Fwd: About the names of CPUs and architectures

[Magnus Ihse Bursie]

I tried to send this a few days ago, but it seems like it never reached 
the list..? Weird; I'm trying to resend it. Sorry if it's a dupe.

*The background
*
Currently, there is a lot of different names floating around in the 
build system for the same piece of hardware, especially regarding Intel 
architecture. This is not just our fault, there is no complete 
world-wide industry consensus.

For the 32-bit Intel CPU, we have:
x86, i386, i586 and ia32.

For the 64-bit Intel CPU, we have:
x86_64, amd64 and x64.

Fredrik wanted to unite this as much as possible. Unfortunately, he did 
so by introducing new names that was not used before (ia32 and x64). 
Currently, these show up mainly in how the configurations are named (the 
directories under build/). While the new names might have their merits, 
I believe they are not as commonly used as the old names. I also believe 
not much is gained by introducing a new name.

As a reference, configure is consistently using the name x86_64 for the 
64-bit Intel architecture, but switches between i386 and i586 depending 
on OS (and, of course, how antique the CPU is).

In the OpenJDK source code, the 64-bit architecture was previously 
relatively consistently named amd64, but recently this platform has been 
renamed x86_64 -- but only on macosx. This is an even more unfortunate 
situation, that we have different names internally for the same CPU 
depending on OS. We should really be able to avoid this.

The 32-bit architecture has been most commonly refered to as i586, but 
there is really no clear winner between i586 and i386.

On top of this is the difference between "cpu" and "cpu architecture", 
where the former specifices a specific cpu with a given address length 
(e.g. x86_64) and the latter a family of cpu:s with different address 
lengths (e.g. x86 and x86_64). Currently we support two such familys, 
the sparc family and the Intel family. In the current build-infra 
solution they are named "sparc" and "x86", respectively.

*My proposal*

I propose that we change our new default names to:
32-bit Intel: x86
64-bit Intel: x86_64
Intel arctitecture: x86

(As reference:
32-bit Sparc: sparc
64-bit Sparc: sparcv9
Sparc architecture: sparc)

Rationale:
x86_64 seems like the easy choice. It matches the configure name, and 
the new macosx name. Appearantly it was important for macosx to change 
this, so we should try to move the rest of the product this was. It also 
matches other large open source projects like Linux.
"amd64" seems a bit old-fashioned, and "x64" is more common in marketing 
than in development projects.

x86 is trickier. It is possible to argue for i586 instead, since it 
matches configure (sometimes) and the old name (sometimes). However, it 
feels like it is a superset of i386 and that it opens up for the 
possibility to be able to choose i386 instead, when that really is not 
an option. Also, I believe it would create a more coherent system of cpu 
and cpu architecture naming, corresponding to the sparc world (and 
possibly other future cpu architectures like arm (arch)/arm 
(32-bit)/arm64). I won't fight to defent this name, though, so if I'm 
voted down I'll accept that. :-)

Furthermore, I'd like to change the source so we use the new names as 
far as just possible. In the places where it is not possible (basically, 
where it will affect visible parts of the resulting product, like 
directory names or os.arch property), we should have a simple mapping 
table replacing the names that needs replacing.

Unfortunately, I'm leaving for vacation/parental leave today, and won't 
be able to implement any changes. Jonas and Erik might do that, but 
stated that there is "no promises".

But at least it would be good to hear your opinions. I hope we don't get 
as an infected debate as with the build/target issue; let's keep this 
one civilized ;-)

/Magnus