[Bug bootstrap/34592] New: useless computation found

[Bug bootstrap/34592] New: useless computation found

[dcb314 at hotmail dot com]

I just tried to bootstrap the GNU C compiler 4.3 snapshot
20071221 with the most excellent Intel C compiler version 10.1

The Intel compiler said

1.

gcc-4.3-20071221/fixincludes/fixincl.c(1049): remark #593: variable "name_len"
was set but never used

I had a look at the source code and I agree with the compiler.
Suggest delete local variable name_len.

2.

gcc-4.3-20071221/libdecnumber/decNumber.c(7406): remark #593: variable "dnexp"
was set but never used

I had a look at the source code and I agree with the compiler.
Suggest delete local variable dnexp.

3.

gcc-4.3-20071221/gcc/c-decl.c(4701): remark #593: variable "type_as_written"
was set but never used
gcc-4.3-20071221/gcc/c-decl.c(3977): remark #593: variable "typedef_type" was
set but never used

More of the same. Suggest delete local variables type_as_written and
typedef_type.


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           Summary: useless computation found
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: bootstrap
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dcb314 at hotmail dot com
  GCC host triplet: x86_64-suse-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34592

[Bug bootstrap/34592] useless computation found

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-12-26 14:01 -------
I always hated this warning from the EDG front-end, it sometimes produces a
false warning.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34592

[Bug other/34592] useless computation found

[dcb314 at hotmail dot com]

------- Comment #2 from dcb314 at hotmail dot com  2008-01-03 21:51 -------
Created an attachment (id=14871)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14871&action=view)
patch for gcc 4.3 20071228


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34592

[Bug other/34592] useless computation found

[dcb314 at hotmail dot com]

------- Comment #3 from dcb314 at hotmail dot com  2008-01-03 21:52 -------
(In reply to comment #1)
> I always hated this warning from the EDG front-end, it sometimes produces a
> false warning.

Feel free to send a bug report to EDG. 

Like I said, I checked each one and I agree with Intel C 10.1

I also counted about 300 similar cases where Intel
produced warning #593. I think there is quite a bit
of pointless computation going on.

I attach a patch again 4.3 snapshot 20071228.

Hint: Perhaps if this patch gets into 4.3 it would encourage
me to look at the other 300 cases ?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34592

[Bug other/34592] useless computation found

[aldot at gcc dot gnu dot org]

------- Comment #4 from aldot at gcc dot gnu dot org  2008-01-04 09:15 -------
I'd say that this is blocked by PR18624 (resp. PR30438 for fortran).

dcb, you seem to report these as separate PRs. Previous of this category
include:
PR25547
PR25567
PR26245
PR32948


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aldot at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aldot at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34592

[Bug other/34592] useless computation found

[dcb314 at hotmail dot com]

------- Comment #5 from dcb314 at hotmail dot com  2008-01-04 18:33 -------
(In reply to comment #4)
> I'd say that this is blocked by PR18624 (resp. PR30438 for fortran).
> dcb, you seem to report these as separate PRs. Previous of this category
> include:
> PR25547
> PR25567
> PR26245
> PR32948

I agree I have been reporting this bug for a couple of years.
I have even supplied patches. They have not been applied.

Cleaning up the compiler source code is one thing,
implementing a warning for the users is another.

I don't think putting them together helps.

Mind you, any progress on this issue would be welcome.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34592

[Bug other/34592] useless computation found

[manu at gcc dot gnu dot org]

------- Comment #6 from manu at gcc dot gnu dot org  2008-01-08 17:26 -------
(In reply to comment #3)
> 
> I also counted about 300 similar cases where Intel
> produced warning #593. I think there is quite a bit
> of pointless computation going on.
> 

Thanks. I think optimisers should remove all of them so they should not have
any effect. Nonetheless, if they are not really used, they should be removed
from the code.

> I attach a patch again 4.3 snapshot 20071228.

Unfortunately, GCC 4.3 is open only for regression and documentation fixes.
Your patch would need to wait for GCC 4.4. Yet, you can submit it right now and
there are chances that someone will review. To avoid conflicts between
maintainer of different parts of the compiler, I would suggest one different
submission per component (or if you cannot distinguish the components, one
submission per file).

> Hint: Perhaps if this patch gets into 4.3 it would encourage
> me to look at the other 300 cases ?

Patches must be bootstrapped+regression tested and sent to gcc-patches. Check 
http://gcc.gnu.org/contribute.html for further instructions. If you need help
with a particular step, write me an email. Examples of submissions can be found
in the archives of gcc-patches.


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manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
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                 CC|                            |manu at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34592

[Bug other/34592] useless computation found

[manu at gcc dot gnu dot org]

------- Comment #7 from manu at gcc dot gnu dot org  2010-05-06 10:59 -------
Thanks for the report. I think all these have been fixed already in GCC 4.6 and
regressions would be detected by the new -Wunused-but-set flags.


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manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34592