[Bug tree-optimization/79345] [6/7 Regression] passing yet-uninitialized member as argument to base class constructor should warn (-Wunitialized)

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79345

--- Comment #14 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 1 Mar 2017, jakub at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79345
> 
> --- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> (In reply to Richard Biener from comment #9)
> > actually the genemit fix doensn't fully work:
> > 
> > /space/rguenther/src/svn/trunk/gcc/config/i386/i386.md: In function
> > ‘rtx_def* gen_smulsi3_highpart(rtx, rtx, rtx)’:
> > /space/rguenther/src/svn/trunk/gcc/config/i386/i386.md:7380:26: error:
> > ‘operands[3]’ is used uninitialized in this function [-Werror=uninitialized]
> >         (any_extend:TI
> >                 ~~~~~~    ^
> > /space/rguenther/src/svn/trunk/gcc/config/i386/i386.md: In function
> > ‘rtx_def* gen_umulsi3_highpart(rtx, rtx, rtx)’:
> > /space/rguenther/src/svn/trunk/gcc/config/i386/i386.md:7380:26: error:
> > ‘operands[3]’ is used uninitialized in this function [-Werror=uninitialized]
> >         (any_extend:TI
> >                 ~~~~~~    ^
> > ...
> > 
> > bah.
> 
> --- gcc/genemit.c.jj    2017-01-01 12:45:35.000000000 +0100
> +++ gcc/genemit.c       2017-03-01 10:51:27.474179940 +0100
> @@ -518,6 +518,9 @@ gen_expand (md_rtx_info *info)
>         {
>           for (i = 0; i < stats.num_operand_vars; i++)
>             {
> +             if (i > MAX (stats.max_opno, stats.max_dup_opno)
> +                 && i <= stats.max_scratch_opno)
> +               continue;
>               printf ("    operand%d = operands[%d];\n", i, i);
>               printf ("    (void) operand%d;\n", i);
>             }
> 
> should fix that.  Even if some define_insn doesn't have any match_dups, it can
> still have normal operands.

Looks like we have patterns with dups after scratches:

(define_expand "<s>mul<mode>3_highpart"
  [(parallel [(set (match_operand:SWI48 0 "register_operand")
                   (truncate:SWI48
                     (lshiftrt:<DWI>
                       (mult:<DWI>
                         (any_extend:<DWI>
                           (match_operand:SWI48 1 "nonimmediate_operand"))
                         (any_extend:<DWI>
                           (match_operand:SWI48 2 "register_operand")))
                       (match_dup 4))))
              (clobber (match_scratch:SWI48 3))
              (clobber (reg:CC FLAGS_REG))])]

which then still warns:

/space/rguenther/src/svn/trunk/gcc/config/i386/i386.md: In function 
‘rtx_def* gen_umulsi3_highpart(rtx, rtx, rtx)’:
/space/rguenther/src/svn/trunk/gcc/config/i386/i386.md:7380:14: warning: 
‘operands[3]’ is used uninitialized in this function [-Wuninitialized]
        (any_extend:TI
        ~~~~~~^~~~~~~~     
...