Re: [PATCH]: Fix missed PRE optimization discovered

["Richard Guenther" <richard dot guenther at gmail dot com>]

On Sat, Oct 18, 2008 at 4:02 AM, Daniel Berlin <dberlin@dberlin.org> wrote:
> I'm currently testing the following, which at least doesn't crash on
> the minimized testcase i produced :)

Looking at that patch I wonder if

-          if (TREE_TYPE (constant) != type)
+         if (!useless_type_conversion_p (type, TREE_TYPE (constant)))

will also work.

Richard.

>
> Index: tree-ssa-pre.c
> ===================================================================
> --- tree-ssa-pre.c      (revision 141195)
> +++ tree-ssa-pre.c      (working copy)
> @@ -3022,21 +3022,13 @@
>          if (TREE_TYPE (constant) != type)
>            {
>              tree builtexpr = fold_convert (type, constant);
> -             if (is_gimple_min_invariant (builtexpr))
> +             if (!is_gimple_min_invariant (builtexpr))
>                {
> -                 PRE_EXPR_CONSTANT (eprime) = builtexpr;
> -               }
> -             else
> -               {
>                  tree forcedexpr = force_gimple_operand (builtexpr,
>                                                          &stmts, true,
>                                                          NULL);
> -                 if (is_gimple_min_invariant (forcedexpr))
> +                 if (!is_gimple_min_invariant (forcedexpr))
>                    {
> -                     PRE_EXPR_CONSTANT (eprime) = forcedexpr;
> -                   }
> -                 else
> -                   {
>                      if (forcedexpr != builtexpr)
>                        {
>                          VN_INFO_GET (forcedexpr)->valnum = PRE_EXPR_CONSTANT (eprime);
>
>
> On Fri, Oct 17, 2008 at 2:34 PM, Laurent GUERBY <laurent@guerby.net> wrote:
>> On Fri, 2008-10-17 at 19:17 +0200, Eric Botcazou wrote:
>>> > Doesn't break on x86_64-linux-gnu for me (ubuntu hardy), trying
>>> > i686-pc-linux-gnu.
>>>
>>> Really sure?  Our x86 and x86-64 testers are down and Laurent Guerby's tester
>>> on x86-64 hasn't posted anything to gcc-results@ since rev 141181.
>>
>> I confirm 141181 was the last to bootstrap c,ada on x86_64,
>> the next update of the build script led to a failure:
>>
>> Fri Oct 17 04:18:33 CEST 2008
>> Updating SVN tree
>> U    gcc/DATESTAMP
>> U    gcc/ChangeLog
>> U    gcc/tree-ssa-pre.c
>> Updated to revision 141186.
>> ...
>>
>> raised STORAGE_ERROR : stack overflow (or erroneous memory access)
>> gnatmake: "/home/guerby/trunk/gcc/ada/gnatname.adb" compilation error
>> make[3]: *** [common-tools] Error 4
>> make[3]: Leaving directory `/home/guerby/build/gcc/ada/tools'
>> make[2]: *** [gnattools-native] Error 2
>> make[2]: Leaving directory `/home/guerby/build/gnattools'
>> make[1]: *** [all-gnattools] Error 2
>> make[1]: Leaving directory `/home/guerby/build'
>> make: *** [bootstrap] Error 2
>> Fri Oct 17 06:22:24 CEST 2008
>>
>> For reference, the configure line of my build script is:
>>
>> ../trunk/configure --prefix=/n/11/guerby/install-trunk
>> --enable-languages=c,ada --enable-__cxa_atexit --disable-nls
>> --enable-threads=posix --with-mpfr=/opt/cfarm/mpfr-2.3.1
>>
>> And base version of GCC is "4.1.2 20061115 (prerelease) (Debian
>> 4.1.1-21)".
>>
>> Laurent
>>
>>
>>
>