[llvm] [SCEV] Rework IncrementWrapFlags (PR #219559)

[Ramkumar Ramachandra via llvm-commits]

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@@ -15374,39 +15387,13 @@ const SCEVAddRecExpr *ScalarEvolution::convertSCEVToAddRecWithPredicates(
     SmallVectorImpl<const SCEVPredicate *> &Preds) {
   SmallVector<const SCEVPredicate *> TransformPreds;
   S = SCEVPredicateRewriter::rewrite(S, L, *this, &TransformPreds, nullptr);
-  auto *AddRec = dyn_cast<SCEVAddRecExpr>(S);
-
-  if (!AddRec)
-    return nullptr;
-
-  // Check if any of the transformed predicates is known to be false. In that
-  // case, it doesn't make sense to convert to a predicated AddRec, as the
-  // versioned loop will never execute.
-  for (const SCEVPredicate *Pred : TransformPreds) {
-    auto *WrapPred = dyn_cast<SCEVWrapPredicate>(Pred);
-    if (!WrapPred || WrapPred->getFlags() != SCEVWrapPredicate::IncrementNSSW)
-      continue;
-
-    const SCEVAddRecExpr *AddRecToCheck = WrapPred->getExpr();
-    const SCEV *ExitCount = getBackedgeTakenCount(AddRecToCheck->getLoop());
-    if (isa<SCEVCouldNotCompute>(ExitCount))
-      continue;
-
-    const SCEV *Step = AddRecToCheck->getStepRecurrence(*this);
-    if (!Step->isOne())
-      continue;
-
-    ExitCount = getTruncateOrSignExtend(ExitCount, Step->getType());
-    const SCEV *Add = getAddExpr(AddRecToCheck->getStart(), ExitCount);
-    if (isKnownPredicate(CmpInst::ICMP_SLT, Add, AddRecToCheck->getStart()))
-      return nullptr;
+  if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
+    // Since the transformation was successful, we can now transfer the SCEV
+    // predicates.
+    append_range(Preds, TransformPreds);
+    return AddRec;
   }
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artagnon wrote:

Split out as https://github.com/llvm/llvm-project/pull/225086.

https://github.com/llvm/llvm-project/pull/219559