Team sync‐ups

22-mar-25 (Exegesis):

• Article about RVV: https://fprox.substack.com/p/risc-v-vector-extension-in-a-nutshell-part-1
• Patch from SiFive:
  • Problem is: same instructions produce different results based on vsetvl
  • Current solution is:
    • Generate all possible vector unit programming cases in snippets for benchmarking using multiple passes:
      • RISCVInsertVSETVIPass
      • RISCVInsertWriteVXRMPass
      • Post-processing pass
    • Patch introduced opcodes in MCInstr

16-mar-25 (Exegesis):

• Three patches for RVV for Exegesis:
  • Initial support (merged): https://github.com/llvm/llvm-project/pull/128767
  • Improvements (opened, no activity): https://github.com/llvm/llvm-project/pull/114149
  • Winter school (not finished): https://github.com/e1turin/llvm-project/pull/1
• We need to understand what was already done: so a to-do is to check which instructions are currently supported
• A good path would be to track what's going on in current implementation for some know-to-work instruction (like vmul)
• CI will wait (a month approximately)

16-mar-25 (MCA):

• Read: https://habr.com/ru/articles/474460/
• grep how MCA uses SchedModel (I guess we should not change any interfaces)
• scalable vectorization in other CPUs in LLVM: What's number of microops?
• take a look at MCA for SiFive CPUs
• Need to add FU count in a sched model
• RISCVSchedSiFiveP400.td for reference
  • Try to feed to MCA, how it handles RVV

12-mar-25 (Syntacore):

• More interactions with green team
• performance tools (llvm-based):
  • llvm-mca: code analysis (any random code snippet)
  • llvm-exegesis: hardware analysis
• We need to try to union them in some sort
• Exegesis doesn't use LLVM's SchedModel as full as possible. Initial RVV is supported
• Traditional LLVM's SchedModel doesn't suite RVV well: we need to widen it (e.g. functional units number)
• MCA RVV: no rvv at all
• Decomp: mca rvv , schedmodel for exegesis , widening schedmodel for RVV, bring-up (saturn-vectors, real hardware)
• Need to do decomposition
• Org
  • Biweekly meetings
  • Monthly -- both teams
  • Next meeting: 19-mar-25
• Need to get familiar with both tools