Re: [PR78365] ICE in determine_value_range, at tree-ssa-loo p-niter.c:413

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

On Wed, Nov 23, 2016 at 4:33 PM, Martin Jambor <mjambor@suse.cz> wrote:
> Hi,
>
> On Fri, Nov 18, 2016 at 12:38:18PM +1100, kugan wrote:
>> Hi,
>>
>> I was relying on ipa_get_callee_param_type to get type of parameter and then
>> convert arguments to this type while computing jump functions. However, in
>> cases like shown in PR78365, ipa_get_callee_param_type, instead of giving
>> up, would return the wrong type.
>
> At what stage does this happen?  During analysis
> (ipa_compute_jump_functions_for_edge) or at WPA
> (propagate_constants_accross_call)?  Both?

Hmm, where does jump function compute require the callee type?
In my view the jump function should record

 (expected-incoming-type) arg [OP X]

for each call argument in its body.  Thus required conversions are
done at WPA propagation time.

>> I think the current uses of
>> ipa_get_callee_param_type are fine with this.
>>
>> Attached patch now uses callee's DECL_ARGUMENTS to get the type. If it
>> cannot be found, then I would give up and set the jump function to varying.
>
> But DECL_ARGUMENTS is not available at WPA stage with LTO so your
> patch would make our IPA layer to optimize less with LTO.  This was
> the reason to go through the hoops of TYPE_ARG_TYPES in the first
> place.
>
> If TYPE_ARG_TYPES cannot be trusted, then I'm afraid we are back to
> square one and indeed need to put the correct type in jump functions.

If DECL_ARGUMENTS is not available at WPA stage then I see no other
way than to put the types on the jump functions.

> If just preferring DECL_ARGUMENTS is enough, then changing
> ipa_get_callee_param_type to use that if is is available, as Richi
> suggested, would indeed be preferable.  But if even falling back on it
> can cause errors, then I am not sure if it helps.
>
> In any event, thanks for diligently dealing with the fallout,
>
> Martin
>
>
>>
>> Bootstrapped and regression tested on x86_64-linux-gnu with no new
>> regressions. Is this OK for trunk?
>>
>> Thanks,
>> Kugan
>>
>> gcc/testsuite/ChangeLog:
>>
>> 2016-11-18  Kugan Vivekanandarajah  <kuganv@linaro.org>
>>
>>       PR IPA/78365
>>       * gcc.dg/torture/pr78365.c: New test.
>>
>> gcc/ChangeLog:
>>
>> 2016-11-18  Kugan Vivekanandarajah  <kuganv@linaro.org>
>>
>>       PR IPA/78365
>>       * ipa-cp.c (propagate_constants_accross_call): get param type from callees
>>       DECL_ARGUMENTS if available.
>>       * ipa-prop.c (ipa_compute_jump_functions_for_edge): Likewise.
>>       (ipcp_update_vr):  Remove now redundant conversion of precision for VR.
>>       * ipa-prop.h: Make ipa_get_callee_param_type local again.