[llvm-bugs] [Bug 27067] New: [Polly] Exploit undefined behavior of out-of-bound accesses in C/C++

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27067

            Bug ID: 27067
           Summary: [Polly] Exploit undefined behavior of out-of-bound
                    accesses in C/C++
           Product: Polly
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Optimizer
          Assignee: polly-dev at googlegroups.com
          Reporter: tobias at grosser.es
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 16091
  --> https://llvm.org/bugs/attachment.cgi?id=16091&action=edit
Example with signed check

In case an __assume statement is within a Scop, we do not yet exploit the
properties it describes.

A use case for this would to pass out-of-bound information for C arrays to
LLVM-IR. In C, accesses that leave the bounds of a defined array are undefined
behavior. Consequently, we can use this information to simplify our context /
run-time checks.

It should be easy to teach our assumption tracking to exploit such expressions,
assuming the conditions we look at are signed (example attached).

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