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Re: [PATCH] Remove bogus optimization from may_alias_p
On Tue, Oct 21, 2008 at 5:07 PM, Richard Guenther
<richard.guenther@gmail.com> wrote:
> On Tue, Oct 21, 2008 at 4:47 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>>> Bootstrapped and tested on x86_64-unknown-linux-gnu for the trunk
>>> and the gcc-4_3-branch. Committed to trunk and the branch.
>>>
>>> Richard.
>>>
>>> 2008-10-19 Richard Guenther <rguenther@suse.de>
>>>
>>> * tree-ssa-alias.c (may_alias_p): Remove bogus shortcut.
>>
>> On the 4.3 branch this causes lots of warnings during bootstrap of the form:
>>
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c: In
>> function 'pp_base_format':
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:433: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:433 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:435: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:435 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:435: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long long int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:435 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:441: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:441 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:444: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:444 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:444: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:444 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:453: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'void *' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:453 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:458: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:458 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:461: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:461 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:461: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:461 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:467: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:467 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:470: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:470 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:470: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long long unsigned int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:470 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:476: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'location_t *' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:476 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>>
>>
>> More annoyingly, this doesn't always reproduce manually:
>>
>> eric@atlantis:~/build/gcc-4_3-branch/native32/gcc> rm pretty-print.o
>> eric@atlantis:~/build/gcc-4_3-branch/native32/gcc> /home/eric/build/gcc-4_3-branch/native32/./prev-gcc/xgcc -B/home/eric/build/gcc-4_3-branch/native32/./prev-gcc/ -B/home/eric/install/gcc-4_3-branch/i586-suse-linux/bin/ -c -g -O2 -fomit-frame-pointer -DIN_GCC -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmissing-format-attribute -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -DHAVE_CONFIG_H -I. -I. -I/home/eric/svn/gcc-4_3-branch/gcc -I/home/eric/svn/gcc-4_3-branch/gcc/. -I/home/eric/svn/gcc-4_3-branch/gcc/../include -I/home/eric/svn/gcc-4_3-branch/gcc/../libcpp/include -I/home/eric/svn/gcc-4_3-branch/gcc/../libdecnumber -I/home/eric/svn/gcc-4_3-branch/gcc/../libdecnumber/bid -I../libdecnumber /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c -o
>> pretty-print.o
>> eric@atlantis:~/build/gcc-4_3-branch/native32/gcc> rm pretty-print.o ; make
>> quickstrap
>> /home/eric/build/gcc-4_3-branch/native32/./prev-gcc/xgcc -B/home/eric/build/gcc-4_3-branch/native32/./prev-gcc/ -B/home/eric/install/gcc-4_3-branch/i586-suse-linux/bin/ -c -g -O2 -fomit-frame-pointer -DIN_GCC -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmissing-format-attribute -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -DHAVE_CONFIG_H -I. -I. -I/home/eric/svn/gcc-4_3-branch/gcc -I/home/eric/svn/gcc-4_3-branch/gcc/. -I/home/eric/svn/gcc-4_3-branch/gcc/../include -I/home/eric/svn/gcc-4_3-branch/gcc/../libcpp/include -I/home/eric/svn/gcc-4_3-branch/gcc/../libdecnumber -I/home/eric/svn/gcc-4_3-branch/gcc/../libdecnumber/bid -I../libdecnumber /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c -o
>> pretty-print.o
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c: In
>> function 'pp_base_format':
>> /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:433: warning: likely
>> type-punning may break strict-aliasing rules: object '*{unknown}' of main
>> type 'long int' is referenced at or
>> around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:433 and may be
>> aliased to object '_sch_istable' of main type 'short unsigned int' which is
>> referenced at or around /home/eric/svn/gcc-4_3-branch/gcc/pretty-print.c:284.
>> [...]
>>
>>
>> Any idea as to where this can come from?
>
> Hm, I on purpose did testing on the 4.3 branch with checking enabled
> to catch such
> stuff -- but appearantly enablin checking doesn't enable Werror there ...
It doesn't reproduce for me. How did you configure gcc, and on which target?
Thanks,
Richard.