[clang] [NFC] Cleanup and sort hlsl_intrinsics.h (PR #72414)

[via cfe-commits]

================
@@ -11,557 +11,614 @@
 
 namespace hlsl {
 
-__attribute__((availability(shadermodel, introduced = 6.0)))
-__attribute__((clang_builtin_alias(__builtin_hlsl_wave_active_count_bits))) uint
-WaveActiveCountBits(bool bBit);
+// Note: Functions in this file are sorted alphabetically, then grouped by base
+// element type, and the element types are sorted by size, then singed integer,
+// unsigned integer and floating point. Keeping this ordering consistent will
+// help keep this file manageable as it grows.
 
+#define _HLSL_BUILTIN_ALIAS(builtin)                                           \
----------------
philnik777 wrote:

Yes, this is definitely a reserved identifier. Anything with two underscores in the name and anything starting with an underscore and upper letter is reserved. There are also some more complicated rules, but that's not relevant here.

https://github.com/llvm/llvm-project/pull/72414