I am not particularly qualified to try and design a better ISA, I just know there are some things I would like the option to control at some times (or at least I imagine I would). A lot of the list above is about exposing more of the architecture to user control as a general principle. However, I’d rather see some areas of hardware design change to facilitate something other than coding paradigms and practices that stretch back nearly 40 years. Chisnall’s ‘C is not a Low Level Language’ article discusses several architectural directions I would like to see happen, but also talks about how as long as the ISA remains the same moving to new programming styles/philosophies continues to be a difficult proposition.
The world has mostly not adopted existing tools for writing 10-100x faster software (simd, huge pages, computing both branches then using a blend or cmov when this is sufficiently cheap, software prefetching, collection APIs that support bulk updates so that they can use all of these things instead of adding totally unnecessary dependency chains to the resulting program, etc.) so i'm not optimistic about things getting better if CPUs grow a thousand times more memory bandwidth and cores and begin to support very wide scatter/gather like GPUs.
Other than that they are very similar
I really would get onboard with an alternative ISA that was more in line with actual architectural features of modern processors and I often wonder why we could not have an extra compilation (jit or aot) step from x86 to some other format. But the trend seems to be going the opposite direction for all the large scale processor manufacturer/designers toward a more abstracted interface at the lowest level.
I’ve seen various comments that basically boil down to “you can’t change the ISA because then C/C++/Rust programs would loose performance in benchmarks in the short term”, and this resistance only reinforces maintaining current trends. So… what are you assuming happens that prompts the shift toward a better way to harness computing power?