llvm-project

8e2f6495 - [DAGCombiner] Do not always fold FREEZE over BUILD_VECTOR (#85932)

[DAGCombiner] Do not always fold FREEZE over BUILD_VECTOR (#85932) Avoid turning a BUILD_VECTOR that can be recognized as "all zeros", "all ones" or "constant" into something that depends on freeze(undef), as that would destroy those properties. Instead we replace undef by 0/-1 in such vectors, making it possible to fold away the freeze. We typically use -1 if the BUILD_VECTOR would identify as "all ones", and otherwise we use the value 0.