Revert "[IndVars] ICmpInst should not prevent IV widening"

This reverts commit 0c9c6ddf17bb01ae350a899b3395bb078aa0c62e.

We are seeing some failures with this patch locally. Not clear
if it's causing them or just triggering a problem in another
place. Reverting while investigating.

1 files changed, 2 insertions, 39 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index e281c66..d37fe74 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -1541,14 +1541,10 @@ bool WidenIV::widenWithVariantUse(WidenIV::NarrowIVDefUse DU) {
   bool CanZeroExtend = ExtKind == ZeroExtended && OBO->hasNoUnsignedWrap();
   auto AnotherOpExtKind = ExtKind;
 
-  // Check that all uses are either:
-  // - narrow def (in case of we are widening the IV increment);
-  // - single-input LCSSA Phis;
-  // - comparison of the chosen type;
-  // - extend of the chosen type (raison d'etre).
+  // Check that all uses are either s/zext, or narrow def (in case of we are
+  // widening the IV increment), or single-input LCSSA Phis.
   SmallVector<Instruction *, 4> ExtUsers;
   SmallVector<PHINode *, 4> LCSSAPhiUsers;
-  SmallVector<ICmpInst *, 4> ICmpUsers;
   for (Use &U : NarrowUse->uses()) {
     Instruction *User = cast<Instruction>(U.getUser());
     if (User == NarrowDef)
@@ -1562,19 +1558,6 @@ bool WidenIV::widenWithVariantUse(WidenIV::NarrowIVDefUse DU) {
       LCSSAPhiUsers.push_back(LCSSAPhi);
       continue;
     }
-    if (auto *ICmp = dyn_cast<ICmpInst>(User)) {
-      auto Pred = ICmp->getPredicate();
-      // We have 3 types of predicates: signed, unsigned and equality
-      // predicates. For equality, it's legal to widen icmp for either sign and
-      // zero extend. For sign extend, we can also do so for signed predicates,
-      // likeweise for zero extend we can widen icmp for unsigned predicates.
-      if (ExtKind == ZeroExtended && ICmpInst::isSigned(Pred))
-        return false;
-      if (ExtKind == SignExtended && ICmpInst::isUnsigned(Pred))
-        return false;
-      ICmpUsers.push_back(ICmp);
-      continue;
-    }
     if (ExtKind == SignExtended)
       User = dyn_cast<SExtInst>(User);
     else
@@ -1672,26 +1655,6 @@ bool WidenIV::widenWithVariantUse(WidenIV::NarrowIVDefUse DU) {
     User->replaceAllUsesWith(TruncPN);
     DeadInsts.emplace_back(User);
   }
-
-  for (ICmpInst *User : ICmpUsers) {
-    Builder.SetInsertPoint(User);
-    auto ExtendedOp = [&](Value * V)->Value * {
-      if (V == NarrowUse)
-        return WideBO;
-      if (ExtKind == ZeroExtended)
-        return Builder.CreateZExt(V, WideBO->getType());
-      else
-        return Builder.CreateSExt(V, WideBO->getType());
-    };
-    auto Pred = User->getPredicate();
-    auto *LHS = ExtendedOp(User->getOperand(0));
-    auto *RHS = ExtendedOp(User->getOperand(1));
-    auto *WideCmp =
-        Builder.CreateICmp(Pred, LHS, RHS, User->getName() + ".wide");
-    User->replaceAllUsesWith(WideCmp);
-    DeadInsts.emplace_back(User);
-  }
-
   return true;
 }