sdesmalen added a comment. In D89031#2391248 <https://reviews.llvm.org/D89031#2391248>, @SjoerdMeijer wrote:
> In D89031#2391160 <https://reviews.llvm.org/D89031#2391160>, @david-arm wrote: > >> Hi @SjoerdMeijer I think that given we now support scalable vectors we >> thought it made sense to be able to specify whether the user wants 'fixed' >> or 'scalable' vectorisation along with the vector width, although without >> specifying the additional property the default continues to remain 'fixed'. >> However, what you said about having a vectorize_scalable pragma is correct >> and we are intending to also add a pragma like this in a future patch. > > Okay, I haven't looked at the implementation to be honest, but am just trying > to understand the different use cases of this first. > I just seem to be missing or not understanding why fixed/scalable is an > option to only vectorize_width, why not to vectorize(enable) or just a > separate one like vectorize_scalable? By making scalable/fixed and option to > vectorize_width, you can't toggle this for other pragmas like > interleave(enable) that enable vectorisation, which would be inconsistent? It > also seems to be more work to me to do this first for vectorize_width, and > then fix up other pragmas later. But I might be missing something (obivous) > here. Hi @SjoerdMeijer, all valid and good questions. We think it makes sense to allow specifying explicitly what the meaning of '4' is when specifying the width. So that `vectorize_width(4, fixed)` means vectorizing with `<4 x eltty>` and `vectorize_width(4, scalable)` means vectorizing with `<vscale x 4 x eltty>`. Like @david-arm said, we also plan to add something like `vectorize_style(fixed|scalable)`. This approach should be fully complementary to `vectorize_with` so that it would be possible to have: // Use scalable vectors, but leave it to the cost-model to choose the most efficient N in <vscale x N x eltty>. // If the pragma is not specified, it defaults to vectorize_style(fixed). #pragma clang loop vectorize_style(scalable) // Use <4 x eltty> #pragma clang loop vectorize_width(4, fixed) // Use <vscale x 4 x eltty> #pragma clang loop vectorize_width(4, scalable) // If vectorize_style(scalable) is specified, then use <vscale x 4 x eltty>, otherwise <4 x eltty> #pragma clang loop vectorize_width(4) // uses <4 x eltty> #pragma clang loop vectorize_width(4) vectorize_style(scalable) // uses <vscale x 4 x eltty> // Conflicting options, clang should print diagnostic and error or ignore the hint. #pragma clang loop vectorize_width(4, fixed) vectorize_style(scalable) I hope that gives a bit more context. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D89031/new/ https://reviews.llvm.org/D89031 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
