GCC 9 Guts Out The PowerPC SPE Support

[phoronix]

Phoronix: GCC 9 Guts Out The PowerPC SPE Support

It should come as no surprise since it was deprecated in this year's GCC 8 release, but the PowerPC SPE code has been removed...

http://www.phoronix.com/scan.php?pag...ves-PowerPCSPE

[cb88]

Derp: the SPE acronym apparently has 2 different meanings as jabl called me out on below.

[jabl]

SPE stands for Synergistic Processing Element... its basically a regular PPC core called an PSU with a special memory controller called an MFC designed for it to operate out of a local scratch memory but still with access to the main memory bus for receiving and completing work. It's not really a "signal processor" like a DSP, its just a regular generic core with no branch prediction relying on the compiler to arrange the code so that it executes the common case most often (a good strategy for simplicity and power usage, but not for absolute peak performance). That said a lot of amazing games were built on top of those SPEs hard to program for but very powerful when used properly.

From https://wiki.debian.org/PowerPCSPEPort :

"PowerPC SPE" refers to the "Signal Processing Engine" hardware present on low-power 32-bit ?FreeScale and IBM "e500" cores. If you wish to run Debian on a PS3 or other IBM-Cell-based system, you should instead use the standard powerpc port. The "SPE" in the "powerpcspe" architecture does not refer to the "Synergistic Processing Element" units on IBM Cell microprocessors, although both are PowerPC variants. See also http://lists.debian.org/debian-devel.../msg00592.html

[cb88]

From https://wiki.debian.org/PowerPCSPEPort :

Well *that* isn't confusing as all get out...

[ssokolow]

Interesting coincidence that Rust's platform support list quietly gained a powerpc-unknown-linux-gnuspe target for one of the meanings of SPE relatively recently. (I didn't have time to dig deep to track down when, but I don't remember it being there last time I had reason to check.)

[FireBurn]

Are those the SPE's found in the PS3?

[monraaf]

This isn't to be confused with conventional POWER/PowerPC but rather PowerPC SPE that is for the "Signal Processing Engine" on older FreeScale/IBM cores like the e500. It's not all that important these days and doesn't affect newer versions of the 64-bit Power support.

Funny enough, support for the PowerPCSPE target in LLVM was just recently improved so much that it's actually possible to use Rust on this architecture.

Heck, Phoronix even reported about that: https://www.phoronix.com/scan.php?pa...ebian-14-Archs

And what Michael missed is that there is still a gcc maintainer working on the port, so it is eventually coming back: https://gcc.gnu.org/ml/gcc-patches/2.../msg00592.html