If order(concurrent) clause is specified, then the iterations of SIMD loop can be executed concurrently.
This patch adds support for LLVM IR codegen via OMPIRBuilder for SIMD loop with order(concurrent) clause. The functionality added to OMPIRBuilder is similar to the functionality implemented in CodeGenFunction::EmitOMPSimdInit.
I think this belongs into llvm/include/llvm/Frontend/OpenMP/OMPConstants.h either explicitly or via the llvm/Frontend/OpenMP/OMPKinds.def logic.