[DAG, X86] Improve Dependency analysis when doing multi-node
Instruction Selection
Cleanup cycle/validity checks in ISel (IsLegalToFold,
HandleMergeInputChains) and X86 (isFusableLoadOpStore). Now do a full
search for cycles / dependencies pruning the search when topological
property of NodeId allows.
As part of this propogate the NodeId-based cutoffs to narrow
hasPreprocessorHelper searches.
Reviewers: craig.topper, bogner
Subscribers: llvm-commits, hiraditya
Differential Revision: https://reviews.llvm.org/D41293
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@324359
91177308-0d34-0410-b5e6-
96231b3b80d8