[clang] [llvm] [AArch64] Add __hvc, __svc and _InterlockedCompareExchangePointer_nf MS intrinsics (PR #202582)

[Adhemerval Zanella via llvm-commits]

zatrazz wrote:

I followed the MSVC intrisinc more closely now, and checked using 19.51.36244 for ARM64:

* Intrinsics llvm.aarch64.{svc,hvc} are now i64 (i32 imm, i64, i64, i64, i64) — a value-returning, non-variadic signature. Unused register slots are passed as undef.
* Lowering (LowerINTRINSIC_W_CHAIN) models it as a small call: copy the provided args into X0–X3, emit an AArch64ISD::SVC/HVC node with a caller-saved clobber mask, and read the result from X0. undef operands are skipped, so codegen is byte-identical to what cl emits.
* Sema limits the builtin to ≤5 arguments; CodeGen widens each arg to 64-bit and truncates the X0 result to unsigned int (matching the MSVC prototype).

https://github.com/llvm/llvm-project/pull/202582