Nikita Popov a2ccd5d88f [FunctionAttrs] Fix incorrect noundef inference with poison attrs (#89348) ...

Currently, when inferring noundef, we only check that the return value
is not undef/poison. However, we fail to account for the possibility
that a poison-generating return attribute will convert the value to
poison, and then violate the noundef attribute, resulting in immediate
UB.

For the relevant return attributes (align, nonnull and range), check
whether we can trivially re-prove the relevant property, otherwise do
not infer noundef.

This fixes the FunctionAttrs side of
https://github.com/llvm/llvm-project/issues/88026.

2024-04-23 14:26:12 +09:00

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