On Tue, Jan 23, 2024 at 01:03:46PM +0100, Richard Biener wrote: > On Tue, 23 Jan 2024, Jakub Jelinek wrote: > > > On Tue, Jan 23, 2024 at 12:56:52PM +0100, Richard Biener wrote: > > > The following avoids using exact_log2 on the number of SIMD clone calls > > > to be emitted when vectorizing calls since that can easily be not > > > a power of two in which case it will return -1. For different simd > > > clones the number of calls will differ by a multiply with a power of two > > > only so using floor_log2 is good enough here. > > > > > > Bootstrap and regtest running on x86_64-unknown-linux-gnu. > > > > > > PR tree-optimization/113552 > > > * tree-vect-stmts.cc (vectorizable_simd_clone_call): Use > > > floor_log2 instead of exact_log2 on the number of calls. > > > > Is there any target which supports non-power-of-two simdlen? > > If not, perhaps we should add !pow2p_hwi (num_calls) to the continue; > > condition a few lines earlier? > > Is non-power-of-two simdlen a thing? Note there's nothing wrong > with non-power-of-two num_calls, with VF == 4 and a group size > of 3 you get 12 lanes and either 3 (simdlen == 4) or 6 (simdlen == 2) > calls. > > Iff non-power-of-two simdlen is a thing then we could bias > by + num_calls (no idea why we use *_log2 in the first place, but it > was that way since the beginning).
Ah, with SLP I can understand it doesn't have to be a power of two, the original + if (n->simdclone->simdlen + < (unsigned) LOOP_VINFO_VECT_FACTOR (loop_vinfo)) + this_badness += (exact_log2 (LOOP_VINFO_VECT_FACTOR (loop_vinfo)) + - exact_log2 (n->simdclone->simdlen)) * 1024; was written for loop vectorization only and I think correctly assumed power of 2 loop vectorization factors as well as simdlens. I admit I don't remember why log2 rather than the count has been used, the first version of the patch is https://gcc.gnu.org/pipermail/gcc-patches/2013-November/374728.html But if we keep using log2, perhaps better ceil_log2 because num_calls of 3 is certainly more expensive than 2. Jakub
