Re: [gcc front end] problem with -O* flags

[Philip Herron <redbrain at gcc dot gnu dot org>]

On 15 June 2011 18:14, charfi asma <charfiasma@yahoo.fr> wrote:
> Hello,
>
> I built a new gcc front end that produce this GIMPLE:
>
> main ()
> gimple_bind <
> ?<unnamed-signed:32> D.35;
> ?struct MyClass x;
>
> ?gimple_call <MyOperation1, NULL, &x>
> ?gimple_assign <integer_cst, D.35, 0, NULL>
> ?gimple_return <D.35>
>>
>
>
> MyOperation1 (struct MyClass * this)
> gimple_bind <
> ?gimple_assign <integer_cst, My_Var, 100, NULL>
> ?gimple_assign <integer_cst, this->MyAttribute1, 50, NULL>
> ?gimple_return <NULL>
>>
>
>
> which is equivalent to the C++ code:
>
> class MyClass
> {
> public: void MyOperation1()
> {
> ? ?int My_Var=10;
> ? ?My_Var=100;
> ? ?myAttribute=50;
>
> }
> int myAttribute;
>
> };
>
> int main()
> {
> ? ?MyClass x ;
> ? ?x.MyOperation1();
> ? ?return 0;
> }
>
>
> when I run my compiler (called guml) ?: ?guml test.uml ?-fdump-tree-gimple-raw
> , ?it generates the gimple above.
> however when I run it using -O1, O2, O3 or Os guml test.uml
> -fdump-tree-gimple-raw -Os, ? it generates a seg fault.
>
> I used gdb to debug, and I discover that the error comes from the modifications
> of MyAttribute1 ? gimple_assign <integer_cst, this->MyAttribute1, 50, NULL>
> because if I remove the equivalent GENERIC tree, the compilation works fine even
> with -Os.
>
> the error comes more precisely when tring to run the ipa optimisations
>
> Analyzing compilation unit
> Performing interprocedural optimizations
> ?<*free_lang_data> <visibility> <early_local_cleanups>
> Breakpoint 1, execute_ipa_pass_list (pass=0x1168800) at
> ../../gcc/gcc/passes.c:1928
> 1928 ? ? ? ? ? ? ? ? ?do_per_function_toporder ((void (*)(void
> *))execute_pass_list,
> ......
> 1131 ? ? ? ? ?for (i = nnodes - 1; i >= 0; i--)
> (gdb) n
> 1133 ? ? ? ? ? ? ?struct cgraph_node *node = order[i];
> (gdb) n
> 1136 ? ? ? ? ? ? ?order[i] = NULL;
> (gdb) n
> 1137 ? ? ? ? ? ? ?node->process = 0;
> (gdb) n
> 1138 ? ? ? ? ? ? ?if (node->analyzed)
> (gdb) n
> 1140 ? ? ? ? ? ? ? ? ?push_cfun (DECL_STRUCT_FUNCTION (node->decl));
> (gdb) n
> 1141 ? ? ? ? ? ? ? ? ?current_function_decl = node->decl;
> (gdb) n
> 1142 ? ? ? ? ? ? ? ? ?callback (data);
> (gdb) n
> 1141 ? ? ? ? ? ? ? ? ?current_function_decl = node->decl;
> (gdb) n
> 1142 ? ? ? ? ? ? ? ? ?callback (data);
> (gdb) n
>
> Program received signal SIGSEGV, Segmentation fault.
> fold_convertible_p (type=0x0, arg=0x7f2bf778a1e0) at
> ../../gcc/gcc/fold-const.c:1830
> 1830 ? ? ? ? ?|| TREE_CODE (orig) == ERROR_MARK)
>
>
> In a normal compilation, the debugger should print:
> Performing interprocedural optimizations
> ?<*free_lang_data> <visibility> <early_local_cleanups> <whole-program>
> <inline>Assembling functions:
> ?MyOperation1 main
>
>
> so I think that the error comes from Whole-program optimization.
>
> This is how I set MyOperation1() body
>
> tree __func_param = NULL_TREE;
