[Bug tree-optimization/123372] [15 Regression] ICE in expand_fn_using_insn on .SAT_SUB while building OpenTTD with LTO since r15-1671

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123372

--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-15 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:5d343a467ba03606ff3f4c27b7b49b2b79015593

commit r15-10690-g5d343a467ba03606ff3f4c27b7b49b2b79015593
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Jan 3 14:27:41 2026 +0100

    widening_mul: Fix up .SAT_{ADD,SUB,MUL} pattern recognition [PR123372]

    The following testcase ICEs since r15-1671, because the match.pd pattern
    now allows a cast and the function checks whether the ifn is supported
    on a wrong type.  .SAT_{ADD,SUB,MUL} are binary ifns, so they care about
    the type of their first operand:
      #define binary_direct { 0, 0, true }
    where
      /* optabs can be parameterized by one or two modes.  These fields
describe
         how to select those modes from the types of the return value and
         arguments.  A value of -1 says that the mode is determined by the
         return type while a value N >= 0 says that the mode is determined by
         the type of argument N.  A value of -2 says that this internal
         function isn't directly mapped to an optab.  */
    but in this function (unlike the function right below it for the
    same ifns) checks the type of the lhs which since that change can be
    actually a different type (expansion performs the operation on the
    argument types and then casts the result to the lhs type).
    So, e.g. on x86_64 -m32, it checks wether ussubsi3 insn can be used
    (which it can), but then actually uses it on DImode arguments and
    ussubdi3 is TARGET_64BIT only.  Similarly for -m64 it checks ussubsi3 too
    instead of ussubti3 (which doesn't exist).

    2026-01-03  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/123372
            * tree-ssa-math-opts.cc
            (build_saturation_binary_arith_call_and_replace): Pass type of op_0
            rather than type of lhs as second argument to
            direct_internal_fn_supported_p.

            * gcc.dg/tree-ssa/pr123372.c: New test.

    (cherry picked from commit c7206efa282bdd121ae4bd5227b487d06c3874c2)