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By "these days" you mean "since AMD messed it up".
by userbinator 1y ago
By "these days" you mean "since AMD messed it up".
- peterfirefly 1y agoObviously not. Even if you dislike the REX prefixes of AMD64, you've got to think about the 66/F2/F3 prefixes used for older SIMD instructions. They were introduced by Intel and basically contribute to more opcode bits. There's also the 2E/3E prefixes used for static branch prediction hints in some Pentium 4's (and also in new/upcoming Intel CPUs). VEX is from Intel, EVEX is from Intel, and the upcoming REX2 is also from Intel.
- userbinator 1y agoREX is horrible because they occupy two full rows of what were otherwise very useful instructions (inc/dec), and there were other gaps and less-useful instructions (segment override prefixes? If segmentation doesn't work in AMD64 mode, what's the point?) in the opcode map they could've used instead.