Merging r324195:

------------------------------------------------------------------------
r324195 | mcrosier | 2018-02-04 16:42:24 +0100 (Sun, 04 Feb 2018) | 12 lines

[LV] Use Demanded Bits and ValueTracking for reduction type-shrinking

The type-shrinking logic in reduction detection, although narrow in scope, is
also rather ad-hoc, which has led to bugs (e.g., PR35734). This patch modifies
the approach to rely on the demanded bits and value tracking analyses, if
available. We currently perform type-shrinking separately for reductions and
other instructions in the loop. Long-term, we should probably think about
computing minimal bit widths in a more complete way for the loops we want to
vectorize.

PR35734
Differential Revision: https://reviews.llvm.org/D42309
------------------------------------------------------------------------


git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_60@325508 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 210 insertions, 102 deletions

diff --git a/include/llvm/Transforms/Utils/LoopUtils.h b/include/llvm/Transforms/Utils/LoopUtils.h
index 75066613650..fb53647112f 100644
--- a/include/llvm/Transforms/Utils/LoopUtils.h
+++ b/include/llvm/Transforms/Utils/LoopUtils.h
@@ -21,6 +21,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/DemandedBits.h"
 #include "llvm/Analysis/EHPersonalities.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/Dominators.h"
@@ -172,15 +173,25 @@ public:
                                Value *Left, Value *Right);
 
   /// Returns true if Phi is a reduction of type Kind and adds it to the
-  /// RecurrenceDescriptor.
+  /// RecurrenceDescriptor. If either \p DB is non-null or \p AC and \p DT are
+  /// non-null, the minimal bit width needed to compute the reduction will be
+  /// computed.
   static bool AddReductionVar(PHINode *Phi, RecurrenceKind Kind, Loop *TheLoop,
                               bool HasFunNoNaNAttr,
-                              RecurrenceDescriptor &RedDes);
-
-  /// Returns true if Phi is a reduction in TheLoop. The RecurrenceDescriptor is
-  /// returned in RedDes.
+                              RecurrenceDescriptor &RedDes,
+                              DemandedBits *DB = nullptr,
+                              AssumptionCache *AC = nullptr,
+                              DominatorTree *DT = nullptr);
+
+  /// Returns true if Phi is a reduction in TheLoop. The RecurrenceDescriptor
+  /// is returned in RedDes. If either \p DB is non-null or \p AC and \p DT are
+  /// non-null, the minimal bit width needed to compute the reduction will be
+  /// computed.
   static bool isReductionPHI(PHINode *Phi, Loop *TheLoop,
-                             RecurrenceDescriptor &RedDes);
+                             RecurrenceDescriptor &RedDes,
+                             DemandedBits *DB = nullptr,
+                             AssumptionCache *AC = nullptr,
+                             DominatorTree *DT = nullptr);
 
   /// Returns true if Phi is a first-order recurrence. A first-order recurrence
   /// is a non-reduction recurrence relation in which the value of the
@@ -218,24 +229,6 @@ public:
   /// Returns true if the recurrence kind is an arithmetic kind.
   static bool isArithmeticRecurrenceKind(RecurrenceKind Kind);
 
-  /// Determines if Phi may have been type-promoted. If Phi has a single user
-  /// that ANDs the Phi with a type mask, return the user. RT is updated to
-  /// account for the narrower bit width represented by the mask, and the AND
-  /// instruction is added to CI.
-  static Instruction *lookThroughAnd(PHINode *Phi, Type *&RT,
-                                     SmallPtrSetImpl<Instruction *> &Visited,
-                                     SmallPtrSetImpl<Instruction *> &CI);
-
-  /// Returns true if all the source operands of a recurrence are either
-  /// SExtInsts or ZExtInsts. This function is intended to be used with
-  /// lookThroughAnd to determine if the recurrence has been type-promoted. The
-  /// source operands are added to CI, and IsSigned is updated to indicate if
-  /// all source operands are SExtInsts.
-  static bool getSourceExtensionKind(Instruction *Start, Instruction *Exit,
-                                     Type *RT, bool &IsSigned,
-                                     SmallPtrSetImpl<Instruction *> &Visited,
-                                     SmallPtrSetImpl<Instruction *> &CI);
-
   /// Returns the type of the recurrence. This type can be narrower than the
   /// actual type of the Phi if the recurrence has been type-promoted.
   Type *getRecurrenceType() { return RecurrenceType; }
diff --git a/lib/Transforms/Utils/LoopUtils.cpp b/lib/Transforms/Utils/LoopUtils.cpp
index a5a305ef582..0a357f4b500 100644
--- a/lib/Transforms/Utils/LoopUtils.cpp
+++ b/lib/Transforms/Utils/LoopUtils.cpp
@@ -23,6 +23,7 @@
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
@@ -30,6 +31,7 @@
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/KnownBits.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 
 using namespace llvm;
@@ -77,10 +79,13 @@ bool RecurrenceDescriptor::isArithmeticRecurrenceKind(RecurrenceKind Kind) {
   return false;
 }
 
