1 files changed, 16 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 2693f45..290f367 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -1561,6 +1561,21 @@ bool WidenIV::widenWithVariantUse(WidenIV::NarrowIVDefUse DU) {
     return true;
   }
 
+  // We'll prove some facts that should be true in the context of ext users. If
+  // there is no users, we are done now. If there are some, pick their common
+  // dominator as context.
+  Instruction *Context = nullptr;
+  for (auto *Ext : ExtUsers) {
+    if (!Context || DT->dominates(Ext, Context))
+      Context = Ext;
+    else if (!DT->dominates(Context, Ext))
+      // For users that don't have dominance relation, use common dominator.
+      Context =
+          DT->findNearestCommonDominator(Context->getParent(), Ext->getParent())
+              ->getTerminator();
+  }
+  assert(Context && "Context not found?");
+
   if (!CanSignExtend && !CanZeroExtend) {
     // Because InstCombine turns 'sub nuw' to 'add' losing the no-wrap flag, we
     // will most likely not see it. Let's try to prove it.
@@ -1573,7 +1588,7 @@ bool WidenIV::widenWithVariantUse(WidenIV::NarrowIVDefUse DU) {
     if (!SE->isKnownNegative(RHS))
       return false;
     bool ProvedSubNUW = SE->isKnownPredicateAt(
-        ICmpInst::ICMP_UGE, LHS, SE->getNegativeSCEV(RHS), NarrowUse);
+        ICmpInst::ICMP_UGE, LHS, SE->getNegativeSCEV(RHS), Context);
     if (!ProvedSubNUW)
       return false;
     // In fact, our 'add' is 'sub nuw'. We will need to widen the 2nd operand as