[PATCH] D97111: [RISCV] change rvv frame layout

[Roger Ferrer Ibanez via Phabricator via llvm-commits]

rogfer01 added a comment.

Hi @StephenFan. I wonder if we want to do this only when we index via `sp`.

My understanding is that the emergency slot will be close enough when we index via `fp`/`bp` in the previous layout. In the previous layout, when indexing a scalar via `sp` we have to cross the RVV part (which needs an extra register) to reach the scalar registers (where the emergency slot will be located). IIUC, your approach it fixes the `sp` case but complicates the `fp`/`bp` case to access the emergency slot we need to jump over RVV.

My suggestion means we want to have the RVV vectors as far from the frame pointer as possible (the one being used `sp`/`fp`/`bp`), so scalars are still straightforward to access even in the presence of RVV. This means different layouts when indexing with `sp` and  when indexing with `fp`/`bp`. In summary: your new layout for `sp` but the previous one for `fp`/`bp`. Does this make sense?


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https://reviews.llvm.org/D97111