Intel® C++ Compiler 16.0 User and Reference Guide
This topic only applies to Intel® 64 and IA-32 architectures targeting Intel® Graphics Technology.
You can write functions that you intend to run on a target, and sections of offloaded code, to take advantage of target-specific intrinsic functions.
When the compiler generates code for the processor graphics, it defines the macro __GFX__. You can write target-specific code within an #ifdef __GFX__ section.
Do not use the __GFX__ macro inside the statement following a #pragma offload statement. You can, however, use this macro in a subprogram called from the pragma.