__riscv_arch_test
In this section:
Description
An integer that is set to 1 when the compiler supports architecture extension test macros. The value of an architecture extension test macro is computed based on its version number, using this formula:
major_v * 1000000 + minor_v * 1000 + revision_v
Example
If the F extension is version 2.2, __riscv_f is defined to 2002000.
If the B extension is version 0.92, __riscv_b is defined to 92000.