target/arm: Convert division from feature bits to isar0 tests

Both arm and thumb2 division are controlled by the same ISAR field,
which takes care of the arm implies thumb case.  Having M imply
thumb2 division was wrong for cortex-m0, which is v6m and does not
have thumb2 at all, much less thumb2 division.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181016223115.24100-5-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

linux-user/elfload.c

@@ -471,8 +471,8 @@ static uint32_t get_elf_hwcap(void)
     GET_FEATURE(ARM_FEATURE_VFP3, ARM_HWCAP_ARM_VFPv3);
     GET_FEATURE(ARM_FEATURE_V6K, ARM_HWCAP_ARM_TLS);
     GET_FEATURE(ARM_FEATURE_VFP4, ARM_HWCAP_ARM_VFPv4);
-    GET_FEATURE(ARM_FEATURE_ARM_DIV, ARM_HWCAP_ARM_IDIVA);
+    GET_FEATURE_ID(arm_div, ARM_HWCAP_ARM_IDIVA);
-    GET_FEATURE(ARM_FEATURE_THUMB_DIV, ARM_HWCAP_ARM_IDIVT);
+    GET_FEATURE_ID(thumb_div, ARM_HWCAP_ARM_IDIVT);
     /* All QEMU's VFPv3 CPUs have 32 registers, see VFP_DREG in translate.c.
      * Note that the ARM_HWCAP_ARM_VFPv3D16 bit is always the inverse of
      * ARM_HWCAP_ARM_VFPD32 (and so always clear for QEMU); it is unrelated

target/arm/cpu.c

@@ -829,7 +829,7 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
          * Presence of EL2 itself is ARM_FEATURE_EL2, and of the
          * Security Extensions is ARM_FEATURE_EL3.
          */
-        set_feature(env, ARM_FEATURE_ARM_DIV);
+        assert(cpu_isar_feature(arm_div, cpu));
         set_feature(env, ARM_FEATURE_LPAE);
         set_feature(env, ARM_FEATURE_V7);
     }
@@ -862,12 +862,6 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
     if (arm_feature(env, ARM_FEATURE_V5)) {
         set_feature(env, ARM_FEATURE_V4T);
     }
-    if (arm_feature(env, ARM_FEATURE_M)) {
-        set_feature(env, ARM_FEATURE_THUMB_DIV);
-    }
-    if (arm_feature(env, ARM_FEATURE_ARM_DIV)) {
-        set_feature(env, ARM_FEATURE_THUMB_DIV);
-    }
     if (arm_feature(env, ARM_FEATURE_VFP4)) {
         set_feature(env, ARM_FEATURE_VFP3);
         set_feature(env, ARM_FEATURE_VFP_FP16);
@@ -1388,8 +1382,6 @@ static void cortex_r5_initfn(Object *obj)
     ARMCPU *cpu = ARM_CPU(obj);
 
     set_feature(&cpu->env, ARM_FEATURE_V7);
-    set_feature(&cpu->env, ARM_FEATURE_THUMB_DIV);
-    set_feature(&cpu->env, ARM_FEATURE_ARM_DIV);
     set_feature(&cpu->env, ARM_FEATURE_V7MP);
     set_feature(&cpu->env, ARM_FEATURE_PMSA);
     cpu->midr = 0x411fc153; /* r1p3 */

target/arm/cpu.h

@@ -1563,7 +1563,6 @@ enum arm_features {
     ARM_FEATURE_VFP3,
     ARM_FEATURE_VFP_FP16,
     ARM_FEATURE_NEON,
-    ARM_FEATURE_THUMB_DIV, /* divide supported in Thumb encoding */
     ARM_FEATURE_M, /* Microcontroller profile.  */
     ARM_FEATURE_OMAPCP, /* OMAP specific CP15 ops handling.  */
     ARM_FEATURE_THUMB2EE,
@@ -1573,7 +1572,6 @@ enum arm_features {
     ARM_FEATURE_V5,
     ARM_FEATURE_STRONGARM,
     ARM_FEATURE_VAPA, /* cp15 VA to PA lookups */
-    ARM_FEATURE_ARM_DIV, /* divide supported in ARM encoding */
     ARM_FEATURE_VFP4, /* VFPv4 (implies that NEON is v2) */
     ARM_FEATURE_GENERIC_TIMER,
     ARM_FEATURE_MVFR, /* Media and VFP Feature Registers 0 and 1 */
@@ -3152,6 +3150,16 @@ extern const uint64_t pred_esz_masks[4];
 /*
  * 32-bit feature tests via id registers.
  */
+static inline bool isar_feature_thumb_div(const ARMISARegisters *id)
+{
+    return FIELD_EX32(id->id_isar0, ID_ISAR0, DIVIDE) != 0;
+}
+
+static inline bool isar_feature_arm_div(const ARMISARegisters *id)
+{
+    return FIELD_EX32(id->id_isar0, ID_ISAR0, DIVIDE) > 1;
+}
+
 static inline bool isar_feature_aa32_aes(const ARMISARegisters *id)
 {
     return FIELD_EX32(id->id_isar5, ID_ISAR5, AES) != 0;

target/arm/translate.c

@@ -9755,7 +9755,7 @@ static void disas_arm_insn(DisasContext *s, unsigned int insn)
                     case 1:
                     case 3:
                         /* SDIV, UDIV */
-                        if (!arm_dc_feature(s, ARM_FEATURE_ARM_DIV)) {
+                        if (!dc_isar_feature(arm_div, s)) {
                             goto illegal_op;
                         }
                         if (((insn >> 5) & 7) || (rd != 15)) {
@@ -10963,7 +10963,7 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
             tmp2 = load_reg(s, rm);
             if ((op & 0x50) == 0x10) {
                 /* sdiv, udiv */
-                if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DIV)) {
+                if (!dc_isar_feature(thumb_div, s)) {
                     goto illegal_op;
                 }
                 if (op & 0x20)