-Instruction *
-RecurrenceDescriptor::lookThroughAnd(PHINode *Phi, Type *&RT,
-                                     SmallPtrSetImpl<Instruction *> &Visited,
-                                     SmallPtrSetImpl<Instruction *> &CI) {
+/// Determines if Phi may have been type-promoted. If Phi has a single user
+/// that ANDs the Phi with a type mask, return the user. RT is updated to
+/// account for the narrower bit width represented by the mask, and the AND
+/// instruction is added to CI.
+static Instruction *lookThroughAnd(PHINode *Phi, Type *&RT,
+                                   SmallPtrSetImpl<Instruction *> &Visited,
+                                   SmallPtrSetImpl<Instruction *> &CI) {
   if (!Phi->hasOneUse())
     return Phi;
 
@@ -101,70 +106,92 @@ RecurrenceDescriptor::lookThroughAnd(PHINode *Phi, Type *&RT,
   return Phi;
 }
 
-bool RecurrenceDescriptor::getSourceExtensionKind(
-    Instruction *Start, Instruction *Exit, Type *RT, bool &IsSigned,
-    SmallPtrSetImpl<Instruction *> &Visited,
-    SmallPtrSetImpl<Instruction *> &CI) {
+/// Compute the minimal bit width needed to represent a reduction whose exit
+/// instruction is given by Exit.
+static std::pair<Type *, bool> computeRecurrenceType(Instruction *Exit,
+                                                     DemandedBits *DB,
+                                                     AssumptionCache *AC,
+                                                     DominatorTree *DT) {
+  bool IsSigned = false;
+  const DataLayout &DL = Exit->getModule()->getDataLayout();
+  uint64_t MaxBitWidth = DL.getTypeSizeInBits(Exit->getType());
+
+  if (DB) {
+    // Use the demanded bits analysis to determine the bits that are live out
+    // of the exit instruction, rounding up to the nearest power of two. If the
+    // use of demanded bits results in a smaller bit width, we know the value
+    // must be positive (i.e., IsSigned = false), because if this were not the
+    // case, the sign bit would have been demanded.
+    auto Mask = DB->getDemandedBits(Exit);
+    MaxBitWidth = Mask.getBitWidth() - Mask.countLeadingZeros();
+  }
+
+  if (MaxBitWidth == DL.getTypeSizeInBits(Exit->getType()) && AC && DT) {
+    // If demanded bits wasn't able to limit the bit width, we can try to use
+    // value tracking instead. This can be the case, for example, if the value
+    // may be negative.
+    auto NumSignBits = ComputeNumSignBits(Exit, DL, 0, AC, nullptr, DT);
+    auto NumTypeBits = DL.getTypeSizeInBits(Exit->getType());
+    MaxBitWidth = NumTypeBits - NumSignBits;
+    KnownBits Bits = computeKnownBits(Exit, DL);
+    if (!Bits.isNonNegative()) {
+      // If the value is not known to be non-negative, we set IsSigned to true,
+      // meaning that we will use sext instructions instead of zext
+      // instructions to restore the original type.
+      IsSigned = true;
+      if (!Bits.isNegative())
+        // If the value is not known to be negative, we don't known what the
+        // upper bit is, and therefore, we don't know what kind of extend we
+        // will need. In this case, just increase the bit width by one bit and
+        // use sext.
+        ++MaxBitWidth;
+    }
+  }
+  if (!isPowerOf2_64(MaxBitWidth))
+    MaxBitWidth = NextPowerOf2(MaxBitWidth);
+
+  return std::make_pair(Type::getIntNTy(Exit->getContext(), MaxBitWidth),
+                        IsSigned);
+}
+
+/// Collect cast instructions that can be ignored in the vectorizer's cost
+/// model, given a reduction exit value and the minimal type in which the
+/// reduction can be represented.
+static void collectCastsToIgnore(Loop *TheLoop, Instruction *Exit,
+                                 Type *RecurrenceType,
+                                 SmallPtrSetImpl<Instruction *> &Casts) {
 
