Hi, I need to learn much more about ARM architecture, but I have some initial comments.
Julian Brown <jul...@codesourcery.com> wrote on 15/09/2010 11:37:21 AM: > * automatic vector size selection (it's currently selected by command > line switch) > Generally (check assumption) I think that wider vectors may make inner loops more efficient, > but may increase the size of setup/teardown code (e.g. setup: increased versioning. Teardown, > increased insns for reduction ops). More importantly, sometimes larger vectors may inhibit vectorization. > We ideally want to calculate costs per vector-size per-loop (or per other vectorization opportunity). There is a patch http://gcc.gnu.org/ml/gcc-patches/2010-03/msg00167.html that was not committed to mainline (and I think not to vect256, but I am not sure about that). This patch tries to vectorize for the wider option unless it is impossible because of data dependence constraints. I agree with that cost model approach. > > * ensure that all gcc vectorizer pattern names are implemented in the > machine description (those that can be). In my opinion we better concentrate on: > * Conversly, perhaps identify NEON capabilities not covered by GCC > patterns, and add them to gcc (e.g. vld2/vld3/vld4 insns) Most of the existing vectorizer patterns were inspired by Altivec's capabilities. I think our approach should originate from the architecture and not the other way around. For example, I don't think we should spend time on implementation of vect_extract_even/odd and vect_interleave_high/low (even though they seem to match VUNZIP and VZIP), when we have those amazing VLD2/3/4 and VST2/3/4 instructions. > > I've not even started on looking at: > > * loops with more than two basic blocks (caused by if statements > (anything else?)) What do you mean by that? If-conversion improvements? > > Do you (Ira) have access to the ARM ISA docs detailing the NEON > instructions? I have "ARM® Architecture Reference Manual ARM®v7-A and ARM®v7-R edition". Ira > > Cheers, > > Julian[attachment "CS308-vectorization-improvements.txt" deleted by > Ira Rosen/Haifa/IBM] _______________________________________________ linaro-toolchain mailing list linaro-toolchain@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-toolchain
