llvm-project

82ef7e54 - [X86] combineVTRUNCSAT - attempt to recognise VTRUNCS/US(CONCAT(X,Y)) -> PACKSS/US(X,Y) folds. (#178707)

[X86] combineVTRUNCSAT - attempt to recognise VTRUNCS/US(CONCAT(X,Y)) -> PACKSS/US(X,Y) folds. (#178707) If we're just concatenating subvectors together to perform a saturated truncate, see if we can perform PACK on the subvectors directly instead - 256-bit PACK will require a post-shuffle, but this will typically fold away in later shuffle combining and its probably better than changing vector widths with concats. Reference patch based off poor codegen identified in #169995