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Re: [gimplefe] "Unknown tree: c_maybe_const_expr" error while parsing conditional expression


On 2 August 2016 at 14:29, Richard Biener <richard.guenther@gmail.com> wrote:
> On Mon, Aug 1, 2016 at 4:52 PM, Prasad Ghangal <prasad.ghangal@gmail.com> wrote:
>> Hi,
>>
>> I am trying to replace c_parser_paren_condition (parser) in
>> c_parser_gimple_if_stmt by c_parser_gimple_paren_condition (parser) as
>> described in the patch
>>
>> I am trying test case
>> void __GIMPLE () foo ()
>> {
>>   int a;
>> bb_2:
>>   if (a == 2)
>>     goto bb_3;
>>   else
>>     goto bb_4;
>> bb_3:
>>   a_2 = 4;
>> bb_4:
>>   return;
>> }
>>
>> but it fails to parse gimple expression and produces error as
>> /home/prasad/test3.c: In function ‘foo’:
>> /home/prasad/test3.c:1:18: error: invalid operands in gimple comparison
>>  void __GIMPLE () foo ()
>>                   ^~~
>> if (<<< Unknown tree: c_maybe_const_expr
>>
>>   a >>> == 2) goto bb_3; else goto bb_4;
>> /home/prasad/test3.c:1:18: internal compiler error: verify_gimple failed
>>
>> I failed to debug where it is setting to C_MAYBE_CONST_EXPR
>
> It's in parsing the binary expression.  Btw, you don't need lvalue_to_rvalue
> conversion or truthvalue conversion - source that would require this would
> not be valid GIMPLE.  Let me try to debug:
>
>
> (gdb) p debug_tree (cond.value)
>  <eq_expr 0x7ffff6997960
>     type <integer_type 0x7ffff688b7e0 int public SI
>         size <integer_cst 0x7ffff6887ee8 constant 32>
>         unit size <integer_cst 0x7ffff6887f00 constant 4>
>         align 32 symtab 0 alias set -1 canonical type 0x7ffff688b7e0
> precision 32 min <integer_cst 0x7ffff6887ea0 -2147483648> max
> <integer_cst 0x7ffff6887eb8 2147483647>
>         pointer_to_this <pointer_type 0x7ffff68a5930>>
>
>     arg 0 <c_maybe_const_expr 0x7ffff6997938 type <integer_type
> 0x7ffff688b7e0 int>
>
>         arg 1 <var_decl 0x7ffff7fefcf0 a type <integer_type 0x7ffff688b7e0 int>
>             used SI file t.c line 3 col 7 size <integer_cst
> 0x7ffff6887ee8 32> unit size <integer_cst 0x7ffff6887f00 4>
>             align 32 context <function_decl 0x7ffff699c500 foo>>>
>     arg 1 <integer_cst 0x7ffff68a4318 type <integer_type
> 0x7ffff688b7e0 int> constant 2>
>     t.c:5:9 start: t.c:5:7 finish: t.c:5:12>
> $5 = void
> (gdb) b ggc-page.c:1444 if result == 0x7ffff6997938
> Breakpoint 6 at 0x8a0d3e: file
> /space/rguenther/src/gcc_gimple_fe/gcc/ggc-page.c, line 1444.
> (gdb) run
>
> Breakpoint 6, ggc_internal_alloc (size=40, f=0x0, s=0, n=1)
>     at /space/rguenther/src/gcc_gimple_fe/gcc/ggc-page.c:1444
> 1444      return result;
> (gdb) fin (a few times)
> Run till exit from #0  0x00000000011821b7 in build2_stat (
>     code=C_MAYBE_CONST_EXPR, tt=<integer_type 0x7ffff688b7e0 int>,
>     arg0=<tree 0x0>, arg1=<var_decl 0x7ffff7fefcf0 a>)
>     at /space/rguenther/src/gcc_gimple_fe/gcc/tree.c:4466
> 0x000000000081d263 in c_wrap_maybe_const (expr=<var_decl 0x7ffff7fefcf0 a>,
>     non_const=false)
>     at /space/rguenther/src/gcc_gimple_fe/gcc/c-family/c-common.c:4359
> 4359      expr = build2 (C_MAYBE_CONST_EXPR, TREE_TYPE (expr), NULL, expr);
> Value returned is $11 = (tree_node *) 0x7ffff6997938
> (gdb) up
> #1  0x00000000007b8e81 in build_binary_op (location=176833, code=EQ_EXPR,
>     orig_op0=<var_decl 0x7ffff7fefcf0 a>,
>     orig_op1=<integer_cst 0x7ffff68a4318>, convert_p=1)
>     at /space/rguenther/src/gcc_gimple_fe/gcc/c/c-typeck.c:11549
> 11549                       op0 = c_wrap_maybe_const (op0, !op0_maybe_const);
>
> and this is guarded by !in_late_binary_op (which also seems to guard folding).
> So I suggest to somewhere at the start of parsing to set in_late_binary_op to
> true for -fgimple.  Not sure if it works for everything, but you
> should have accumulated
> quite some tests for -fgimple in the testsuite to make sure it doesn't
> regress anything.
>
I did bootstrap build for the trunk and testing is in progress. How
can I test with -fgimple flag enabled?


Thanks,
Prasad
> The following works for me:
>
> diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
> index 70800a2..c8c087a 100644
> --- a/gcc/c/c-parser.c
> +++ b/gcc/c/c-parser.c
> @@ -2158,7 +2159,10 @@ c_parser_declaration_or_fndef (c_parser
> *parser, bool fndef_ok,
>
>        if (gimple_body_p && flag_gimple)
>         {
> +         bool saved = in_late_binary_op;
> +         in_late_binary_op = true;
>           c_parser_parse_gimple_body (parser);
> +         in_late_binary_op = saved;
>           cgraph_node::finalize_function (current_function_decl, false);
>           timevar_pop (tv);
>           return;
>
>
> Richard.
>
>>
>> Thanks,
>> Prasad


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