[DAGCombiner] loosen constraints for fsub+fadd fold

isNegatibleForFree() should not matter here (as the test diffs show)
because it's always a win to replace an fsub+fadd with fneg. The
problem in D50195 persists because either (1) we are doing these
folds in the wrong order or (2) we're missing another fold for fadd.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339299 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed