 branch and exchange

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190904193059.26202-54-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 39 insertions, 41 deletions

diff --git a/target/arm/t16.decode b/target/arm/t16.decode
index 0654275e68..edddbfb9b8 100644
--- a/target/arm/t16.decode
+++ b/target/arm/t16.decode
@@ -24,6 +24,7 @@
 &s_rri_rot       !extern s rn rd imm rot
 &s_rrrr          !extern s rd rn rm ra
 &ri              !extern rd imm
+&r               !extern rm
 &ldst_rr         !extern p w u rn rt rm shimm shtype
 &ldst_ri         !extern p w u rn rt imm
 &ldst_block      !extern rn i b u w list
@@ -144,3 +145,12 @@ MOV_rxi         00100 ... ........              @arith_1i %s
 CMP_xri         00101 ... ........              @arith_1i s=1
 ADD_rri         00110 ... ........              @arith_1i %s
 SUB_rri         00111 ... ........              @arith_1i %s
+
+# Branch and exchange
+
+@branchr        .... .... . rm:4 ...            &r
+
+BX              0100 0111 0 .... 000            @branchr
+BLX_r           0100 0111 1 .... 000            @branchr
+BXNS            0100 0111 0 .... 100            @branchr
+BLXNS           0100 0111 1 .... 100            @branchr
diff --git a/target/arm/translate.c b/target/arm/translate.c
index 405176527c..e6ef935247 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -8364,7 +8364,7 @@ static bool trans_BX(DisasContext *s, arg_BX *a)
     if (!ENABLE_ARCH_4T) {
         return false;
     }
-    gen_bx(s, load_reg(s, a->rm));
+    gen_bx_excret(s, load_reg(s, a->rm));
     return true;
 }
 
@@ -8391,6 +8391,32 @@ static bool trans_BLX_r(DisasContext *s, arg_BLX_r *a)
     return true;
 }
 
+/*
+ * BXNS/BLXNS: only exist for v8M with the security extensions,
+ * and always UNDEF if NonSecure.  We don't implement these in
+ * the user-only mode either (in theory you can use them from
+ * Secure User mode but they are too tied in to system emulation).
+ */
+static bool trans_BXNS(DisasContext *s, arg_BXNS *a)
+{
+    if (!s->v8m_secure || IS_USER_ONLY) {
+        unallocated_encoding(s);
+    } else {
+        gen_bxns(s, a->rm);
+    }
+    return true;
+}
+
+static bool trans_BLXNS(DisasContext *s, arg_BLXNS *a)
+{
+    if (!s->v8m_secure || IS_USER_ONLY) {
+        unallocated_encoding(s);
+    } else {
+        gen_blxns(s, a->rm);
+    }
+    return true;
+}
+
 static bool trans_CLZ(DisasContext *s, arg_CLZ *a)
 {
     TCGv_i32 tmp;
@@ -10756,49 +10782,11 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn)
                 }
                 break;
             case 3:
-            {
                 /* 0b0100_0111_xxxx_xxxx
                  * - branch [and link] exchange thumb register
+                 * In decodetree
                  */
-                bool link = insn & (1 << 7);
-
-                if (insn & 3) {
-                    goto undef;
-                }
-                if (link) {
-                    ARCH(5);
-                }
-                if ((insn & 4)) {
-                    /* BXNS/BLXNS: only exists for v8M with the
-                     * security extensions, and always UNDEF if NonSecure.
-                     * We don't implement these in the user-only mode
-                     * either (in theory you can use them from Secure User
-                     * mode but they are too tied in to system emulation.)
-                     */
-                    if (!s->v8m_secure || IS_USER_ONLY) {
-                        goto undef;
-                    }
-                    if (link) {
-                        gen_blxns(s, rm);
-                    } else {
-                        gen_bxns(s, rm);
-                    }
-                    break;
-                }
-                /* BLX/BX */
-                tmp = load_reg(s, rm);
-                if (link) {
-                    val = (uint32_t)s->base.pc_next | 1;
-                    tmp2 = tcg_temp_new_i32();
-                    tcg_gen_movi_i32(tmp2, val);
-                    store_reg(s, 14, tmp2);
-                    gen_bx(s, tmp);
-                } else {
-                    /* Only BX works as exception-return, not BLX */
-                    gen_bx_excret(s, tmp);
-                }
-                break;
-            }
+                goto illegal_op;
             }
             break;
         }