[PATCH] D123665: [SimplifyLibCalls] Don't mark memchr() memory as fully dereferenceable

[Nikita Popov via Phabricator via llvm-commits]

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C11 specifies memchr() as follows:

> The memchr function locates the first occurrence of c (converted to an unsigned
> char) in the initial n characters (each interpreted as unsigned char ) of the object
> pointed to by s. The implementation shall behave as if it reads the characters sequentially
> and stops as soon as a matching character is found.

In particular, it is well-defined to specify a memchr size larger than the underlying object, as long as the character is found before the end of the object.


https://reviews.llvm.org/D123665

Files:
  llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
  llvm/test/Transforms/InstCombine/mem-deref-bytes.ll
  llvm/test/Transforms/InstCombine/memchr.ll
  llvm/test/Transforms/InstCombine/strchr-1.ll

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