[all-commits] [llvm/llvm-project] a2ccd5: [FunctionAttrs] Fix incorrect noundef inference wi...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a2ccd5d88ffa8a730914c608601e1e3f7785cb08
      https://github.com/llvm/llvm-project/commit/a2ccd5d88ffa8a730914c608601e1e3f7785cb08
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2024-04-23 (Tue, 23 Apr 2024)

  Changed paths:
    M llvm/lib/Transforms/IPO/FunctionAttrs.cpp
    M llvm/test/Transforms/FunctionAttrs/noundef.ll

  Log Message:
  -----------
  [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.



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