Online Compilers and __cpuid

Here is some very minimal code I wrote that gets your (x86) processor’s brand name using the cpuid instruction.

#include <cpuid.h>
#include <cstdio>
#include <cstdint>

int main()
{
	uint32_t Name[4];
	for( uint32_t i = 2; i < 5; )
	{
		__cpuid(0x80000000 | i++, Name[0], Name[1], Name[2], Name[3]);
		fwrite(Name, 16, 1, stdout);
	}
}

main:
        push    rbp
        mov     ebp, 2
        push    rbx
        sub     rsp, 24
.L2:
        mov     eax, ebp
        mov     esi, 16
        add     ebp, 1
        mov     rdi, rsp
        or      eax, -2147483648
   >>>> cpuid

        mov     DWORD PTR [rsp+8], ecx
        mov     rcx, QWORD PTR stdout[rip]
        mov     DWORD PTR [rsp+12], edx
        mov     edx, 1
        mov     DWORD PTR [rsp], eax
        mov     DWORD PTR [rsp+4], ebx
        call    fwrite
        cmp     ebp, 5
        jne     .L2
        add     rsp, 24
        xor     eax, eax
        pop     rbx
        pop     rbp
        ret

Sample one-liner output:

% echo "I2luY2x1ZGUgPGNwdWlkLmg+CiNpbmNsdWRlIDxjc3RkaW8+CiNpbmNsdWRlIDxjc3RkaW50PgppbnQgbWFpbigpe3VpbnQzMl90IE5bNF07Zm9yKHVpbnQzMl90IGk9MjtpPDU7KXtfX2NwdWlkKDB4ODAwMDAwMDAgfCBpKyssIE5bMF0sIE5bMV0sIE5bMl0sIE5bM10pO2Z3cml0ZShOLCAxNiwgMSwgc3Rkb3V0KTt9fQ==" | base64 -d | g++ -x c
++ - -o cpu-name

% ./cpu-name 
Intel(R) Core(TM) i9-7900X CPU @ 3.30GHz

Seems fun enough, but what if we run it on those online compilers like onlinegdb.com ?

Cool! onlinegdb.com ’s “run code” instance is running off of an AMD EPYC 7501 . In some cases, I get an unspecified Intel(R) Xeon(R) CPU @ 2.30GHz, probably due to it running upon some kind of virtualized instance.

Here’s some others:

cpp.sh is running off of an Intel(R) Xeon(R) CPU W3520 @ 2.67GHz

repl.it is Intel(R) Xeon(R) CPU @ 2.30GHz(virtualized)

ideone is Intel(R) Xeon(R) CPU E3-1270 V2 @ 3.50GHz

codechef is Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz

Wow. This kinda surprised me. An in-the-wild instance of a pretty-recent Xeon with AVX-512 and everything!

Wandbox is Intel Xeon E312xx (Sandy Bridge)

rextester is Intel(R) Xeon(R) CPU E5-2640 v3 @ 2.60GHz

paiza.io is Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz

Another AVX-512 chip out in the wild

tutorialspoint is Intel(R) Xeon(R) CPU E5-2620 v4

jdoodle is Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz

coliru is AMD Opteron(tm) Processor 4332 HE

codiva is Intel(R) Xeon(R) CPU E5-2676 v3 @ 2.40GHz

GeeksForGeeks is Intel(R) Xeon(R) Platinum 8259CL CPU @ 2.50GHz

First time seeing a Cascade Lake server out in the wild.

TIO - Try It Online is Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz

Another AVX-512 chip

Lots of Xeon chips are still out in the wild, and surprisingly some of them even have AVX-512. Reason why I point this out is that AVX-512 code is not very accessible hardware at the moment outside of expensive Xeons, i9s, or their recent push into Laptops/Mobile so you can “““rent””” this remote hardware now to get a feel for the new SIMD ISA and see how it runs on these chips and “benchmark” code for yourself without having to pay $2450 on a chip.