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I keep coming back to this table and wondering why the conclusion was that 16-bit instructions were necessary and not more complex 32-bit instructions were nece
by sweetjuly 3y ago
I keep coming back to this table and wondering why the conclusion was that 16-bit instructions were necessary and not more complex 32-bit instructions were necessary. For example, ARMv8's LDR and LDP instructions are amazing and turn what is often 3-4+ 32-bit RISC-V instructions into just one 32-bit instruction. Making C optional and building a new "code size reduction" extension that is more suitable for large application processors (which can reasonably be assumed to use uops) would help so much more.
- snvzz 3y ago> Making C optional and building a new "code size reduction" extension that is more suitable for large application processors (which can reasonably be assumed to use uops) would help so much more. Andrew at SiFive disagrees vehemently[0]. 0. https://lists.riscv.org/g/tech-profiles/message/391 https://lists.riscv.org/g/tech-profiles/message/391
- sweetjuly 3y agoAndrew seems to mostly disagree with Qualcomm in general and is rejecting the idea not so much out of technical merit but because he doesn't believe them. Qualcomm is definitely not alone with its dislike of the C extension and trying to wholesale dismiss criticisms of it because they're coming from Qualcomm is not appropriate.
- snvzz 3y agoSiFive made a technical case[0] on keeping C, too. >Qualcomm is definitely not alone It's also worth noting that they tried to appropriate Rivos's opinion, only to be called out[1]. 0. https://lists.riscv.org/g/tech-profiles/topic/slides_on_retaining_ialign_16/101922590 https://lists.riscv.org/g/tech-profiles/topic/slides_on_reta... 1. https://lists.riscv.org/g/tech-profiles/message/396 https://lists.riscv.org/g/tech-profiles/message/396