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6:18:42
hayley
Well, I sent an email to Cliff Click asking about what he thought about callee saved registers, and I expected to not get a response any time soon. I was amazingly proved wrong.
6:23:27
hayley
The context was the "Bits of advice for VM writers" presentation, where he is also critical of callee-saves registers on x86 <https://www.youtube.com/watch?v=vzzABBxo44g>. I asked if he thought inlining (or call site optimization) changes the assumptions made, and if he thinks callee-saves is a good idea on x86-64 or ARM.
6:24:49
hayley
He said callee-saves was very messy in concurrent stack scanning on HotSpot, and "it wasn't really worth it for all the very-low-frequency GC bugs that entailed." And that callee-saves can sometimes get a small win on x86-64, because spilling is optimized. But on a RISC there is a larger win.
6:25:36
hayley
But, as he said it was "since leaf routines make up (nearly by definition) 50% of all calls", I wonder if I didn't communicate that I was interested in how these change under inlining.
6:36:00
hayley
I have sent a reply asking if he would change his mind with inlining, as our (some of the SICL developers) hypothesis is that there would be fewer but larger leaf functions under inlining or call site optimization.
7:30:56
moon-child
I wonder if https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/cheri-faq.html would be useful for implementing barriers
7:31:31
moon-child
though I'm not sure the extent to which it's available on production hardware; it has apparently been ported to riscv
7:56:04
beach
I wonder where all these people get all these resources. It looks like a huge amount of work.
7:57:10
moon-child
it would be an understatement to say that java was _very_ commercially successful
8:01:14
beach
With respect to callee-saves registers, I am not convinced that they are not worth the trouble for a dynamically typed language with automatic memory management.
8:03:53
shka
https://www.eetimes.com/arm-to-deliver-cheri-based-prototype-to-tackle-security-threats/#
8:04:28
shka
military and intelligence community in the USA is very concerned about the security of the computer systems
8:08:33
beach
It is "amusing" to me that all these resources are spent on trying to make intrinsically unsafe language somewhat safe, rather than on using good languages instead.
8:17:06
shka
and getting even few percent of saved memory/cpu time on the scale of azure would lead to millions of dollars in savings
8:17:50
shka
plus there are those intel security bugs, if you could somehow run old microcode version safely, again a lot of money saved