[Bug c/126876] New: [17 regression] ice in ssa_range_in_phi

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126876

            Bug ID: 126876
           Summary: [17 regression] ice in ssa_range_in_phi
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

Created attachment 65335
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65335&action=edit
C source code

The attached code does this with recent gcc trunk:

$ ../results/bin/gcc -c -O2 -w bug1235.c
during GIMPLE pass: thread
/home/dcb42/rpmbuild/BUILD/ktextaddons-2.1.0-build/ktextaddons-2.1.0/textutils/cmark-rc/blocks.c:
In function ‘S_parser_feed’:
/home/dcb42/rpmbuild/BUILD/ktextaddons-2.1.0-build/ktextaddons-2.1.0/textutils/cmark-rc/blocks.c:635:13:
internal compiler error: Segmentation fault
  635 | static void S_parser_feed(cmark_parser *parser, const unsigned char
*buffer, size_t len, bool eof)
      |             ^~~~~~~~~~~~~
0x21ad017 internal_error
       
/home/dcb42/gcc/working/gcc/../../trunk/gcc/diagnostic-global-context.cc:787
0xc91c49 ???
        /home/dcb42/gcc/working/gcc/../../trunk/gcc/toplev.cc:325
0xea62b7 ssa_range_in_phi
        /home/dcb42/gcc/working/gcc/../../trunk/gcc/gimple-range-path.cc:262
0xea5d8c range_defined_in_block
        /home/dcb42/gcc/working/gcc/../../trunk/gcc/gimple-range-path.cc:303
0xea5bbb internal_range_of_expr
        /home/dcb42/gcc/working/gcc/../../trunk/gcc/gimple-range-path.cc:160

The bug first seems to occur sometime between g:424bd64ef45e001c
and g:736361789c1309e3

Compiler is

$ ../results/bin/gcc -v
Using built-in specs.
COLLECT_GCC=../results/bin/gcc
COLLECT_LTO_WRAPPER=/home/dcb42/gcc/results.20260814.ubsan/libexec/gcc/x86_64-pc-linux-gnu/17.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../trunk/configure
--prefix=/home/dcb42/gcc/results.20260814.ubsan --disable-bootstrap
--disable-doc --disable-multilib --with-build-config=bootstrap-ubsan
--with-pkgversion=736361789c1309e3 --enable-checking=yes
--enable-languages=c,c++,fortran
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 17.0.0 20260814 (experimental) (736361789c1309e3) 
$