[cfe-dev] [RFC] Support synchronisation scope in Clang atomic builtin functions

[Liu, Yaxun (Sam) via cfe-dev]

OpenCL 2.0 atomic builtin functions have a scope argument which is ideally represented as synchronization scope argument in LLVM atomic instructions.

Clang supports translating Clang atomic builtin functions to LLVM atomic instructions. However it currently does not support synchronization scope of LLVM atomic instructions. Without this, users have to use LLVM assembly code to implement OpenCL atomic builtin functions.

I have a patch (https://reviews.llvm.org/D28691 ) which allows Clang atomic builtin functions to accept an optional synchronization scope argument, so that they can be used to implement OpenCL atomic builtin functions.

This patch will not just benefits OpenCL. It will benefit any languages which need to generate atomic instructions with synchronization scopes. For languages not using synchronization scopes there is no functional change, since the synchronization scope argument is optional, and its default value generates the same LLVM instruction as before.

Your comments are welcome.

Thanks.

Sam

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