Re: Itanium support is back in GCC 15

On Mon, 24 Feb 2025 15:08:57 -0500
Arne Vajhøj <arne@vajhoej.dk> wrote:

On 2/24/2025 12:42 PM, Michael S wrote:

On Thu, 7 Nov 2024 16:48:49 -0500
Arne Vajhøj <arne@vajhoej.dk> wrote: 

On 11/7/2024 12:33 PM, gcalliet wrote: 

Le 04/11/2024 à 21:16, Arne Vajhøj a écrit : 

I wish someone would volunteer to create VMS support
in GCC 16 or whatever!
   

Because I created (canadian method) Gnat Ada (on gcc) for VMS
Itanium, and because we were on gcc 4.7, there is some work ahead,
but why not :)
>
The big issue is the step to gcc 5, where they upgraded to c++
mode. It is one of the reasons why Adacore didn't continue support
of gnat ada on VMS in 2015. 

>
VMS x86-64 has a better C++ compiler than VMS Itanium. 

 
That comment was about C++ standard compliance not performance.
 

Ok

C++ VMS x86-64 is clang which in the (older) clang version used
should mean C++14 while C++ VMS Itanium is very very old (like
C++ 98 old).
 

According to the benchmarks that you posted here several months (a
year?) ago, VMS x86-64 compilers are quite awful comparatively to
x86-64 compilers available on Windows/Linux/BSD.
Do you want to say that VMS Itanium compilers are worse? 

 
I believe the conclusion was that the VMS x86-64 compilers except C++
was slower than C/C++ on other OS and C++ on VMS.
 

Somehow I got an impression that C++ compilers were also significantly
slower than C++ compilers on other platforms.
Do I misremember?

My guess is that it is a combination of the GEM to LLVM translation
and a desire from VSI to be a little conservative (prioritizing
correctness over speed).
 
Arne