x86 prefixes and escape opcodes flowchart
1–10 of 53 posts
Re: x86 prefixes and escape opcodes flowchart
#2This site redirects to HN when it notices HN in the referrer.
Re: x86 prefixes and escape opcodes flowchart
#3Re: x86 prefixes and escape opcodes flowchart
#4This site redirects to HN when it notices HN in the referrer.
open in new tab
Re: x86 prefixes and escape opcodes flowchart
#5I respect the disobedience.
Re: x86 prefixes and escape opcodes flowchart
#6This is in no small part why x86 code density is awful despite variable size encoding.
Re: x86 prefixes and escape opcodes flowchart
#7This site redirects to HN when it notices HN in the referrer.
Wow, I didn't even notice because I have extensions that strip the referrer header. Excellent.
Re: x86 prefixes and escape opcodes flowchart
#8This site redirects to HN when it notices HN in the referrer.
If you have JavaScript enabled, that is. JWZ at least does the redirect on the server side.
The following is pulled in from `https://soc.me/assets/js/turnBack.js`:
const undesirables = [
"news.ycombinator.com/",
// "reddit.com/", // disable temporaily
"lobste.rs/"
] ;
if (undesirables.find(site => document.referrer.includes(site))) {
window.location.replace(document.referrer);
}
Re: x86 prefixes and escape opcodes flowchart
#9This is in no small part why x86 code density is awful despite variable size encoding.
Awful compared to what?
I've seen benchmarks that go both ways in terms of a "winner" but in terms of overall variance there seems to be very little. There are some cases where ARM64 or RISCV do better and there are some cases where x86_64 does better. I can't see code density being a relevant factor when picking one ISA over another.
We've got good compilers now anyways.. outside of power consumption.. the ISA wars are dead.
Re: x86 prefixes and escape opcodes flowchart
#10Fun little tidbit: The 0x40-0x4f range used for the REX prefix actually clashes with the single-byte encodings for increment/decrement.
When AMD designed the 64 bit extension, they had run out of available single-byte opcodes to use as a prefix and decided to re-use those. The INC/DEC instructions are still available in 64 bit mode, but not in their single-byte encodings.