Re: [PATCH, PR 67133] Always change gimple fntype in cgraph_edge::redirect_call_stmt_to_callee

[Richard Biener <richard dot guenther at gmail dot com>]

On Mon, Aug 17, 2015 at 3:47 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> Hi,
>>
>> even though PR 67133 has been avoided by a different patch, I believe
>> the patch below is the correct fix.  It modifies the function that
>> changes call statements according to call graph edges so that it
>> changes the fntype of the call statements also when
>> combined_args_to_skip is NULL.  This code path is taken for example
>> when a call is redirected to __builtin_unreachable and then the type
>> of the callee function is likely to mismatch with fntype of the
>> statement, which can confuse the compiler later on.
>>
>> If we agree it is a good idea, I'd like to also propose a patch
>> making the gimple verifier check whether fntypes of direct call
>> statements match the types of the callee (or at least that they have
>> the same number of same-typed arguments).
>>
>> The patch has been bootstrapped and tested on x86_64-linux, the
>> testcase is already checked in.  OK for trunk?
>>
>> Thanks,
>>
>> Martin
>>
>>
>> 2015-08-17  Martin Jambor  <mjambor@suse.cz>
>>
>>       PR middle-end/67133
>>       * cgraph.c (redirect_call_stmt_to_callee): Set gimple call fntype also
>>       when redirecting without removing any parameters.
>
> This makes sense in the case of __builtin_unreachable.  I wonder if we have
> some problems in cases where LTO or indirect call code places in incompatible
> declaration.
>
> Patch is fine with me, but I would like Richi to have final word on this one.

I don't like it too much - you'll scribble over users ABI choice here.
It's better
to guard inspectors of the call properly to _not_ expect actual arguments
according to the ABI.

Richard.

> Honza
>>
>> diff --git a/gcc/cgraph.c b/gcc/cgraph.c
>> index 22a9852..5e5b308 100644
>> --- a/gcc/cgraph.c
>> +++ b/gcc/cgraph.c
>> @@ -1461,6 +1461,7 @@ cgraph_edge::redirect_call_stmt_to_callee (void)
>>      {
>>        new_stmt = e->call_stmt;
>>        gimple_call_set_fndecl (new_stmt, e->callee->decl);
>> +      gimple_call_set_fntype (new_stmt, TREE_TYPE (e->callee->decl));
>>        update_stmt_fn (DECL_STRUCT_FUNCTION (e->caller->decl), new_stmt);
>>      }
>>