Comment by cesarb
3 hours ago
> That's unfortunate, because it's precisely why things like this will keep happening.
I have the opposite opinion. Its use being rare means CPU designers have less need to optimize for that rare case, and hardware optimizations are precisely where these kinds of issues tend to pop up.
And high 8-bit registers are a x86-specific feature, other CPU families don't have it. So that special case being less optimized (or even pessimized) is not much of a loss.
Yep. The "high" registers as an alias for bits 8-15 of certain registers are one of many warts in the architecture; they should have been purged from 32-bit and 64-bit code, and left to rot in 16-bit mode only.
Intel blew it when they let them continue to work in to 32-bit code on the 386, and then AMD blew it when they repeated the mistake when defining the 64-bit ISA.