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Date: Tue, 31 Jul 2018 09:25:00 -0000
From: Jan Hubicka <hubicka@ucw.cz>
To: Martin =?iso-8859-2?Q?Li=B9ka?= <mliska@suse.cz>
Cc: gcc-patches@gcc.gnu.org, Nathan Sidwell <nathan@acm.org>
Subject: Re: [PATCH] Add malloc predictor (PR middle-end/83023).
Message-ID: <20180731092546.GG29444@kam.mff.cuni.cz>
References: <b712ea25-3795-65fb-db50-d95a58889dd0@suse.cz>
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> Hi.
> 
> Following patch implements new predictors that annotates malloc-like functions.
> These almost every time return a non-null value.
> 
> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
> 
> Ready to be installed?
> Martin
> 
> gcc/ChangeLog:
> 
> 2018-07-26  Martin Liska  <mliska@suse.cz>
> 
>         PR middle-end/83023
> 	* predict.c (expr_expected_value_1): Handle DECL_IS_MALLOC
>         declarations.
> 	* predict.def (PRED_MALLOC_NONNULL): New predictor.
> 
> gcc/testsuite/ChangeLog:
> 
> 2018-07-26  Martin Liska  <mliska@suse.cz>
> 
>         PR middle-end/83023
> 	* gcc.dg/predict-16.c: New test.

These are two conceptually different things - wether you return new memory
and whether the return value is commonly non-null. While it goes together
for majority of malloc function I wonder if this is safe WRT the auto-detected
malloc attributes.  I do not know how common is code that returns new memory
only under some conditions?  

Honza