On 4/20/2020 4:50 PM, Yoshinori Sato wrote:
> On Mon, 20 Apr 2020 14:49:59 +0900,
> Pan Nengyuan wrote:
>>
>> We got the following compile-time warnings(gcc7.3):
>> /mnt/sdb//qemu/target/rx/op_helper.c: In function ‘helper_scmpu’:
>> /mnt/sdb/qemu/target/rx/op_helper.c:213:24: error: ‘tmp1’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>> env->psw_c = (tmp0 >= tmp1);
>> ~~~~~~^~~~~~~~
>> /mnt/sdb/qemu/target/rx/op_helper.c:213:24: error: ‘tmp0’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>> /mnt/sdb/qemu/target/rx/op_helper.c: In function ‘helper_suntil’:
>> /mnt/sdb/qemu/target/rx/op_helper.c:299:23: error: ‘tmp’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>> env->psw_c = (tmp <= env->regs[2]);
>> ~~~~~^~~~~~~~~~~~~~~~
>> /mnt/sdb/qemu/target/rx/op_helper.c: In function ‘helper_swhile’:
>> /mnt/sdb/qemu/target/rx/op_helper.c:318:23: error: ‘tmp’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>> env->psw_c = (tmp <= env->regs[2]);
>>
>> Actually, it looks like a false-positive because it will enter the body of
>> while loop and init it for the first time.
>> Let's change 'while' to 'do .. while' to avoid it.
>
> OK.
>
>> Reported-by: Euler Robot <euler.ro...@huawei.com>
>> Signed-off-by: Pan Nengyuan <pannengy...@huawei.com>
>> ---
>> target/rx/op_helper.c | 12 ++++++------
>> 1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/target/rx/op_helper.c b/target/rx/op_helper.c
>> index f89d294f2b..b612ab1da8 100644
>> --- a/target/rx/op_helper.c
>> +++ b/target/rx/op_helper.c
>> @@ -201,14 +201,14 @@ void helper_scmpu(CPURXState *env)
>> if (env->regs[3] == 0) {
>> return;
>> }
>> - while (env->regs[3] != 0) {
>> + do {
>> tmp0 = cpu_ldub_data_ra(env, env->regs[1]++, GETPC());
>> tmp1 = cpu_ldub_data_ra(env, env->regs[2]++, GETPC());
>> env->regs[3]--;
>> if (tmp0 != tmp1 || tmp0 == '\0') {
>> break;
>> }
>> - }
>> + } while (env->regs[3] != 0);
>> env->psw_z = tmp0 - tmp1;
>> env->psw_c = (tmp0 >= tmp1);
>> }
>> @@ -287,14 +287,14 @@ void helper_suntil(CPURXState *env, uint32_t sz)
>> if (env->regs[3] == 0) {
>> return ;
>> }
>> - while (env->regs[3] != 0) {
>> + do {
>> tmp = cpu_ldufn[sz](env, env->regs[1], GETPC());
>> env->regs[1] += 1 << sz;
>> env->regs[3]--;
>> if (tmp == env->regs[2]) {
>> break;
>> }
>> - }
>> + } while (env->regs[3] != 0);
>> env->psw_z = tmp - env->regs[2];
>> env->psw_c = (tmp <= env->regs[2]);
>> }
>> @@ -306,14 +306,14 @@ void helper_swhile(CPURXState *env, uint32_t sz)
>> if (env->regs[3] == 0) {
>> return ;
>> }
>> - while (env->regs[3] != 0) {
>> + do {
>> tmp = cpu_ldufn[sz](env, env->regs[1], GETPC());
>> env->regs[1] += 1 << sz;
>> env->regs[3]--;
>> if (tmp != env->regs[2]) {
>> break;
>> }
>> - }
>> + } while (env->regs[3] != 0);
>> env->psw_z = env->regs[3];
>> env->psw_c = (tmp <= env->regs[2]);
>> }
>> --
>> 2.18.2
>>
>>
>
> It looks different result in env->regs[3] is zero.
If env->regs[3] is zero, it will return at the begin of these functions:
if (env->regs[3] == 0) {
return;
}
Thus, the while loop will not be reached.
In this case, I think 'while' and 'do .. while' will get the same result and it
will disappear the warnings.
> In such a case, nothing changes.
>
> I think that the warning of the uninitialized variable
> will disappear by fixing as follows.
>
Yes, it also can fix these warnings.
Thanks.
>>From 5de0c54a970e01e96b41870252d0ea54ec61c540 Mon Sep 17 00:00:00 2001
> From: Yoshinori Sato <ys...@users.sourceforge.jp>
> Date: Mon, 20 Apr 2020 17:41:04 +0900
> Subject: [PATCH] target/rx/op_helper: Fix uninitialized warning.
