[llvm] [ConstraintElim] Add lower bounds for all inductions in a loop header. (PR #216764)

[Yingwei Zheng via llvm-commits]

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@@ -965,6 +974,84 @@ static void dumpConstraint(ArrayRef<int64_t> C,
 }
 #endif
 
+/// Splits the induction phi \p PN into the start value, coming from the loop
+/// predecessor \p LoopPred, and the step value, coming from inside the loop.
+/// Returns {nullptr, nullptr} if \p PN has other incoming values.
+static std::pair<Value *, Value *> getStartAndStep(const PHINode &PN,
+                                                   const BasicBlock *LoopPred) {
+  assert(PN.getBasicBlockIndex(LoopPred) >= 0 &&
+         "LoopPred must be a predecessor of the phi's block");
+  if (PN.getNumIncomingValues() != 2)
+    return {nullptr, nullptr};
+  unsigned StartIdx = PN.getIncomingBlock(0) == LoopPred ? 0 : 1;
+  return {PN.getIncomingValue(StartIdx), PN.getIncomingValue(1 - StartIdx)};
+}
+
+std::pair<bool, bool> State::getNonDecreasingInfo(PHINode &PN, Value *Start,
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dtcxzyw wrote:

Start is unused.


https://github.com/llvm/llvm-project/pull/216764