Revert "[Dominator] Add findNearestCommonDominator() for Instructions (NFC)"

This reverts commit 7f0de9573f758f5f9108795850337a5acbd17eef.

This is missing handling for !isReachableFromEntry() blocks, which
may be relevant for some callers. Revert for now.

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 4e83d2f..a7fe065 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -106,8 +106,13 @@ static Instruction *findCommonDominator(ArrayRef<Instruction *> Instructions,
                                         DominatorTree &DT) {
   Instruction *CommonDom = nullptr;
   for (auto *Insn : Instructions)
-    CommonDom =
-        CommonDom ? DT.findNearestCommonDominator(CommonDom, Insn) : Insn;
+    if (!CommonDom || DT.dominates(Insn, CommonDom))
+      CommonDom = Insn;
+    else if (!DT.dominates(CommonDom, Insn))
+      // If there is no dominance relation, use common dominator.
+      CommonDom =
+          DT.findNearestCommonDominator(CommonDom->getParent(),
+                                        Insn->getParent())->getTerminator();
   assert(CommonDom && "Common dominator not found?");
   return CommonDom;
 }