Thank you very much for your prompt response, Rchard. Sorry I was kinda
"learning by doing". I am familiar with LLVM stuff but newbie to GCC
specifications.
Just want to make sure I got it right; _17 and _16 in the IR code are SSA
variables. They are initialized for once and used once. Could you please
shed some light on where "non-ssa name" comes in this scenario, and how
exactly can I get _17 = (signed char *) _16 printed out? Thank you very
much.
Best,
Shuai
On Tue, Jun 16, 2020 at 12:52 AM Richard Biener <richard.guent...@gmail.com>
wrote:
> 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
>
>
