SSE1 only supports v4f32. But does have instructions like movlps/movhps that load/store 64-bits of memory.
This patch breaks the connection between the node VT of the vzext_load/vextract_store patterns and the memory VT. Enabling a v4f32 node with a 64-bit memory VT. I've used i64 as the memory VT here. I've written the PatFrag predicate to just check the store size not the specific VT. I think the VT will only matter for CSE purposes. We could use v2f32, but if we want to start using these operations in more places a simple integer type might make the most sense.
I'd like to maybe use this same thing for SSE2 and later as well, but that will need more work to be supported by EltsFromConsecutiveLoads to avoid regressing lit tests. I'd maybe also like to combine bitcasts with these load/stores nodes now that the types are disconnected. And I'd also like to consider canonicalizing (scalar_to_vector + load) to vzext_load.
If you want I can split the mechanical tablegen stuff where I added the 32/64 off from the sse1 change.