   SmallVector<Instruction *, 8> Worklist;
-  bool FoundOneOperand = false;
-  unsigned DstSize = RT->getPrimitiveSizeInBits();
+  SmallPtrSet<Instruction *, 8> Visited;
   Worklist.push_back(Exit);
 
-  // Traverse the instructions in the reduction expression, beginning with the
-  // exit value.
   while (!Worklist.empty()) {
-    Instruction *I = Worklist.pop_back_val();
-    for (Use &U : I->operands()) {
-
-      // Terminate the traversal if the operand is not an instruction, or we
-      // reach the starting value.
-      Instruction *J = dyn_cast<Instruction>(U.get());
-      if (!J || J == Start)
-        continue;
-
-      // Otherwise, investigate the operation if it is also in the expression.
-      if (Visited.count(J)) {
-        Worklist.push_back(J);
+    Instruction *Val = Worklist.pop_back_val();
+    Visited.insert(Val);
+    if (auto *Cast = dyn_cast<CastInst>(Val))
+      if (Cast->getSrcTy() == RecurrenceType) {
+        // If the source type of a cast instruction is equal to the recurrence
+        // type, it will be eliminated, and should be ignored in the vectorizer
+        // cost model.
+        Casts.insert(Cast);
         continue;
       }
 
-      // If the operand is not in Visited, it is not a reduction operation, but
-      // it does feed into one. Make sure it is either a single-use sign- or
-      // zero-extend instruction.
-      CastInst *Cast = dyn_cast<CastInst>(J);
-      bool IsSExtInst = isa<SExtInst>(J);
-      if (!Cast || !Cast->hasOneUse() || !(isa<ZExtInst>(J) || IsSExtInst))
-        return false;
-
-      // Ensure the source type of the extend is no larger than the reduction
-      // type. It is not necessary for the types to be identical.
-      unsigned SrcSize = Cast->getSrcTy()->getPrimitiveSizeInBits();
-      if (SrcSize > DstSize)
-        return false;
-
-      // Furthermore, ensure that all such extends are of the same kind.
-      if (FoundOneOperand) {
-        if (IsSigned != IsSExtInst)
-          return false;
-      } else {
-        FoundOneOperand = true;
-        IsSigned = IsSExtInst;
-      }
-
-      // Lastly, if the source type of the extend matches the reduction type,
-      // add the extend to CI so that we can avoid accounting for it in the
-      // cost model.
-      if (SrcSize == DstSize)
-        CI.insert(Cast);
-    }
+    // Add all operands to the work list if they are loop-varying values that
+    // we haven't yet visited.
+    for (Value *O : cast<User>(Val)->operands())
+      if (auto *I = dyn_cast<Instruction>(O))
+        if (TheLoop->contains(I) && !Visited.count(I))
+          Worklist.push_back(I);
   }
-  return true;
 }
 
 bool RecurrenceDescriptor::AddReductionVar(PHINode *Phi, RecurrenceKind Kind,
                                            Loop *TheLoop, bool HasFunNoNaNAttr,
-                                           RecurrenceDescriptor &RedDes) {
+                                           RecurrenceDescriptor &RedDes,
+                                           DemandedBits *DB,
+                                           AssumptionCache *AC,
+                                           DominatorTree *DT) {
   if (Phi->getNumIncomingValues() != 2)
     return false;
 
@@ -353,14 +380,49 @@ bool RecurrenceDescriptor::AddReductionVar(PHINode *Phi, RecurrenceKind Kind,
   if (!FoundStartPHI || !FoundReduxOp || !ExitInstruction)
     return false;
 
