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Re: [PATCH] op_helper: fix some compile warnings
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From: |
Pan Nengyuan |
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Subject: |
Re: [PATCH] op_helper: fix some compile warnings |
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Date: |
Mon, 20 Apr 2020 19:04:40 +0800 |
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User-agent: |
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 |
On 4/20/2020 5:49 PM, Yoshinori Sato wrote:
> On Mon, 20 Apr 2020 18:18:39 +0900,
> Pan Nengyuan wrote:
>>
>>
>>
>> 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 <address@hidden>
>>>> Signed-off-by: Pan Nengyuan <address@hidden>
>>>> ---
>>>> 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.
>
> Oh. Sorry. I misunderstood.
>
> Since the pseudo code described in the manual uses while,
> I think it's easier for everyone to understand by following
> the description.
>
>>> 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.
Oh, I'm sorry for my mistake, it can't disappear the warnings:
/mnt/sdb/qemu/target/rx/op_helper.c: In function ‘helper_scmpu’:
/mnt/sdb/qemu/target/rx/op_helper.c:211:28: 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:211:28: error: ‘tmp0’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]
CC ppc64abi32-linux-user/target/ppc/translate.o
CC ppc64le-linux-user/target/ppc/translate.o
CC ppc64-linux-user/target/ppc/translate.o
CC ppc-linux-user/target/ppc/translate.o
/mnt/sdb/qemu/target/rx/op_helper.c: In function ‘helper_suntil’:
/mnt/sdb/qemu/target/rx/op_helper.c:296:27: 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:314:27: error: ‘tmp’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]
env->psw_c = (tmp <= env->regs[2]);
~~~~~^~~~~~~~~~~~~~~~
If we want to use 'while' as the pseudo code described in the manual, can we
init the tmp variable at the beginning? like that:
uint32_t tmp = 0;
>
> OK. Thanks.
>
>> Thanks.
>>
>>> >From 5de0c54a970e01e96b41870252d0ea54ec61c540 Mon Sep 17 00:00:00 2001
>>> From: Yoshinori Sato <address@hidden>
>>> Date: Mon, 20 Apr 2020 17:41:04 +0900
>>> Subject: [PATCH] target/rx/op_helper: Fix uninitialized warning.
>>>
>>> Signed-off-by: Yoshinori Sato <address@hidden>
>>> ---
>>> 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)
>>>
>