[all-commits] [llvm/llvm-project] 27392a: [SCCP] Don't allow undef ranges when performing op...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 27392a35ef052aa515f38359de89aced11a4363d
      https://github.com/llvm/llvm-project/commit/27392a35ef052aa515f38359de89aced11a4363d
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2024-05-23 (Thu, 23 May 2024)

  Changed paths:
    M llvm/lib/Transforms/Utils/SCCPSolver.cpp
    M llvm/test/Transforms/SCCP/ip-add-range-to-call.ll
    M llvm/test/Transforms/SCCP/range-with-undef.ll

  Log Message:
  -----------
  [SCCP] Don't allow undef ranges when performing operations (#93163)

When performing some range operation (e.g. and) on a constant range that
includes undef, we currently just ignore the undef value, which is
obviously incorrect. Instead, we can do one of two things:
 * Say that the result range also includes undef.
 * Treat undef as a full range.

This patch goes with the second approach -- I'd expect it to be a bit
better overall, e.g. it allows preserving the fact that a zext of a
range with undef isn't a full range.

Fixes https://github.com/llvm/llvm-project/issues/93096.



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