-  // If we think Phi may have been type-promoted, we also need to ensure that
-  // all source operands of the reduction are either SExtInsts or ZEstInsts. If
-  // so, we will be able to evaluate the reduction in the narrower bit width.
-  if (Start != Phi)
-    if (!getSourceExtensionKind(Start, ExitInstruction, RecurrenceType,
-                                IsSigned, VisitedInsts, CastInsts))
+  if (Start != Phi) {
+    // If the starting value is not the same as the phi node, we speculatively
+    // looked through an 'and' instruction when evaluating a potential
+    // arithmetic reduction to determine if it may have been type-promoted.
+    //
+    // We now compute the minimal bit width that is required to represent the
+    // reduction. If this is the same width that was indicated by the 'and', we
+    // can represent the reduction in the smaller type. The 'and' instruction
+    // will be eliminated since it will essentially be a cast instruction that
+    // can be ignore in the cost model. If we compute a different type than we
+    // did when evaluating the 'and', the 'and' will not be eliminated, and we
+    // will end up with different kinds of operations in the recurrence
+    // expression (e.g., RK_IntegerAND, RK_IntegerADD). We give up if this is
+    // the case.
+    //
+    // The vectorizer relies on InstCombine to perform the actual
+    // type-shrinking. It does this by inserting instructions to truncate the
+    // exit value of the reduction to the width indicated by RecurrenceType and
+    // then extend this value back to the original width. If IsSigned is false,
+    // a 'zext' instruction will be generated; otherwise, a 'sext' will be
+    // used.
+    //
+    // TODO: We should not rely on InstCombine to rewrite the reduction in the
+    //       smaller type. We should just generate a correctly typed expression
+    //       to begin with.
+    Type *ComputedType;
+    std::tie(ComputedType, IsSigned) =
+        computeRecurrenceType(ExitInstruction, DB, AC, DT);
+    if (ComputedType != RecurrenceType)
       return false;
 
+    // The recurrence expression will be represented in a narrower type. If
+    // there are any cast instructions that will be unnecessary, collect them
+    // in CastInsts. Note that the 'and' instruction was already included in
+    // this list.
+    //
+    // TODO: A better way to represent this may be to tag in some way all the
+    //       instructions that are a part of the reduction. The vectorizer cost
+    //       model could then apply the recurrence type to these instructions,
+    //       without needing a white list of instructions to ignore.
+    collectCastsToIgnore(TheLoop, ExitInstruction, RecurrenceType, CastInsts);
+  }
+
   // We found a reduction var if we have reached the original phi node and we
   // only have a single instruction with out-of-loop users.
 
@@ -480,47 +542,57 @@ bool RecurrenceDescriptor::hasMultipleUsesOf(
   return false;
 }
 bool RecurrenceDescriptor::isReductionPHI(PHINode *Phi, Loop *TheLoop,
-                                          RecurrenceDescriptor &RedDes) {
+                                          RecurrenceDescriptor &RedDes,
+                                          DemandedBits *DB, AssumptionCache *AC,
+                                          DominatorTree *DT) {
 
   BasicBlock *Header = TheLoop->getHeader();
   Function &F = *Header->getParent();
   bool HasFunNoNaNAttr =
       F.getFnAttribute("no-nans-fp-math").getValueAsString() == "true";
 
