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The C++ and C semantics of the compare_and_swap operations actually require us to return a boolean "success" value. In LLVM terms this means a second comparison of the output of "cmpxchg" against the input desired value. However, x86's "cmpxchg" instruction sets all flags for the comparison formed, so we can skip any secondary comparison. (N.b. this isn't true for cmpxchg8b/16b, which only set ZF). rdar://problem/13201607 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210523 91177308-0d34-0410-b5e6-96231b3b80d8
Low Level Virtual Machine (LLVM) ================================ This directory and its subdirectories contain source code for the Low Level Virtual Machine, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the documentation provided in docs/ for further assistance with LLVM, and in particular docs/GettingStarted.rst for getting started with LLVM and docs/README.txt for an overview of LLVM's documentation setup. If you're writing a package for LLVM, see docs/Packaging.rst for our suggestions.