[llvm-bugs] [Bug 33190] Wrong output of isl_set_project_out()

via llvm-bugs llvm-bugs at lists.llvm.org
Mon May 29 02:54:01 PDT 2017


Michael Kruse <llvm at meinersbur.de> changed:

           What    |Removed                     |Added
         Resolution|---                         |INVALID
             Status|NEW                         |RESOLVED

--- Comment #1 from Michael Kruse <llvm at meinersbur.de> ---
> The output domain seems wrong, n shouldn't be { [] } universe. The counter cases are, when i0 is 0, n should be <= 2; when i0 is -1, if n is -1, the condition "4i0 >= -2 + n" doesn't satisfied; ...

After projecting out, the remaining [] is in the set, if there exists one i0
such that the condition is satisfied. For each n I can find an i0 such that the
condition is fulfilled, e.g. 

i0 = (n <= -2) ? -1 : [-1/2 + 1/4*n]

That is, you choose i0 after n is fixed, not the other way around.

Btw, for isl-only questions, there is a mailing list:
isl-development at googlegroups.com

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