Intel Compiler /QxCORE-AVX2 switch and compatibility with AMD Excavator/RyZen

Question

For some unknown reason Intel decided to does not support AVX2 via typical /arch: option. /arch: recognizes only following instructions IA32,SSE,SSE2,SSE3,AVX. So if you want to compile for AVX2 you are basically forced to activate /QxCORE-AVX2 switch. The problem with this option is that it injects check code. That code at runtime checks if your cpu is compatible with selected intructions. If CPU is not compatible then this message pops-up.

Please verify that both the operating system and the processor support Intel(R) MOVBE, F16C, FMA, BMI, LZCNT and AVX2 instructions.

Now I'm worried that the same message may pop-up on AMD Excavator and RyZen CPU due to not being GenuineIntel. Unfortunately I do not have access to any AMD cpu so I can't check that on real cpu. To make your life easier I've compiled this simple code with activated /QxCORE-AVX2 option.

#include "stdafx.h"


int _tmain(int argc, _TCHAR* argv[])
{
    double a, b, c;
    a = 3.0;
    b = 2.0;
    c = 1.0;

    a = a*b + c;

    printf("a=%1.1f",a);

    return 0;
}

and here is decompiled asm code: http://codepad.org/KL4Vq978

My question to people who understand asm code is do you see anything what may block execution of this code on latest AMD cpus? If yes will this http://www.softpedia.com/get/Programming/Patchers/Intel-Compiler-Patcher.shtml help?

Answer 1

It turns out that /arch:CORE-AVX2 is recognized and compiled executable contains FMA instructions! I really do not understand why this option is not listed in Visual Studio and in ICL /help ?!?

Dropbox menu in Visual Studio (NO AVX2!) http://i.cubeupload.com/c1xidV.png

ICL /help http://i.cubeupload.com/y2Cre6.png

Answer 2

The Ryzen supports these instruction sets, but the code will not run on AMD processors because it checks if the processor is "GenuineIntel". There has been a long discussion and legal battle about this issue. See http://www.agner.org/optimize/blog/read.php?i=49