Will GCC eventually support SSE2 or SSE4.1?

[Nicholas Vinson]

On 5/26/23 08:42, Stefan Kanthak wrote:
>
> I could have added PROPERLY, because that's where it CLEARLY fails, as
> shown by the generated unoptimised code.

 From what I've seen so far, I find your arguments unconvincing.

In this thread alone, you've proven that you don't know how to properly 
control gcc via its command-line flags, and that you don't know how to 
properly generate assembly code for your own C example (properly in this 
case meaning to exhibit the behavior the ISO C standard requires) which 
makes it hard for me to accept your claims at face value (your C example 
is also logically incorrect, but that's not important to this discussion).

That said assuming that your "optimized assembly" examples (with the 
exception of the first) are correct, all you've done is shown that your 
versions are slightly smaller in both instruction count and size and 
declared your examples "proper". The optimization flag -O3 (like most of 
the -On flags) optimize for speed over all else, and it has been proven 
that the faster code isn't necessarily the code with fewer instructions 
or the smallest size (see the RISC v CISC debate).

To accept that your suggestions are the proper ways to generate code 
using SSE4.1 instructions at -O3, I insist on data that clearly 
demonstrates that your suggestions are at least as performant than what 
GCC's currently does.