[PATCH] D128939: [InstCombine] Fold memchr and strchr equality with first argument

[Martin Sebor via Phabricator via llvm-commits]

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This change enhances `memchr` and `strchr` handling to simplify calls to the functions used in equality expressions with the first argument to at most two integer comparisons:

- `memchr(A, C, N) == A` to `N && *A == C` for either a dereferenceable `A` or a nonzero `N`,
- `strchr(S, C) == S` to `*S == C` for any `S` and `C`, and
- `strchr(S, '\0') == 0` to `true` for any `S`


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D128939

Files:
  llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
  llvm/test/Transforms/InstCombine/memchr-11.ll
  llvm/test/Transforms/InstCombine/memrchr-8.ll
  llvm/test/Transforms/InstCombine/strchr-4.ll

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