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Re: [PATCH] op_helper: fix some compile warnings
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From: |
Yoshinori Sato |
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Subject: |
Re: [PATCH] op_helper: fix some compile warnings |
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Date: |
Mon, 20 Apr 2020 18:49:14 +0900 |
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User-agent: |
Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (Gojō) APEL/10.8 EasyPG/1.0.0 Emacs/26 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) |
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.
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)
> >
--
Yosinori Sato