Error:
>$ g++ -c -O3 func.cpp
func.cpp: In function ‘void test()’:
func.cpp:5:6: error: definition in block 3 follows the use
    5 | void test() {
      |      ^~~~
for SSA_NAME: var_5.3_5 in statement:
vect__6.8_50 = vect__4.7_58 << var_5.3_5;
during GIMPLE pass: slp
func.cpp:5:6: internal compiler error: verify_ssa failed
0x1339a82 verify_ssa(bool, bool)
	gcc/tree-ssa.c:1208
0x1025705 execute_function_todo
	gcc/passes.c:1992
0x10263de execute_todo
	gcc/passes.c:2039

Reproducer:
extern short var_3, var_8;
extern int var_5;
extern char var_10;
extern int arr_99[][16];
void test() {
  for (; 0 < var_10;)
    for (long a(var_8);; a++)
      arr_99[4][a] = var_3 << var_5;
}

GCC version:
11.0.0 20200625 (77d455ee81ec3a23f8b20259a31ab963716f8e82)