In foldSelectIntoOp we sometimes transform a select of a fadd into a fadd of a select, where we select between data and an identity value. For both fadd and fsub the identity is always -0.0, but if the nsz flag is set on the select instruction we can use +0.0 instead. Doing so then triggers other optimisations, such as when folding the select of masked load into a new masked load. Differential Revision: https://reviews.llvm.org/D126774