On June 15, 2020 6:31:38 PM GMT+02:00, Shuai Wang via Gcc <gcc@gcc.gnu.org>
wrote:
>Hello,
>
>Suppose given the following SSA statement generated by the `sanopt`
>pass:
>
> _17 = (signed char *) _16;
> _18 = *_17;
>
>I am using the following code to identify that _17 depends on _16:
>
>// def_stmt refers to _18 = &_17;
>for (unsigned i = 1; i < gimple_num_ops(def_stmt); i++) {
> op1 = gimple_assign_rhs1(def_stmt);
> if (is_gimple_addressable(op1)) {
> gimple* def_stmt = SSA_NAME_DEF_STMT(op1);
> print_gimple_stmt(stderr, def_stmt, 0, TDF_SLIM); // crash at
>this point
> }
>
>It crashes with the following call stack:
>
>0xb5cd5f crash_signal
> ../../gcc-10.1.0/gcc/toplev.c:328
>0x1452134 pp_format(pretty_printer*, text_info*)
> ../../gcc-10.1.0/gcc/pretty-print.c:1828
>0x14533e4 pp_printf(pretty_printer*, char const*, ...)
> ../../gcc-10.1.0/gcc/pretty-print.c:1773
>0x8dcc81 print_gimple_stmt(_IO_FILE*, gimple*, int, dump_flag)
> ../../gcc-10.1.0/gcc/gimple-pretty-print.c:157
>
>I tried hard but just cannot understand why this would crash. Indeed,
>this
>code works pretty well when printing out other dependency statements,
>but
>just gets stuck in front of pointer dereference like _18 = *_17.
>
>Any suggestion would be appreciated. Thank you!
Build your compiler with - - enable-checking and you'll figure you reference
SSA_NAME_DEF_STMT of a NON-SSA_NAME. I suggest you learn to use a debugger.
Richard.
>Best,
>Shuai
