Lowering/isel of load with offset

[Sam Parker-Haynes]

Hi,

I'm trying to introduce a new load-type node and I've been looking at LaneMemory as an example. When LoadLane is selected, in the arm64 backend, there appears to be an assumption that the offset is always zero. In my example, that is not the case. So, I was wondering how this guarantee is made for Simd128LaneMemoryOps? And also, would it be possible to move the offset into a register during isel?

Cheers,

Sam

[dmerc...@google.com]

Hi,

From a quick look, it seems Simd128LaneMemoryOps are only created in wasm/turboshaft-graph-interface.cc, and there, the offset is always 0. Then, there is no phases at all that reduces (or even looks at for that matter) Simd128LaneMemoryOp, so when we reach the ISEL, the offset should still be 0.

> And also, would it be possible to move the offset into a register during isel?

I would guess that yes, but I haven't looked at the details. Alternatively, some normalization could be done right before the ISEL in load-store-simplification-reducer.h.

Cheers,

Darius

[Sam Parker-Haynes]

Okay, thanks, then I will just use WordPtrAdd at the graph level too.