1 files changed, 22 insertions, 18 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 440fe07..31be7d6 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -1153,6 +1153,7 @@ protected:
 
   Instruction *widenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter,
                           PHINode *OrigPhi, PHINode *WidePhi);
+  void truncateIVUse(NarrowIVDefUse DU);
 
   bool widenLoopCompare(NarrowIVDefUse DU);
   bool widenWithVariantUse(NarrowIVDefUse DU);
@@ -1569,15 +1570,18 @@ WidenIV::WidenedRecTy WidenIV::getWideRecurrence(WidenIV::NarrowIVDefUse DU) {
 
 /// This IV user cannot be widened. Replace this use of the original narrow IV
 /// with a truncation of the new wide IV to isolate and eliminate the narrow IV.
-static void truncateIVUse(WidenIV::NarrowIVDefUse DU, DominatorTree *DT,
-                          LoopInfo *LI) {
+void WidenIV::truncateIVUse(NarrowIVDefUse DU) {
   auto *InsertPt = getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT, LI);
   if (!InsertPt)
     return;
   LLVM_DEBUG(dbgs() << "INDVARS: Truncate IV " << *DU.WideDef << " for user "
                     << *DU.NarrowUse << "\n");
+  ExtendKind ExtKind = getExtendKind(DU.NarrowDef);
   IRBuilder<> Builder(InsertPt);
-  Value *Trunc = Builder.CreateTrunc(DU.WideDef, DU.NarrowDef->getType());
+  Value *Trunc =
+      Builder.CreateTrunc(DU.WideDef, DU.NarrowDef->getType(), "",
+                          DU.NeverNegative || ExtKind == ExtendKind::Zero,
+                          DU.NeverNegative || ExtKind == ExtendKind::Sign);
   DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, Trunc);
 }
 
@@ -1826,6 +1830,13 @@ Instruction *WidenIV::widenIVUse(WidenIV::NarrowIVDefUse DU,
   assert(ExtendKindMap.count(DU.NarrowDef) &&
          "Should already know the kind of extension used to widen NarrowDef");
 
+  // This narrow use can be widened by a sext if it's non-negative or its narrow
+  // def was widened by a sext. Same for zext.
+  bool CanWidenBySExt =
+      DU.NeverNegative || getExtendKind(DU.NarrowDef) == ExtendKind::Sign;
+  bool CanWidenByZExt =
+      DU.NeverNegative || getExtendKind(DU.NarrowDef) == ExtendKind::Zero;
+
   // Stop traversing the def-use chain at inner-loop phis or post-loop phis.
   if (PHINode *UsePhi = dyn_cast<PHINode>(DU.NarrowUse)) {
     if (LI->getLoopFor(UsePhi->getParent()) != L) {
@@ -1833,7 +1844,7 @@ Instruction *WidenIV::widenIVUse(WidenIV::NarrowIVDefUse DU,
       // After SimplifyCFG most loop exit targets have a single predecessor.
       // Otherwise fall back to a truncate within the loop.
       if (UsePhi->getNumOperands() != 1)
-        truncateIVUse(DU, DT, LI);
+        truncateIVUse(DU);
       else {
         // Widening the PHI requires us to insert a trunc.  The logical place
         // for this trunc is in the same BB as the PHI.  This is not possible if
@@ -1847,7 +1858,8 @@ Instruction *WidenIV::widenIVUse(WidenIV::NarrowIVDefUse DU,
         WidePhi->addIncoming(DU.WideDef, UsePhi->getIncomingBlock(0));
         BasicBlock *WidePhiBB = WidePhi->getParent();
         IRBuilder<> Builder(WidePhiBB, WidePhiBB->getFirstInsertionPt());
-        Value *Trunc = Builder.CreateTrunc(WidePhi, DU.NarrowDef->getType());
+        Value *Trunc = Builder.CreateTrunc(WidePhi, DU.NarrowDef->getType(), "",
+                                           CanWidenByZExt, CanWidenBySExt);
         UsePhi->replaceAllUsesWith(Trunc);
         DeadInsts.emplace_back(UsePhi);
         LLVM_DEBUG(dbgs() << "INDVARS: Widen lcssa phi " << *UsePhi << " to "
@@ -1857,18 +1869,9 @@ Instruction *WidenIV::widenIVUse(WidenIV::NarrowIVDefUse DU,
     }
   }
 
-  // This narrow use can be widened by a sext if it's non-negative or its narrow
-  // def was widened by a sext. Same for zext.
-  auto canWidenBySExt = [&]() {
-    return DU.NeverNegative || getExtendKind(DU.NarrowDef) == ExtendKind::Sign;
-  };
-  auto canWidenByZExt = [&]() {
-    return DU.NeverNegative || getExtendKind(DU.NarrowDef) == ExtendKind::Zero;
-  };
-
   // Our raison d'etre! Eliminate sign and zero extension.
-  if ((match(DU.NarrowUse, m_SExtLike(m_Value())) && canWidenBySExt()) ||
-      (isa<ZExtInst>(DU.NarrowUse) && canWidenByZExt())) {
+  if ((match(DU.NarrowUse, m_SExtLike(m_Value())) && CanWidenBySExt) ||
+      (isa<ZExtInst>(DU.NarrowUse) && CanWidenByZExt)) {
     Value *NewDef = DU.WideDef;
     if (DU.NarrowUse->getType() != WideType) {
       unsigned CastWidth = SE->getTypeSizeInBits(DU.NarrowUse->getType());
@@ -1876,7 +1879,8 @@ Instruction *WidenIV::widenIVUse(WidenIV::NarrowIVDefUse DU,
       if (CastWidth < IVWidth) {
         // The cast isn't as wide as the IV, so insert a Trunc.
         IRBuilder<> Builder(DU.NarrowUse);
-        NewDef = Builder.CreateTrunc(DU.WideDef, DU.NarrowUse->getType());
+        NewDef = Builder.CreateTrunc(DU.WideDef, DU.NarrowUse->getType(), "",
+                                     CanWidenByZExt, CanWidenBySExt);
       }
       else {
         // A wider extend was hidden behind a narrower one. This may induce
@@ -1975,7 +1979,7 @@ Instruction *WidenIV::widenIVUse(WidenIV::NarrowIVDefUse DU,
   // This user does not evaluate to a recurrence after widening, so don't
   // follow it. Instead insert a Trunc to kill off the original use,
   // eventually isolating the original narrow IV so it can be removed.
-  truncateIVUse(DU, DT, LI);
+  truncateIVUse(DU);
   return nullptr;
 }