[PATCH] D142348: [RISCV][Docs] Document code generation for vector extension

[Luke Lau via Phabricator via llvm-commits]

luke added inline comments.


================
Comment at: llvm/docs/RISCV/RISCVVectorExtension.rst:212
+One downside of this design is that it doesn’t allow vectors of i128 (this is, ELEN=128).
+In that case vscale would have to be 1/2 under :math:`\text{LMUL}=1`.
+This type (and its fp counterpart float128) are not that common and in case of extreme necessity types for :math:`\text{LMUL}=2` could be used instead.
----------------
LWenH wrote:
> Hi, as a doc reader I'm quite confuse why here for the i128 type would be the 1/2 under the LMUL=1. In order to represent the i128 type, shouldn't the vscale be extended to 2 (LMUL=1) to be more direct?
At LMUL=1, the minimum vector size should be 64 bits, but you can't specify the minimum vector length as anything less than 1 e.g. `<vscale x ½ x i128>`, if that makes sense. I guess it could represent i128 vectors at LMUL=2 with `<vscale x 1 x i128>` though


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142348/new/

https://reviews.llvm.org/D142348