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Comment by awaythrow999 | Hacker News Reader

Frame pointers are still a no-go on 32bit so anything that is IoT today.

The reason we removed them was not a myth but comes from the pre-64 bit days. Not that long ago actually.

Even today if you want to repurpose older 64 bit systems with a new life then this of optimization still makes sense.

Ideally it should be the default also for security critical systems because not everything needs to be optimized for "observability"

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> Frame pointers are still a no-go on 32bit so anything that is IoT today.

Isn't that just 32-bit x86, which isn't used in IoT? The other 32-bit ISAs aren't register-starved like x86.

It would be, yes. x86 had very few registers, so anything you could do to free them up was vital. Arm 32bit has 32 general purpose registers I think, and RISC V certainly does. In fact there's no difference between 32 and 64 bit in that respect. If anything, 64-bit frame pointers make it marginally worse.

Sadly, no. 32-bit ARM only has 16 GPR’s (two of which are zero and link), mostly because of the stupid predication bits in the instruction encoding.

That said, I don’t know how valuable getting rid of FP on ARM is - I once benchmarked ffmpeg on 32-bit x86 before and after enabling FP and PIC (basically removing 2 GPRs) and the difference was huge (>10%) but that’s an extreme example.

Arm32 doesn’t have a zero-value register. Its non-general-purpose registers are PC, LR, SP, FP – tho the link register can be used for temporary values.

Ah yes - the weird one was PC not zero. Anyhoo, all of these mistakes were fixed with Arm64.

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