[Bug tree-optimization/114038] New: wrong code with __builtin_mul_overflow_p() and _BitInt() at -O0

[Bug tree-optimization/114038] New: wrong code with __builtin_mul_overflow_p() and _BitInt() at -O0

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114038

            Bug ID: 114038
           Summary: wrong code with __builtin_mul_overflow_p() and
                    _BitInt() at -O0
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
                CC: jakub at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

Created attachment 57481
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57481&action=edit
reduced testcase

Output:
$ x86_64-pc-linux-gnu-gcc testcase.c 
$ ./a.out 
Aborted

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r14-9091-20240220194451-g0a6a5f8656c-checking-yes-rtl-df-extra-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/14.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--with-cloog --with-ppl --with-isl --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu
--with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r14-9091-20240220194451-g0a6a5f8656c-checking-yes-rtl-df-extra-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.1 20240221 (experimental) (GCC)

[Bug tree-optimization/114038] wrong code with __builtin_mul_overflow_p() and _BitInt() at -O0

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114038

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2024-02-21
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 57484
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57484&action=edit
gcc14-pr114038.patch

Untested fix.

[Bug tree-optimization/114038] wrong code with __builtin_mul_overflow_p() and _BitInt() at -O0

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114038

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:853cbcb7a74ecd95efcba25279b270f0a868d584

commit r14-9131-g853cbcb7a74ecd95efcba25279b270f0a868d584
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Feb 22 10:14:00 2024 +0100

    bitintlower: Fix .MUL_OVERFLOW overflow checking [PR114038]

    Currently, bitint_large_huge::lower_mul_overflow uses cnt 1 only if
    startlimb == endlimb and in that case doesn't use a loop and handles
    everything in a special if:
          unsigned cnt;
          bool use_loop = false;
          if (startlimb == endlimb)
            cnt = 1;
          else if (startlimb + 1 == endlimb)
            cnt = 2;
          else if ((end % limb_prec) == 0)
            {
              cnt = 2;
              use_loop = true;
            }
          else
            {
              cnt = 3;
              use_loop = startlimb + 2 < endlimb;
            }
          if (cnt == 1)
            {
              ...
            }
          else
    The loop handling for the loop exit condition wants to compare if the
    incremented index is equal to endlimb, but that is correct only if
    end is not divisible by limb_prec and there will be a straight line
    check after the loop as well for the most significant limb.  The code
    used endlimb + (cnt == 1) for that, but cnt == 1 is never true here,
    because cnt is either 2 or 3, so the right check is (cnt == 2).

    2024-02-22  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/114038
            * gimple-lower-bitint.cc (bitint_large_huge::lower_mul_overflow):
Fix
            loop exit condition if end is divisible by limb_prec.

            * gcc.dg/torture/bitint-59.c: New test.

[Bug tree-optimization/114038] wrong code with __builtin_mul_overflow_p() and _BitInt() at -O0

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114038

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.