[LSR/LFTR] Move two utilities to common code for reuse [nfc]

We're working on a transform in LSR which is essentiall an inverse of LFTR (in certain sub-cases).  Move utilties so that they can be reused.

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 7df8651..1c58370 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -466,6 +466,19 @@ llvm::collectChildrenInLoop(DomTreeNode *N, const Loop *CurLoop) {
   return Worklist;
 }
 
+bool llvm::isAlmostDeadIV(PHINode *PN, BasicBlock *LatchBlock, Value *Cond) {
+  int LatchIdx = PN->getBasicBlockIndex(LatchBlock);
+  Value *IncV = PN->getIncomingValue(LatchIdx);
+
+  for (User *U : PN->users())
+    if (U != Cond && U != IncV) return false;
+
+  for (User *U : IncV->users())
+    if (U != Cond && U != PN) return false;
+  return true;
+}
+
+
 void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT, ScalarEvolution *SE,
                           LoopInfo *LI, MemorySSA *MSSA) {
   assert((!DT || L->isLCSSAForm(*DT)) && "Expected LCSSA!");