[PATCH] D131508: [WIP][RISCV] Enable fixed length vectorization

Sergei Barannikov via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Aug 9 16:07:58 PDT 2022


barannikov88 added a comment.

In D131508#3711061 <https://reviews.llvm.org/D131508#3711061>, @reames wrote:

> @barannikov88 - I don't see how your last comment connects to this review.  If you want to ask a question on your hardware, please email me and we can chat briefly.

Sorry for intervening. I wanted to bring to your attention that if you map fixed vectors to scalable registers, you will need a way to know the effective size of the register when a need for a spill arises.
I don't know if the ISA allows you to extract the number of elements from the internal part of the vector register, but you can always spill 128 bits (the min VLEN), wasting some stack space if the effective size is smaller.
That is just of more importance for our target, so I was wondering how are you going to solve this spilling issue, if at all.


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