efriedma added inline comments.
================ Comment at: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:7670 + Mask, Op.getOperand(0), Op.getOperand(1)); +} + ---------------- sdesmalen wrote: > efriedma wrote: > > If we're going to support these operations, we might as well just add isel > > patterns; that's what we've been doing for other arithmetic operations. > Just to provide a bit of context to this approach: > > For unpredicated ISD nodes for which there is no predicated instruction, the > predicate needs to be generated. For scalable vectors this will be a `ptrue > all`, but for fixed-width vectors may take some other predicate such as VL8 > for fixed `8` elements. > > Rather than creating new predicated AArch64 ISD nodes for each operation such > as `AArch64ISD::UDIV_PRED`, the idea is to reuse the intrinsic layer we > already added to support the ACLE - which are predicated and for which we > already have the patterns - and map directly onto those. > > By doing the expansion in ISelLowering, the patterns stay simple and we can > generalise `getPtrue` method so that it generates the right predicate for any > scalable/fixed vector size as done in D71760 avoiding the need to write > multiple patterns for different vector lengths. > > This patch was meant as the proof of concept of that idea (as discussed in > the sync-up call of Apr 2). Using INTRINSIC_WO_CHAIN is a little annoying; it's hard to read in DAG dumps, and it gives weird error messages if we fail in selection. But there aren't really any other immediate downsides I can think of, vs. doing it the other way (converting the intrinsic to AArch64ISD::UDIV_PRED). Long-term, we're going to have a target-independent ISD::UDIV_PRED. We probably want to start using those nodes at some point, to get target-independent optimizations. Not sure if that impacts what we want to do right now. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D78569/new/ https://reviews.llvm.org/D78569 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
