Based on what I see on [Stack Overflow](https://stackoverflow.com/a/51908785), it's recognized by all the major compilers

The [Microsoft Compiler help](https://docs.microsoft.com/en-us/cpp/intrinsics/x86-intrinsi...) includes it in the "x86 intrinsics list".

I've just compiled with success, for testing purposes, on an AMD processor.

C, relevant section:

    #include <immintrin.h>

    void test() {
        _mm_pause();
    }

Output ASM, relevant section:

    test:
    .LFB4006:
      .cfi_startproc
      endbr64
      pushq %rbp
      .cfi_def_cfa_offset 16
      .cfi_offset 6, -16
      movq  %rsp, %rbp
      .cfi_def_cfa_register 6
      rep nop
      nop
      nop
      popq  %rbp
      .cfi_def_cfa 7, 8
      ret
      .cfi_endproc
    .LFE4006:
      .size test, .-test
      .globl  main
      .type main, @function

It should be the `rep nop`.

Including `ammintrin.h` yields the same `rep nop`.

By “Intel” I really meant “x86” :P Is there an ARM compiler that recognizes it?

Unlikely, intrinsics are CPU, and sometimes CPU model, specific. Compiler builtins will instead use the intrinsic if it's available/suitable or generate equivalent code if it's not.

Ah! Sorry for that; I have no idea.

It seems that at least some ARMs have [timers that can be used](https://electronics.stackexchange.com/q/450971), which is a different strategy, but still more appropriate (I suppose).