Crash at gimple_code(gimple* )

[Shuai Wang via Gcc]

Hello,

I am using the following code to iterate different gimple statements:

...
 gimple* stmt = gsi_stmt(gsi);
if (gimple_assign_load_p(stmt)) {
     tree rhs = gimple_assign_rhs1 (stmt);
     if (!rhs) return;
      gimple* def_stmt = SSA_NAME_DEF_STMT(rhs);
      if (!def_stmt) return;

     switch (gimple_code (def_stmt)) {
         ....
     }
}

While the above code works smoothly for most of the cases, to my surprise,
the following statement (pointed by gsi) would cause a crash at
gimple_code(def_stmt):

stderr.9_1 = stderr;

It seems that `stderr` is a special tree node; however, it successfully
passes the two if checks and reaches the gimple_code(def_stmt), but still
caused an exception:

0xb5cd5f crash_signal
        ../../gcc-10.1.0/gcc/toplev.c:328
0x7f4214557838 gimple_code

/export/d1/shuaiw/gcc-build-10/gcc-install/lib/gcc/x86_64-pc-linux-gnu/10.1.0/plugin/include/gimple.h:1783
....

Am I missing anything?

Best,
Shuai