[LV] Don't scalarize loads that need predication in legacy CM.
The legacy cost model tries to scalarize loads that are used as
pointers. Skip if the load would need predicating when scalarized,
because that would incur very high costs, see useEmulatedMaskMemRefHack.
Fixes https://github.com/llvm/llvm-project/issues/180780.
llvm-project
d3afa171 - [LV] Don't scalarize loads that need predication in legacy CM.
