llvm-project

08a8e1c6 - [InstCombine] Move extends across identity shuffles. (#146901)

[InstCombine] Move extends across identity shuffles. (#146901) Add a new fold to instcombine to move SExt/ZExt across identity shuffles, applying the cast after the shuffle. This sinks extends and can enable more general additional folding of both shuffles (and related instructions) and extends. If backends prefer splitting up doing casts first, the extends can be hoisted again in VectorCombine for example. A larger example is included in the load_i32_zext_to_v4i32. The wider extend is easier to compute an accurate cost for and targets (like AArch64) can lower a single wider extend more efficiently than multiple separate extends. This is a generalization of a VectorCombine version (https://github.com/llvm/llvm-project/pull/141109) as suggested by @preames. PR: https://github.com/llvm/llvm-project/pull/146901