[PATCH] D54686: [IR] Add hasNPredecessors, hasNPredecessorsOrMore to BasicBlock

[Vedant Kumar via Phabricator via llvm-commits]

vsk created this revision.
vsk added reviewers: davide, hfinkel, rnk.
Herald added subscribers: dexonsmith, rogfer01, george.burgess.iv, hiraditya.

Add methods to BasicBlock which make it easier to efficiently check
whether a block has N (or more) predecessors.

This can be more efficient than using pred_size(), which is a linear
time operation.

We might consider adding similar methods for successors. I haven't done
so in this patch because succ_size() is already O(1).

With this patch applied, I measured a 0.065% compile-time reduction in
user time for running `opt -O3` on the sqlite3 amalgamation (30 trials).
The change in mergeStoreIntoSuccessor alone saves 45 million linked list
iterations in a stage2 Release build of llc.

See llvm.org/PR39702 for a harder but more general way of achieving
similar results.


https://reviews.llvm.org/D54686

Files:
  llvm/include/llvm/ADT/STLExtras.h
  llvm/include/llvm/IR/BasicBlock.h
  llvm/include/llvm/IR/CFG.h
  llvm/lib/Analysis/MemorySSAUpdater.cpp
  llvm/lib/IR/BasicBlock.cpp
  llvm/lib/IR/Value.cpp
  llvm/lib/Transforms/IPO/PartialInlining.cpp
  llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
  llvm/lib/Transforms/Utils/Local.cpp
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/lib/Transforms/Vectorize/VPlan.cpp

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