Re:Don't use assembly unless you're an expert
by ithkuil on Friday April 04, 2014 @06:11AM
(#7530335)
yes, actually a better word would be code density. A weird encoding like x86 behaves like a compressed code, that gets decoded in the cpu into another instruction set that actually gets executed. This property, along with the backwards compatibility is what kept the x86 instruction set alive.
With the move to 64-bit, code had to be recompiled anyways; hence there was a good opportunity to reshape the x86 instruction set significantly. Instead, the number of changes were relatively small; the instruction set maintained his flavour (variable length encoding, a non orthogonal operands, ...). I believe there are many reasons for that choice (made by AMD), but code density was an key factor.
With the move to 64-bit, code had to be recompiled anyways; hence there was a good opportunity to reshape the x86 instruction set significantly. Instead, the number of changes were relatively small; the instruction set maintained his flavour (variable length encoding, a non orthogonal operands, ...). I believe there are many reasons for that choice (made by AMD), but code density was an key factor.