[Interest] good-compromise compatibility setting for -march=??? option (x86)?

[Thiago Macieira]

On Monday, 20 July 2020 21:50:45 PDT Rainer Wiesenfarth wrote:
> René would like to know how to set "march" when he *compiles code on* the
> Celeron (N3150) that should *run on* the (probably first generation) Core
> i7 mobile.

Oh? I had not understood that. But I was wondering why he was asking about 
i7... there's no Atom that is marketed as i7.

Let me reread...

Sorry, I was confused then! René is looking for the maximum common denominator 
between a Silvermont and a SandyBridge.

From some work I've been preparing to send to Qt:

# Architecture  Based on        New features
  # Core line
arch=Core2      x86_64  sse3,ssse3,cx16
arch=NHM        Core2   sse4.1,sse4.2,popcnt
arch=WSM        NHM
arch=SNB        WSM     avx
arch=IVB        SNB     f16c,rdrnd,fsgsbase
arch=HSW        IVB     avx2,fma,bmi,bmi2,lzcnt,movbe
arch=BDW        HSW     adx,rdseed
[...]
  # Atom line
arch=SLM        WSM     rdrnd,movbe
arch=GLM        SLM     fsgsbase,rdseed,lzcnt,xsavec,xsaves

So the common denominator of SLM and SNB is the WSM (Westmere).

Not coincidentally, it's the default -march= for GCC and Clang on Clear Linux, 
as well as what all binaries in /usr/bin and /usr/lib64 are compiled towards.

Other combinations may not match an exact CPU, like:

SLM & IVB = WSM + rdrnd
SLM & HSW = SLM
GLM & HSW = SLM + fsgsbase
GLM & BDW = SLM + fsgsbase + rdseed

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel DPG Cloud Engineering