> tree parm_type = build_pointer_type(class_t);
> tree parm = build_decl (BUILTINS_LOCATION, PARM_DECL, get_identifier("this"),
> parm_type);
> TREE_CONSTANT (parm) = true;
> TREE_READONLY (parm) = true;
>
>
> DECL_CHAIN (parm) = __func_param;
> __func_param = parm;
> DECL_ARGUMENTS(operation)=(__func_param);
>
>
> // return type preparation
>
> tree __func_result = build_decl(BUILTINS_LOCATION, RESULT_DECL, NULL_TREE,
> TREE_TYPE(operation));
> DECL_CONTEXT(__func_result) = operation;
> DECL_ARTIFICIAL(__func_result) = true;
> DECL_IGNORED_P(__func_result) = true;
> DECL_RESULT(operation) = __func_result;
>
>
> // debug tree needed for bind exp
>
> tree __func_art_block = build_block(NULL_TREE, NULL_TREE, NULL_TREE, NULL_TREE);
> DECL_INITIAL(operation) = __func_art_block;
>
>
> //stmt tree for the body
>
> tree func_stmts = alloc_stmt_list ();
>
> //set the body
>
> ? ?tree var = build_decl(BUILTINS_LOCATION, VAR_DECL, get_identifier("My_Var"),
> integer_type_node);
> ? ?TREE_STATIC(var) = true;
> ? ?TREE_PUBLIC(var) = true;
> ? ?DECL_CONTEXT(var) = operation;
> ? ?TREE_USED(var) = true;
> ? ?DECL_INITIAL (var) = build_int_cst(integer_type_node, 10 );
>
> ? ?layout_decl(var, false);
> ? ?rest_of_decl_compilation(var, 1, 0);
>
> ? ?append_to_statement_list(var, &func_stmts);
>
>
> ? ?tree val = build_int_cst(integer_type_node, 100);
> ? ?tree modify_att_tree = build2(MODIFY_EXPR, TREE_TYPE(var), var, val);
>
> ? ?append_to_statement_list(modify_att_tree, &func_stmts);
>
>
> ? ?tree t = TREE_TYPE(TREE_TYPE(parm));
>
> ? ?tree ref = build1 (INDIRECT_REF, t, parm);
>
> ? ?tree __struct_field0 = TYPE_FIELDS(TREE_TYPE(ref));
>
> ? ?tree __struct_access_0 = build3(COMPONENT_REF, TREE_TYPE(__struct_field0),
> ref, __struct_field0, NULL_TREE);
>
> ? ?tree modify_att_tree0 = build2(MODIFY_EXPR, TREE_TYPE(__struct_field0),
> __struct_access_0, build_int_cst(integer_type_node, 50));
>
> ? ?append_to_statement_list(modify_att_tree0, &func_stmts);
>
>
> // add the final return statement
>
> tree func_ret_expr = build1(RETURN_EXPR, void_type_node, NULL_TREE);
>
> append_to_statement_list(func_ret_expr, &func_stmts);
>
>
> // bind and gimplification
>
> DECL_SAVED_TREE(operation) = build3(BIND_EXPR, void_type_node, NULL_TREE,
> func_stmts, __func_art_block);
>
>
> // pass to middle end
>
> gimplify_function_tree(operation);
> cgraph_node(operation);
> cgraph_finalize_function(operation,false);
>
>
> did I miss something ?
>
> thank you very much
>
> Asma
>


To be fair it could be a problem with the gcc sources your compiling
with that was maybe fixed in the next commit or something. I remember
having a problem like that before but then in my repository i just
added the gcc git mirror and did:

git add remote gcc git://gcc.gnu.org/git/gcc.git
git fetch gcc
git merge gcc/master

And make clean && make

And it worked fine, i cant see any immediate error, as it already
compiles with O0 i assume.

--Phi