There's already multiple ISAs on SoCs, think GPUs, DSPs and the like. And the execution environment of each is different enough that they really have to be tre

There's already multiple ISAs on SoCs, think GPUs, DSPs and the like. And the execution environment of each is different enough that they really have to be treated as different architectures anyway, even if they are all "Based on RISC-V" or similar. Sharing parts of the toolchain and compiler backend may be of benefit to re-using similar architectures with tweaks for each application, but as someone who has worked on GPUs for a long time, generating working code is relatively easy. Generating performant code, however, is much harder, and the vast majority of the complexity in generating this performant code seems to have little in common with what makes serial CPU code fast, for example, so may be of less benefit than some people think.