clang/docs/RISCVSupport.md

# RISC-V Support

```{contents}
:local: true
```

## Intrinsic Detection Macros

Clang provides macros to detect which RISC-V intrinsics are supported by the
toolchain. This is only available if intrinsics are ratified, in other word,
experimental intrinsics do not have macro defined.
Note: This is independent from assembler support.

### Intrinsic Detection

Macros of the form `__riscv_intrinsic_<extension>` indicate that the toolchain
supports intrinsics for a given extension:

```c
#if defined(__riscv_intrinsic_zbb)
  // Toolchain supports Zbb scalar intrinsics like __riscv_orc_b_*
  // These can be used with target attributes even if -march doesn't include Zbb
  __attribute__((target("arch=+zbb")))
  unsigned long process_with_zbb(unsigned long x) {
    return __riscv_orc_b_64(x);
  }
#endif
```

Composite extensions are also defined when all their sub-extensions are available, e.g.

: `__riscv_intrinsic_zkn` - zbkb + zbkc + zbkx + zkne + zknd + zknh