[clang] [llvm] [clang][RISCV] Use macro to check if intrinsics are supported (PR #187197)

[Craig Topper via cfe-commits]

================
@@ -0,0 +1,29 @@
+==============
+RISC-V Support
+==============
+
+.. contents::
+   :local:
+
+Intrinsic Detection Macros
+===========================
+
+Clang provides macros to detect which RISC-V intrinsics are supported by the
+toolchain.
+Note: This is independent from assembler support.
+
+Scalar/Vector Intrinsic Detection
+---------------------------
+
+Macros of the form ``__riscv_intrinsic_<extension>`` indicate that the
+toolchain supports scalar/vector built-in functions for a given extension:
----------------
topperc wrote:

`built-in functions` -> `intrinsics`

https://github.com/llvm/llvm-project/pull/187197