diff --git a/Building.md b/Building.md index b04aad3dfc..a512b629ac 100644 --- a/Building.md +++ b/Building.md @@ -65,10 +65,17 @@ correct path to your cuQuantum installation by setting the environment variable ## Building CUDA Quantum with a custom LLVM version -CUDA Quantum is intended to be built using the LLVM commit that the submodule is -set to. If you need to update the LLVM commit, or if you are not using the -pre-built version of that commit in our development container, LLVM will need to -be built from source. To configure our build scripts, please set the LLVM +CUDA Quantum is intended to be built using the LLVM commit that the submodule +is set to (currently LLVM 16.0.6). If you need to update the LLVM commit, or if +you are not using the pre-built version of that commit in our development +container, LLVM will need to be built from source. ***Building with LLVM >= +17.x is not currently supported*** due to the QIR specification's requirement +to use typed pointers. LLVM 17.x removed the ability to use typed pointers and +instead now requires [opaque pointers](https://llvm.org/docs/OpaquePointers.html#version-support). +The QIR specification will be updated to support opaque pointers in the near +future. + +To configure our build scripts with a custom LLVM, please set the LLVM submodule to the desired commit, and set the following environment variable, replacing `` with the path where the freshly built LLVM tools and libraries should be installed: