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Re: [RFC] UBSan unsafely uses VRP

From: Yury Gribov <y dot gribov at samsung dot com>
To: Jakub Jelinek <jakub at redhat dot com>, Marat Zakirov <m dot zakirov at samsung dot com>
Cc: GCC Mailing List <gcc at gcc dot gnu dot org>, Richard Biener <richard dot guenther at gmail dot com>
Date: Wed, 12 Nov 2014 11:42:39 +0300
Subject: Re: [RFC] UBSan unsafely uses VRP
Authentication-results: sourceware.org; auth=none
References: <5462170F dot 5040102 at samsung dot com> <20141111141521 dot GE5026 at tucnak dot redhat dot com>

On 11/11/2014 05:15 PM, Jakub Jelinek wrote:

There are also some unsafe code in functions
ubsan_expand_si_overflow_addsub_check, ubsan_expand_si_overflow_mul_check
which uses get_range_info to reduce checks number. As seen before vrp usage
for sanitizers may decrease quality of error detection.


Using VRP is completely intentional there, we don't want to generate too
slow code if you decide you want to optimize your code (for -O0 VRP isn't
performed of course).

On the other hand detection quality is probably more important thanimportant regardless of optimization level. When I use a checker, Idon't want it to miss bugs due to overly aggressive optimization.

I wish we had some test to check that sanitizer optimizations are indeedconservative.

-Y

Follow-Ups:
- Re: [RFC] UBSan unsafely uses VRP
  - From: Marek Polacek

References:
- [RFC] UBSan unsafely uses VRP
  - From: Marat Zakirov
- Re: [RFC] UBSan unsafely uses VRP
  - From: Jakub Jelinek

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