On Binary Translation and Its Consequences

(chipsandcheese.com)

25 points by matt_d2 days ago

2 comments

cwzwarich1 hour ago
[Disclaimer: I wrote Rosetta 2, so everything I say is biased by that.]Contemporary out-of-order CPUs are incredibly over-provisioned; microarchitects will justify a new feature by another 0.1% gain on some benchmark. The end result is a CPU that's pretty decent at handling the sort of code bloat that comes from a binary translator.There's also a big tradeoff in adding more optimizations to a binary translator. You would like to be able to precisely handle exceptions (especially ones caused by invalid memory accesses) while presenting a userspace exception handler with an architecturally valid state for the source program. There are some optimizations that would be easy to do in principle but are painful for maintaining this mapping between source program states and translated program states. The complexity burden combined with the difficulty of debugging that added complexity (or exhaustively verifying it up-front) shapes many of your decisions when writing a production binary translator. You should always have more Cool (tm) ideas than you actually use in practice.
- 349ru3h4f0330 minutes ago
 Would Rosetta 2 have worked as well for x86 APX i.e. 32 GPRs instead of 16?(16x x86 regs fit in 32x Arm regs, whereas 32x in 32x is... much less of a fit)
functionmouse2 hours ago
> Consumers in the PC segment expect high performance across a wide range of applicationsIt seems there is a persistent rift between what hardware designers think users want and what users are asking for, only recently being addressed by major OEMs with products such as the MacBook Neo.Nobody I personally know wants a faster CPU; they want competent, faster, native feeling software and more power efficient hardware. CPUs have been plenty fast for at least a decade now, for anything the majority of users and even gamers are doing. I'm playing through the new and notoriously demanding LEGO Batman game on an RTX 2080 and an i7-4790k, a CPU from 2013 that even the base M1 easily beats. The game runs fine. Most people I am confident do not need better than the M1.
- hedgehog9 minutes ago
 I think you underestimate how intensive it is to scroll LinkedIn in Edge while a YouTube video, Outlook, Adobe's updaters, antivirus, device management, and whatever incidental malware the user has picked up run in the background. That's the reality for a lot of people.
- yjftsjthsd-h1 hour ago
 I was under the impression that race-to-idle made "fast" a significant factor in "power efficient"? Obviously needs software to not be terrible and needs to be able to scale the back down, but still.
 - cwzwarich1 hour ago
 That may be true at iso-voltage/frequency, but there are definitely places on that curve where it is better to be at a lower voltage (and thus frequency) than to run at a higher voltage just so you can race to idle.
- pjmlp1 hour ago
 MacBook Neo certainly does not address my needs with a 8 GB and 512 SSD for 900 euros.Additionally people shipping Electron crap also don't address my needs at all, everything that is Web based I already have an installed browser for it.
- aleph_minus_one2 hours ago
 > It seems there is a persistent rift between what hardware designers think users want and what users are asking for> Nobody I personally know wants a faster CPU; they want competent, faster, native feeling software and more power efficient hardware.I think you miss the point: what you claim that users want is not something that hardware designers have a lot of influence on (except for the aspect that the IC should be (more) power-efficient): these are rather problems that software developers are there to solve. So, hardware designers are simply the wrong persons to ask if you have such wishes.
 - layer81 hour ago
 That’s right, but power efficiency is an important factor, one of the main points where Intel is lagging behind ARM. And it’s also correct to point out that the main issue for end users is software, even if hardware designers can’t do much about it.