[PATCH] D91979: [Clang][Attr] Introduce the `assume` function attribute

[Johannes Doerfert via Phabricator via cfe-commits]

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The `assume` attribute is a way to provide additional, arbitrary
information to the optimizer. For now, assumptions are restricted to
strings which will be accumulated for a function and emitted as comma
separated string function attribute. The key of the LLVM-IR function
attribute is `llvm.assume`. Similar to `llvm.assume` and
`__builtin_assume`, the `assume` attribute provides a user defined
assumption to the compiler.

A follow up patch will introduce an LLVM-core API to query the
assumptions attached to a function. We also expect to add more options,
e.g., expression arguments, to the `assume` attribute later on.

The `omp [begin] asssumes` pragma will leverage this attribute and
expose the functionality in the absence of OpenMP.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91979

Files:
  clang/docs/LanguageExtensions.rst
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/lib/CodeGen/CGCall.cpp
  clang/lib/Sema/SemaDeclAttr.cpp
  clang/test/CodeGen/assume_attr.c
  clang/test/CodeGenCXX/assume_attr.cpp

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