[llvm-dev] GCC Value Range Analysis framework

[Fernando Magno Quintao Pereira via llvm-dev]

Hi,

    that's very interesting: doing the range analysis backwardly, they
get some information about variables that are not directly related by
statements, like in the example Andrew gave:

a_2 = b_1 - 20
if (a_2 < 40) {
  // we can learn information not only about a_2, but also about b_1
}

    We have a traditional implementation of range analysis in LLVM.
The code is available here
(https://homepages.dcc.ufmg.br/~fernando/classes/dcc888/assignment/src/RangeAnalysis_LLVM_38.zip)
for LLVM 3.8, and here
(https://homepages.dcc.ufmg.br/~fernando/classes/dcc888/assignment/src/RangeAnalysis_LLVM_80.zip)
for LLVM 8.0. We have described it in this paper:

Raphael Ernani Rodrigues, Victor Hugo Sperle Campos, Fernando Magno
Quintão Pereira: A fast and low-overhead technique to secure programs
against integer overflows. CGO 2013: 33:1-33:11

    I use this implementation of range analysis as a project
assignment in a course on Static Program Analysis
(https://homepages.dcc.ufmg.br/~fernando/classes/dcc888/assignment/).
I believe the implementation is pretty mature. The range analysis
works on a slightly different program representation, in which
variables are renamed after conditionals.

Regards,

Fernando

> Date: Sat, 25 May 2019 15:30:44 -0700
> From: Chris Lattner via llvm-dev <llvm-dev at lists.llvm.org>
> To: llvm-dev at lists.llvm.org
> Cc: amacleod at redhat.com
> Subject: [llvm-dev] GCC Value Range Analysis framework
> Message-ID: <1968F7EB-1E58-496E-AC8A-D02E5A373A4A at nondot.org>
> Content-Type: text/plain; charset="utf-8"
>
> Andrew MacLeod has several great posts on the GCC mailing list that describes his new ‘ranger’ framework.  I haven’t dug in deeply, but it looks like a very nicely considered approach, and solves several issues in the corresponding LLVM infra.
>
> It has been years since I’ve thought about this area - I’d be curious to know if anyone else has thought about this lately, and what you think:
>
> On-Demand range technology [1/5] - Executive Summary <https://gcc.gnu.org/ml/gcc/2019-05/msg00193.html>
> On-Demand range technology [2/5] - Major Components : How it works <https://gcc.gnu.org/ml/gcc/2019-05/msg00194.html>
> On-Demand range technology [3/5] - The Prototype <https://gcc.gnu.org/ml/gcc/2019-05/msg00195.html>
> On-Demand range technology [4/5] - Performance results <https://gcc.gnu.org/ml/gcc/2019-05/msg00196.html>
> On-Demand range technology [5/5] - Looking to the future. <https://gcc.gnu.org/ml/gcc/2019-05/msg00197.html>
>
> -Chris