alt Hacker NewsCPU architectures evolve and often get replaces, eg Mac has moved from 68k -> Power -> x86 -> ARM or even Windows PC have also jumped from 32 to 64 bits and the same is also true of SIMD.
Why dont O/S support executables with something like LLVM binaries and generate the native code at load time ?
This would solve so many problems including the need for emulators, because all binaries would work on all CPUS, and the OS would produce the best code at load time.
No more cpu detection, vector stuff always works on the latest & widest instructions that are available. CPUs can also retired old legacy instructions without worry and more.
Replies
postalrat • today at 4:41 AM
Would that support self modifying code?
This does exist, we call it Java (or C# or probably a dozen other implementations)
The big tradeoff you're making is that you have significantly less time to run your optimizer, since not everybody has a beefy machine or the patience to wait a day for their browser to start first time.
You could try doing optimization ahead of time, but I think (I could be wrong here) you would inevitably end up adding in some CPU assumptions if you went much further. This also somewhat conflicts with an advantage of VM based execution, that new optimizations apply to old binaries.
I'll also note that hand rolled assembly/SIMD code still beats compilers at the extreme end and you would either have to throw that away, or get all the disadvantages mentioned above without all the advantages