[Bug middle-end/126772] New: ICE:: in trunc_int_for_mode, at explow.cc:59 for fixed-point negative shift

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126772

            Bug ID: 126772
           Summary: ICE:: in trunc_int_for_mode, at explow.cc:59 for
                    fixed-point negative shift
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gjl at gcc dot gnu.org
  Target Milestone: ---

_Accum shift (_Accum a)
{
    return a << -1;
}

$ avr-gcc -S y.c
y.c: In function 'shift':
y.c:3:14: warning: left shift count is negative [-Wshift-count-negative]
    3 |     return a << -1;
      |              ^~
during RTL pass: expand
y.c:3:14: internal compiler error: in trunc_int_for_mode, at explow.cc:59
    3 |     return a << -1;
      |            ~~^~~~~

Target: avr
Configured with: ../../source/gcc-master/configure --target=avr --disable-nls
--with-dwarf2 --with-gnu-as --with-gnu-ld --with-long-double=64
--enable-languages=c,c++
Thread model: single
Supported LTO compression algorithms: zlib
gcc version 17.0.0 20260722 (experimental) (GCC)