Nikita Popov 27392a35ef [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.

2024-05-23 15:14:34 +02:00

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