On Tue, Nov 7, 2023 at 8:33 PM Maxim Blinov via Gcc <gcc@gcc.gnu.org> wrote: > > I see, thanks for clarifying, that makes sense. > > In that case, what about doing the inverse? I mean, are there unique > patches in the vendor branch, and would it be useful to try to > upstream them into master? My motivation is to get the best > autovectorized code for RISC-V. > > I had a go at building the TSVC benchmark (in the llvm-test-suite[1] > repository) both with the master and vendor branch gcc, and noticed > that the vendor branch gcc generally beats master in generating more > vector instructions.
Note TSVC benchmark is part of GCC testsuite too: https://gcc.gnu.org/git/?p=gcc.git;a=tree;f=gcc/testsuite/gcc.dg/vect/tsvc/vect/tsvc;h=0a8f19a630bf39c28c6c6016bbc99a6421d83970;hb=HEAD Thanks, Andrew > > If I simply count the number of instances of each vector instruction, > the average across all 36 test cases of vendor vs master gcc features > the following most prominent differences: > > - vmv.x.s: 48 vs 0 (+ 48) > - vle32.v: 150 vs 50 (+ 100) > - vrgather.vv: 61 vs 0 (+ 61) > - vslidedown.vi: 61 vs 0 (+ 61) > - vse32.v: 472 vs 213 (+ 459) > - vmsgtu.vi: 30 vs 0 (+ 30) > - vadd.vi: 80 vs 30 (+ 50) > - vlm.v: 18 vs 0 (+ 18) > - vsm.v: 16 vs 0 (+ 16) > - vmv4r.v: 21 vs 7 (+ 14) > > (For reference, the benchmarks are all between 20k-30k in code size. > Built with `-march=rv64imafdcv -O3`.) > > Ofcourse that doesn't say anything about performance, but would it be > possible/fair to say that the vendor branch may still be better than > master for generating vectorized code for RISC-V? > > What's interesting is that there's very little "regression" - I saw > only very few cases where the vendor branch removed a vector > instruction as compared to master gcc (the most often removed > instruction by the vendor branch, as compared to master, is > vsetvl/vsetvli.) > > BR, > Maxim > > [1]: > https://github.com/llvm/llvm-test-suite/tree/main/MultiSource/Benchmarks/TSVC > > On Tue, 7 Nov 2023 at 15:53, Jeff Law <jeffreya...@gmail.com> wrote: > > > > > > > > On 11/7/23 05:50, Maxim Blinov wrote: > > > Hi all, > > > > > > I can see about 500 failing tests on the > > > vendors/riscv/gcc-13-with-riscv-opts, a mostly-full list at the bottom > > > of this email. It's mostly test cases scraping for vector > > > instructions. > > Correct. There are generic vectorizer changes that would need to be > > ported over to that branch to make those tests pass. I looked at this a > > few times and ultimately gave up in the rats nest of inter-dependent > > patches in the vectorizer. > > > > > > Given the lifetime of that branch is likely nearing its end, I don't > > think there's much value left in trying to port those changes over. Any > > such effort would likely be better spent nailing down issues on the trunk. > > > > jeff
