Intel's New Compiler Boosts Transmeta's Crusoe

Bram Stolk writes: "Intel recently released its new C++ compiler for linux. I've been testing it on my TM5600 Crusoe. Ironically, it turns out that Transmeta's arch nemesis, Intel, provides the tools to really unlock Crusoe's full potential on linux." It doesn't support all of gcc's extensions, so Intel's compiler can't compile the Linux kernel yet, but choice is nice.

Comments

My results with Linux and NetBSD

[Walter Bell]

The Linux results were interesting, but rather flat: everything benefited from it on my system. However I rebooted into NetBSD and gave the compiler a shot at 'make sys' and 'make world'. Because the NetBSD kernel does not use any nonstandard gcc extensions, it compiled just fine with the new compiler. What I found was:

• The kernel showed a marked performance benefit on the TM5600. On my TM5400 the results were not noticable.
• Most userspace utilities appeared to be quite a bit faster on both CPUs. However, some (one notable example being /usr/local/bin/perl) were much slower with the new compiler. I verified that this was not the case on Linux, so it is unclear to me as to why this happens under NetBSD. Further investigation is needed.

~wally

This is very interesting.

[Anton Anatopopov]

It seems as if Intel is playing a very clever game here. If Intel can unlock the true potential of the transmeta's code morphing architecture, then they are giving it a great deal of credibility in the industry.

Given that Intel makes a lot of its money from selling silicon, why on earth would it develop compiler technology which legitimized the approach of one of its major competitors ?

I can only assume that Intel has some fairly advanced code morphing technology of its own, and has been using the transmeta devices as a testbed.

I can just see it now, a 4GHz pentium with code morphing extensions.

I expect this one will be fought out in the patent arena. IBM and Intel are heavyweight players and I don't see either of them giving any ground willingly.

Re:GCC extensions??

[srvivn21]

It gets significant performance improvements this way.

But are these performance increases greater than what would be realized if the Kernel could be compiled using icc?

This doesn't address the maintainence issue, but it's something that I am looking forward to seeing in the near future. I figure someone has the time and drive to hack the Kernel source to the point that icc will compile it. Goodness knows, I don't.

Not surprising

[d5w]

This isn't a particularly startling result. Many of the things an x86 compiler has to optimize for these days are similar across all processors: e.g., regular branch patterns are faster than unpredictable ones; you have very few visible registers; it's helpful to have closely associated data in the same cache lines; you're usually better with the RISCy subsets of the ISA; etc. Intel would have had to go well out of its way to optimize for their own chips and pessimize for others, and I can't see Intel bothering.

Re:KDE performance

[hexix]

I was wondering the same type of thing. Is this going to be helpful to KDE in any way?

It's my understanding that the problem is with the gnu library linker, but I don't know much about compilers. Does this intel compiler have it's own library linker or does it still use the gnu one?

If it does use it's own can we expect to see dramatic speed increases if we were to compile KDE with this intel compiler?

Re:GCC extensions??

[rgmoore]

The Kernel should not be at the mercy of one compiler.

"At the mercy of" one compiler is a rather strange description, don't you think? After all, both Linux and gcc are released under the GPL, which means that anyone who wants to use Linux will already be willing to accept what many people view as the most obnoxious feature of gcc (the license). And it's not as though the gcc developers can yank the rug out from under Linux by making it proprietary, refusing to distribute old versions, etc. If anything it would be crazy to make serious modifications to Linux to take advantage of a compiler like Intel's that could be taken away at any minute.

No kernel, so what?

[labradore]

It seems that nearly everyone has missed the point of this article. POVRay is a program that makes very heavy use of the FPU. ICC speeds up POVRay's performance by 16% to 28% in the x86 architecture compared to GCC. In other words x86 FPU's are faster executing code from programs built with ICC. The Linux kernel (and almost any kernel for that matter) has very little floating point code. Therefore one cannot assume that ICC would improve kernel performance, even if it could compile it.

The real story here is that the maintainers of GCC aught to look carefully at their optimization code for x86 FPUs.

I'm betting that Intel developers have done their best to make use of the P4 cache. Since Transmeta CPUs do work recompiling programs on the fly they have larger caches (128KB L1 + 512KB L2) than the Athlon (128KB L1 + 256KB L2) and the Pentium 4 (20? KB L1 and 256KB L2). ICC is probably also highly agressive in implimenting SSE and SSE2 instructions. Transmetal CPUs also use VLIW instructions in core wich are by their nature highly parallel (compared to native x86). Even if the Transmeta chips can't use SSE and SSE2 they may benefit from the parallel-oriented optimizations that ICC probably makes.

On a different note: in a program like POVRay that executes basically the same tight loop of instructions mega-gazillions of times during a scene the Transmeta chip's software can have the opportunity to highly optimize the program. I would like to see the stats on the second and third runs of that rendering to see how much the Transmeta "code morphing" improved the performance. It would be very interesting if the GCC and ICC built POVRays perfomed at almost the same speed after a few runs. It would obviously be a great proof of the value of Transmeta's design. I for one have always wondered what the code morphing stuff would be able to do if it were able to interface with the operating system and recompile and save the entire system back to the hard disk as it goes through the optimiztion processes. (I suppose that errors could be highly disasterous.)

That's just my $0.02 and I'm no expert so I could definately be wrong.

This is not a signature.

What about gcc 3.0 ?

[Stormie]

Interesting benchmark of Intel's compiler vs. gcc 2.95.4, but what about gcc 3.0? I'd love to see how that compared, given that I've heard such mixed opinions about whether it's optimisation tends to be better, worse, or the same as the 2.95 series..

About the Intel Compilers...

[ChaoticCoyote]

...I wrote up a short "First Look" regarding the "noncommercial" (i.e., no-cost) versions of Intel's C++ and Fortran 95 compilers for Linux. I look at licensing, too, and have Intel's comments posted as well.

You can also look at some rudimentary benchmarks comparing gcc 3.0.1 and Intel C++ 5.0.