>
> Signed-off-by: Yoshinori Sato <ys...@users.sourceforge.jp>
> ---
> target/rx/op_helper.c | 101 ++++++++++++++++++++----------------------
> 1 file changed, 49 insertions(+), 52 deletions(-)
>
> diff --git a/target/rx/op_helper.c b/target/rx/op_helper.c
> index f89d294f2b..f84f6c706c 100644
> --- a/target/rx/op_helper.c
> +++ b/target/rx/op_helper.c
> @@ -284,38 +284,36 @@ void helper_suntil(CPURXState *env, uint32_t sz)
> {
> uint32_t tmp;
> tcg_debug_assert(sz < 3);
> - if (env->regs[3] == 0) {
> - return ;
> - }
> - while (env->regs[3] != 0) {
> - tmp = cpu_ldufn[sz](env, env->regs[1], GETPC());
> - env->regs[1] += 1 << sz;
> - env->regs[3]--;
> - if (tmp == env->regs[2]) {
> - break;
> + if (env->regs[3] > 0) {
> + while (env->regs[3] != 0) {
> + tmp = cpu_ldufn[sz](env, env->regs[1], GETPC());
> + env->regs[1] += 1 << sz;
> + env->regs[3]--;
> + if (tmp == env->regs[2]) {
> + break;
> + }
> }
> + env->psw_z = tmp - env->regs[2];
> + env->psw_c = (tmp <= env->regs[2]);
> }
> - env->psw_z = tmp - env->regs[2];
> - env->psw_c = (tmp <= env->regs[2]);
> }
>
> void helper_swhile(CPURXState *env, uint32_t sz)
> {
> uint32_t tmp;
> tcg_debug_assert(sz < 3);
> - if (env->regs[3] == 0) {
> - return ;
> - }
> - while (env->regs[3] != 0) {
> - tmp = cpu_ldufn[sz](env, env->regs[1], GETPC());
> - env->regs[1] += 1 << sz;
> - env->regs[3]--;
> - if (tmp != env->regs[2]) {
> - break;
> + if (env->regs[3] > 0) {
> + while (env->regs[3] != 0) {
> + tmp = cpu_ldufn[sz](env, env->regs[1], GETPC());
> + env->regs[1] += 1 << sz;
> + env->regs[3]--;
> + if (tmp != env->regs[2]) {
> + break;
> + }
> }
> + env->psw_z = env->regs[3];
> + env->psw_c = (tmp <= env->regs[2]);
> }
> - env->psw_z = env->regs[3];
> - env->psw_c = (tmp <= env->regs[2]);
> }
>
> /* accumlator operations */
> @@ -325,40 +323,39 @@ void helper_rmpa(CPURXState *env, uint32_t sz)
> int32_t result_h;
> int64_t tmp0, tmp1;
>
> - if (env->regs[3] == 0) {
> - return;
> - }
> - result_l = env->regs[5];
> - result_l <<= 32;
> - result_l |= env->regs[4];
> - result_h = env->regs[6];
> - env->psw_o = 0;
> + if (env->regs[3] > 0) {
> + result_l = env->regs[5];
> + result_l <<= 32;
> + result_l |= env->regs[4];
> + result_h = env->regs[6];
> + env->psw_o = 0;
>
> - while (env->regs[3] != 0) {
> - tmp0 = cpu_ldfn[sz](env, env->regs[1], GETPC());
> - tmp1 = cpu_ldfn[sz](env, env->regs[2], GETPC());
> - tmp0 *= tmp1;
> - prev = result_l;
> - result_l += tmp0;
> - /* carry / bollow */
> - if (tmp0 < 0) {
> - if (prev > result_l) {
> - result_h--;
> - }
> - } else {
> - if (prev < result_l) {
> - result_h++;
> + while (env->regs[3] != 0) {
> + tmp0 = cpu_ldfn[sz](env, env->regs[1], GETPC());
> + tmp1 = cpu_ldfn[sz](env, env->regs[2], GETPC());
> + tmp0 *= tmp1;
> + prev = result_l;
> + result_l += tmp0;
> + /* carry / bollow */
> + if (tmp0 < 0) {
> + if (prev > result_l) {
> + result_h--;
> + }
> + } else {
> + if (prev < result_l) {
> + result_h++;
> + }
> }
> - }
>
> - env->regs[1] += 1 << sz;
> - env->regs[2] += 1 << sz;
> + env->regs[1] += 1 << sz;
> + env->regs[2] += 1 << sz;
> + }
> + env->psw_s = result_h;
> + env->psw_o = (result_h != 0 && result_h != -1) << 31;
> + env->regs[6] = result_h;
> + env->regs[5] = result_l >> 32;
> + env->regs[4] = result_l & 0xffffffff;
> }
> - env->psw_s = result_h;
> - env->psw_o = (result_h != 0 && result_h != -1) << 31;
> - env->regs[6] = result_h;
> - env->regs[5] = result_l >> 32;
> - env->regs[4] = result_l & 0xffffffff;
> }
>
> void helper_racw(CPURXState *env, uint32_t imm)
>
