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Why is Rosetta 2 fast?

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Re: Why is Rosetta 2 fast?

#321

Post by Luke-Jr »

spijdar wrote: post #250
GeekyBear wrote: post #192

Earlier quoted context omitted.

> It was originally a startup, but had been bought by IBM by the time Apple was interested. Rosetta shipped in 2005. IBM bought Transitive in 2008. The last version of OS X that supported Rosetta shipped in 2009. I always wondered if the issue was that IBM tried to alter the terms of deal too much for Steve's taste.

A lesser known bit of trivia about this is that IBM would go on to use Transitive's technology for the exact opposite of Rosetta -- x86 to PowerPC translation, in the form of "PowerVM Lx86", released that year (2008). It's very fascinating to me, since IBM appears to have extended the PowerPC spec with this application specifically in mind. Up until POWER10, the Power/PowerPC ISA specified an optional feature called…

In theory, PROT_SAO should be useful for qemu, and trivial to make patches implementing there. That's assuming the kernel actually sets it, though. The problem I encountered when I set out to do it a year or so ago, was that I couldn't find a good test case to fail without it...

Re: Why is Rosetta 2 fast?

#322

Post by masklinn »

comex wrote: post #314
masklinn wrote: post #217

Earlier quoted context omitted.

> That may be true on the mach system call side, but the UNIX system calls don't appear to change. They very much do, without warning, as the Go project discovered (after having been warned multiple times) during the Sierra betas: https://github.com/golang/go/issues/16272 https://github.com/golang/go/issues/16606 That doesn't mean Apple goes outs of its way to break syscalls (unlike microsoft), but there is no suppor…

Another example: https://github.com/jart/cosmopolitan/issues/426

Nice I had not seen these.

Re: Why is Rosetta 2 fast?

#323

Post by MayeulC »

AceJohnny2 wrote: post #229
hamstergene wrote: post #123

Earlier quoted context omitted.

Could it be simply because many binaries were produced by much older, outdated optimizers. Or optimized for size. Also, optimizers usually target “most common denominator” so native binaries rarely use full power of current instruction set. Jumping from that peculiar finding to praising runtime JIT feels like a longshot. To me it’s more of an argument towards distributing software in intermediate form (like Apple Bit…

> Or optimized for size. Note that on gcc (I think) and clang (I'm sure), -Oz is a strict superset of -O2 (the "fast+safe" optimizations, compared to -O3 that can be a bit too aggressive, given C's minefield of Undefined Behavior that compilers can exploit). I'd guess that, with cache fit considerations, -Oz can even be faster than -O2.

Interesting, I didn't know about -Oz (only -Os for size). -Oz is reportedly mac-specific https://stackoverflow.com/questions/1778538/how-many-gcc-opt...

Re: Why is Rosetta 2 fast?

#324

Post by majou »

webwielder2 wrote: post #292

(Apologies for the flame war quality to this comment, I’m genuinely just expressing an observation) It’s ironic that Apple is often backhandedly complimented by hackers as having “good hardware” when their list of software accomplishments is amongst the most impressive in the industry and contrasts sharply with the best efforts of, say, Microsoft, purportedly a “software company.”

The transparent APFS migration was one heck of a feat.

Re: Why is Rosetta 2 fast?

#325

Post by kijiki »

GeekyBear wrote: post #192
kijiki wrote: post #146

Earlier quoted context omitted.

> Anyone know how they implemented PPC-to-x86 translation? They licensed Transitive's retargettable binary translator, and renamed it Rosetta; very Apple. It was originally a startup, but had been bought by IBM by the time Apple was interested.

> It was originally a startup, but had been bought by IBM by the time Apple was interested. Rosetta shipped in 2005. IBM bought Transitive in 2008. The last version of OS X that supported Rosetta shipped in 2009. I always wondered if the issue was that IBM tried to alter the terms of deal too much for Steve's taste.

Right, thanks for correcting my faulty memory on the timing.

It is possible that IBM tried to squeeze Apple, but given that IBM's interest in Transitive was for enterprise server migration, I suspect it is more likely that Apple got tired of paying whatever small royalty they'd contracted for with Transitive, and decided enough people had fully migrated to native x86 apps that they wouldn't alienate too many customers.

Re: Why is Rosetta 2 fast?

#326

Post by dougall »

tomcam wrote: post #172

> Every one-byte x86 push becomes a four byte ARM instruction Can someone explain this to me? I don’t know ARM but it just seems to me a push should not be that expensive.

Bit late, and the other comments are right, but it's worth noting that pushes typically aren't that expensive. ARM has a 4-byte STP (store paired) instruction that pushes two values at a time. So usually a push only costs two bytes on ARM, but if you're translating instruction-for-instruction it's four bytes.

(I also forgot while writing the post that 2-byte push instructions are common in 64-bit x86 as well. Half the registers can be pushed with a single byte, and the other half require a REX prefix, giving a two-byte push instruction. So even though the quoted statement is true, the difference isn't that bad in general.)

Re: Why is Rosetta 2 fast?

#327

Post by DonHopkins »

gumby wrote: post #236
masklinn wrote: post #94

Earlier quoted context omitted.

> 15? More than a quarter century. They were one of the original investors in ARM and have produced plenty of arm devices since then beyond the newton and the ipod. They didn't design their own chips for most of that time.

At the same time as the ARM investment they had a Cray for...chip design.

Back then, a Cray-1 could execute an infinite loop in 4.7 seconds.

Re: Why is Rosetta 2 fast?

#328

Post by solarkraft »

Gigachad wrote: post #238
johnthuss wrote: post #2

"I believe there’s significant room for performance improvement in Rosetta 2... However, this would come at the cost of significantly increased complexity... Engineering is about making the right tradeoffs, and I’d say Rosetta 2 has done exactly that."

Would be a waste of effort when the tool is designed to be obsolete in a few years as everything gets natively compiled.

They could've amazed a few people a bit more by emulating x86 apps even faster (but M1+Rosetta can already run some stuff faster than an Intel Mac), but then the benefit of releasing native apps would be much decreased ("why bother, it's good enough ...").

It's a delicate political game that they, yet again, seem to be playing pretty well.

Re: Why is Rosetta 2 fast?

#329

Post by solarkraft »

webwielder2 wrote: post #292

(Apologies for the flame war quality to this comment, I’m genuinely just expressing an observation) It’s ironic that Apple is often backhandedly complimented by hackers as having “good hardware” when their list of software accomplishments is amongst the most impressive in the industry and contrasts sharply with the best efforts of, say, Microsoft, purportedly a “software company.”

Both have pretty impressive engineering. The focus just appears to be different. Apple really cares about user experience (or, maybe, used to), while it seems like Microsoft is trying to (and according to what I hear mostly succeeding) nail the administration experience instead.

Re: Why is Rosetta 2 fast?

#330

Post by xattt »

savoytruffle wrote: post #206
GeekyBear wrote: post #192

Earlier quoted context omitted.

> It was originally a startup, but had been bought by IBM by the time Apple was interested. Rosetta shipped in 2005. IBM bought Transitive in 2008. The last version of OS X that supported Rosetta shipped in 2009. I always wondered if the issue was that IBM tried to alter the terms of deal too much for Steve's taste.

I agree it was a bit worryingly short-lived. However the first version of Mac OS X that shipped without Rosetta 1 support was 10.7 Lion in summer 2011 (and many people avoided it since it was problematic). So nearly-modern Mac OS X with Rosetta support was realistic for a while longer.

I could have have sworn that a unibody MacBook Pro where I did an in-place upgrade to Lion somehow held onto Rosetta.
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