[Bug tree-optimization/126936] New: ICE at -O3 on x86_64-linux-gnu during SLP pass: verify_ssa failed due to definition following use

[xintong.zhou1 at uwaterloo dot ca via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126936

            Bug ID: 126936
           Summary: ICE at -O3 on x86_64-linux-gnu during SLP pass:
                    verify_ssa failed due to definition following use
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: xintong.zhou1 at uwaterloo dot ca
  Target Milestone: ---

Compiler Explorer: https://godbolt.org/z/5P555oeqT

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=/data/x27zhou/compiler-nightly/install/gcc/bin/gcc
COLLECT_LTO_WRAPPER=/data/x27zhou/compiler-nightly/install/gcc/libexec/gcc/x86_64-pc-linux-gnu/17.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /data/x27zhou/compiler-nightly/src/gcc/configure CC='ccache
clang' CXX='ccache clang++' --enable-checking=yes
--disable-bootstrap--disable-multilib --enable-languages=c,c++
--prefix=/data/x27zhou/compiler-nightly/install/gcc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 17.0.0 20260818 (experimental) (GCC)
$
$ gcc-trunk -O3 small.c
small.c: In function ‘fn1’:
small.c:3:6: error: definition in block 4 follows the use
    3 | void fn1() {
      |      ^~~
for SSA_NAME: _157 in statement:
_163 = BIT_FIELD_REF <_157, 32, 0>;
during GIMPLE pass: slp
small.c:3:6: internal compiler error: verify_ssa failed
0x25e658f internal_error(char const*, ...)
       
/data/x27zhou/compiler-nightly/src/gcc/gcc/diagnostic-global-context.cc:787
0x1337f20 verify_ssa(bool, bool)
        /data/x27zhou/compiler-nightly/src/gcc/gcc/tree-ssa.cc:1226
0xf0f404 execute_function_todo(function*, void*)
        /data/x27zhou/compiler-nightly/src/gcc/gcc/passes.cc:2107
0xf0dcf1 execute_todo(unsigned int)
        /data/x27zhou/compiler-nightly/src/gcc/gcc/passes.cc:2152
/data/x27zhou/compiler-nightly/install/gcc/libexec/gcc/x86_64-pc-linux-gnu/17.0.0/cc1
-quiet -imultiarch x86_64-linux-gnu small.c -quiet -dumpdir a- -dumpbase
small.c -dumpbase-ext .c -mtune=generic -march=x86-64 -O3 -o /tmp/ccQdY2jM.s
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
$
$ cat small.c
int *c;
char d;
void fn1() {
  for (; *(c + 78 % 16);)
    ;
  for (int e = 0; e < 32; e += 2) {
    d = c[e & 15] % 3u;
    c[0] = c[0] & d;
  }
}
int main() {}