lenary added a comment. In D119720#3339855 <https://reviews.llvm.org/D119720#3339855>, @dmgreen wrote:
> I have a high level question regarding RDF, as I've not seen it used in many > other places, so it may be under-tested on Arm systems at the moment. This > currently, for all code, builds an rdf graph, analyze the rdf graph for a > fairly rare instructions, then fixes up the code based on that. It might be > best to avoid the (possibly expensive?) rdf graph generation for the common > case where the instructions are not present. Check that the instruction > exists first. I haven't had time to see what effect this has on compile times, but I don't see the point in iterating over every instruction in the function checking the opcode, to then iterate over them all constructing the rdfgraph, that seems to make the approach a lot more expensive, if I'm then going to iterate over the rdfgraph looking for specific instructions again. > It might then be simpler to just search back for the def of a register, > considering in most code the instruction we are looking for should be fairly > rare and we won't expect to need to find def's in bulk. That might be simpler > overall, and avoid some of the difficulties of RDF. The reason for using the rdfgraph was to allow us to improve this at a later date if we found the performance issues a problem, i.e. by hoisting the `vorr` past phis so we can save on executing them in loops. Given the issues with rdfgraph, I'm going to reimplement this as a Block-local analysis and fixup pass without the rdfgraph, which is effectively what the pass does in the current patch. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D119720/new/ https://reviews.llvm.org/D119720 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
