>Register re-naming was invented to ensure that we enjoy the benefits of improvements in hardware without having to recompile. Let us assume you have a processo

>Register re-naming was invented to ensure that we enjoy the benefits of improvements in hardware without having to recompile. Let us assume you have a processor with 16 registers. You compiled software for it. Now we can put in 32. What do you do? Recompile everything out there or implement register re-naming? Just run the software? Nothing forces a software to use all available registers, if yours was compiled for 16 and the CPU has 32, it uses 16 registers. Modern CPUs have plenty of additional instruction codes too and you don't need to recompile your software because one CPU has the RDRAND instruction and some other doesn't have it (minus AMD breaking RDRAND but that's a different topic). >The micro-ops and the hardware itself, is RISC. I would argue that µOps are VLIW wearing a RISC hat, it's very VLIW-y what's happening under the hood in x86, just less coherent. >On top of it, if you had a 4-wide VLIW and then you wanted to make a 8-wide one, you had to recompile. And oh, the "rotating registers" in VLIW is a form of register re-naming. As mentioned above, in that case the software doesn't perform as well as it could but there is no reason it would stop working if you properly designed it.