On Tue, Jun 16, 2020 at 5:00 AM Shuai Wang <wangshuai...@gmail.com> wrote:
>
> Yes, TREE_CODE (op1) != SSA_NAME shows that op1 is by no means SSA names
> (although I don't know why). But how can I backwardly identify its
> initialization statement _17 = (signed char *) _16? Thanks!
You want to walk over SSA operands of the stmt, not over operands
using for example FOR_EACH_SSA_USE_OPERAND.
> Shuai
>
> On Tue, Jun 16, 2020 at 10:32 AM Shuai Wang <wangshuai...@gmail.com> wrote:
>>
>> Got it. But in that sense, given a `op1` satisfies the
>> "is_gimple_addressable" predicate (e.g., the _17 in my sample code), how can
>> I find its def statement? Thank you very much.
>>
>> Shuai
>>
>> On Tue, Jun 16, 2020 at 3:19 AM Richard Biener <richard.guent...@gmail.com>
>> wrote:
>>>
>>> On June 15, 2020 6:58:27 PM GMT+02:00, Shuai Wang <wangshuai...@gmail.com>
>>> wrote:
>>> >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);
>>>
>>> op1 is not an SSA name here.
>>>
>>> >> > if (is_gimple_addressable(op1))
>>>
>>> That predicate does not make sense on SSA names
>>>
>>> {
>>> >> > 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
>>> >>
>>> >>
>>>
