4 ms·

There are already profiles for ISA configuration. But that is a feature not a bug.

by nickik 6y ago

pjmlp 6y ago
When that C code cannot run because of proprietary extensions, I guess it is a feature for the compiler vendor using an in-house fork of clang.
- finnthehuman 6y ago
  That's already the status quo for many specialty processors. Either they're doing something unique enough in hardware that you pay for the development seats and special interfacing hardware, or you go with a generic part and get to use all the cheap/opensource tools.
- nickik 6y ago
  What is the alternative. If your goal is for RISC-V to be universal you have to support lots of things. RISC-V strategy make sense, first standise the core that allows you to run all tooling. At necessary thigns like floats and so on. And the move on into more interesting extentions like Vectors. If a company does something unique, the can take the standard compiler and have standard way to add an extra extention. Of courese because the world is not perfect you will have some sudo standards and companies that have their own version of some of these. Profiles is a way to manage that and to find configuration of extentions that often work together for desktop, embeeded or something like that. Seem relativivly well thought out for something that has such braod application.
  - sifar 6y ago
    >> Profiles is a way to manage that and to find configuration of extentions that often work together for desktop, embeeded or something like that In theory yes, what happens in practice is for your application, you only need a few operations from N different extensions and now you have to implement all those extensions, if you want to be compatible. The alternative is you develop the few ops as custom isa and break compatibility. So you can either be non compatible and lean or compatible and bloated. Guess what will processor/chip designers will prefer given the energy constraints.
    - nickik 6y ago
      If you have such a costume chip that you optimize on an instruction by instruction level software comparability probably doesn't matter that much. > So you can either be non compatible and lean or compatible and bloated. That's a waste overstatement. The profiles are optimized for specific fields already and you have to evaluate if you want to take advantage of all the software and infrastructure around that profile of if you want to redo all the work just so you can cut out a few specific instruction. You act like as if every company makes its own costume chips with the minimal set of instructions they need, but that is about 0.01% of the market or less. For the waste majority of use case simply not required and standard embedded profile is perfectly reasonable. And the commercial chips and commercial software will also target that profile. If you really want to redo everything with your costume chips and compilers, software and so on then that's your choice and RISC-V should not prevent that.
sifar 6y ago
It is a bug not a feature. It leads to hardware bloat which will lead to people developing custom instructions which leads to incompatibility and now you don't have a generic universal isa that you wanted.

There are already profiles for ISA configuration. But that is a feature not a bug.

by nickik 6y ago

There are already profiles for ISA configuration. But that is a feature not a bug.

When that C code cannot run because of proprietary extensions, I guess it is a feature for the compiler vendor using an in-house fork of clang.

finnthehuman 6y ago
That's already the status quo for many specialty processors. Either they're doing something unique enough in hardware that you pay for the development seats and special interfacing hardware, or you go with a generic part and get to use all the cheap/opensource tools.
nickik 6y ago
What is the alternative. If your goal is for RISC-V to be universal you have to support lots of things. RISC-V strategy make sense, first standise the core that allows you to run all tooling. At necessary thigns like floats and so on. And the move on into more interesting extentions like Vectors. If a company does something unique, the can take the standard compiler and have standard way to add an extra extention. Of courese because the world is not perfect you will have some sudo standards and companies that have their own version of some of these. Profiles is a way to manage that and to find configuration of extentions that often work together for desktop, embeeded or something like that. Seem relativivly well thought out for something that has such braod application.
- sifar 6y ago
  >> Profiles is a way to manage that and to find configuration of extentions that often work together for desktop, embeeded or something like that In theory yes, what happens in practice is for your application, you only need a few operations from N different extensions and now you have to implement all those extensions, if you want to be compatible. The alternative is you develop the few ops as custom isa and break compatibility. So you can either be non compatible and lean or compatible and bloated. Guess what will processor/chip designers will prefer given the energy constraints.
  - nickik 6y ago
    If you have such a costume chip that you optimize on an instruction by instruction level software comparability probably doesn't matter that much. > So you can either be non compatible and lean or compatible and bloated. That's a waste overstatement. The profiles are optimized for specific fields already and you have to evaluate if you want to take advantage of all the software and infrastructure around that profile of if you want to redo all the work just so you can cut out a few specific instruction. You act like as if every company makes its own costume chips with the minimal set of instructions they need, but that is about 0.01% of the market or less. For the waste majority of use case simply not required and standard embedded profile is perfectly reasonable. And the commercial chips and commercial software will also target that profile. If you really want to redo everything with your costume chips and compilers, software and so on then that's your choice and RISC-V should not prevent that.

sifar 6y ago

It is a bug not a feature. It leads to hardware bloat which will lead to people developing custom instructions which leads to incompatibility and now you don't have a generic universal isa that you wanted.