-  if (AddReductionVar(Phi, RK_IntegerAdd, TheLoop, HasFunNoNaNAttr, RedDes)) {
+  if (AddReductionVar(Phi, RK_IntegerAdd, TheLoop, HasFunNoNaNAttr, RedDes, DB,
+                      AC, DT)) {
     DEBUG(dbgs() << "Found an ADD reduction PHI." << *Phi << "\n");
     return true;
   }
-  if (AddReductionVar(Phi, RK_IntegerMult, TheLoop, HasFunNoNaNAttr, RedDes)) {
+  if (AddReductionVar(Phi, RK_IntegerMult, TheLoop, HasFunNoNaNAttr, RedDes, DB,
+                      AC, DT)) {
     DEBUG(dbgs() << "Found a MUL reduction PHI." << *Phi << "\n");
     return true;
   }
-  if (AddReductionVar(Phi, RK_IntegerOr, TheLoop, HasFunNoNaNAttr, RedDes)) {
+  if (AddReductionVar(Phi, RK_IntegerOr, TheLoop, HasFunNoNaNAttr, RedDes, DB,
+                      AC, DT)) {
     DEBUG(dbgs() << "Found an OR reduction PHI." << *Phi << "\n");
     return true;
   }
-  if (AddReductionVar(Phi, RK_IntegerAnd, TheLoop, HasFunNoNaNAttr, RedDes)) {
+  if (AddReductionVar(Phi, RK_IntegerAnd, TheLoop, HasFunNoNaNAttr, RedDes, DB,
+                      AC, DT)) {
     DEBUG(dbgs() << "Found an AND reduction PHI." << *Phi << "\n");
     return true;
   }
-  if (AddReductionVar(Phi, RK_IntegerXor, TheLoop, HasFunNoNaNAttr, RedDes)) {
+  if (AddReductionVar(Phi, RK_IntegerXor, TheLoop, HasFunNoNaNAttr, RedDes, DB,
+                      AC, DT)) {
     DEBUG(dbgs() << "Found a XOR reduction PHI." << *Phi << "\n");
     return true;
   }
-  if (AddReductionVar(Phi, RK_IntegerMinMax, TheLoop, HasFunNoNaNAttr,
-                      RedDes)) {
+  if (AddReductionVar(Phi, RK_IntegerMinMax, TheLoop, HasFunNoNaNAttr, RedDes,
+                      DB, AC, DT)) {
     DEBUG(dbgs() << "Found a MINMAX reduction PHI." << *Phi << "\n");
     return true;
   }
-  if (AddReductionVar(Phi, RK_FloatMult, TheLoop, HasFunNoNaNAttr, RedDes)) {
+  if (AddReductionVar(Phi, RK_FloatMult, TheLoop, HasFunNoNaNAttr, RedDes, DB,
+                      AC, DT)) {
     DEBUG(dbgs() << "Found an FMult reduction PHI." << *Phi << "\n");
     return true;
   }
-  if (AddReductionVar(Phi, RK_FloatAdd, TheLoop, HasFunNoNaNAttr, RedDes)) {
+  if (AddReductionVar(Phi, RK_FloatAdd, TheLoop, HasFunNoNaNAttr, RedDes, DB,
+                      AC, DT)) {
     DEBUG(dbgs() << "Found an FAdd reduction PHI." << *Phi << "\n");
     return true;
   }
-  if (AddReductionVar(Phi, RK_FloatMinMax, TheLoop, HasFunNoNaNAttr, RedDes)) {
+  if (AddReductionVar(Phi, RK_FloatMinMax, TheLoop, HasFunNoNaNAttr, RedDes, DB,
+                      AC, DT)) {
     DEBUG(dbgs() << "Found an float MINMAX reduction PHI." << *Phi << "\n");
     return true;
   }
diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 64f206ea92e..5bcf0c0a7ba 100644
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1542,9 +1542,10 @@ public:
       const TargetTransformInfo *TTI,
       std::function<const LoopAccessInfo &(Loop &)> *GetLAA, LoopInfo *LI,
       OptimizationRemarkEmitter *ORE, LoopVectorizationRequirements *R,
-      LoopVectorizeHints *H)
+      LoopVectorizeHints *H, DemandedBits *DB, AssumptionCache *AC)
       : TheLoop(L), PSE(PSE), TLI(TLI), TTI(TTI), DT(DT), GetLAA(GetLAA),
-        ORE(ORE), InterleaveInfo(PSE, L, DT, LI), Requirements(R), Hints(H) {}
+        ORE(ORE), InterleaveInfo(PSE, L, DT, LI), Requirements(R), Hints(H),
+        DB(DB), AC(AC) {}
 
   /// ReductionList contains the reduction descriptors for all
   /// of the reductions that were found in the loop.
@@ -1833,6 +1834,14 @@ private:
   /// Used to emit an analysis of any legality issues.
   LoopVectorizeHints *Hints;
 
+  /// The demanded bits analsyis is used to compute the minimum type size in
+  /// which a reduction can be computed.
+  DemandedBits *DB;
+
+  /// The assumption cache analysis is used to compute the minimum type size in
+  /// which a reduction can be computed.
+  AssumptionCache *AC;
+
   /// While vectorizing these instructions we have to generate a
   /// call to the appropriate masked intrinsic
   SmallPtrSet<const Instruction *, 8> MaskedOp;
@@ -5300,7 +5309,8 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
         }
 
         RecurrenceDescriptor RedDes;
-        if (RecurrenceDescriptor::isReductionPHI(Phi, TheLoop, RedDes)) {
+        if (RecurrenceDescriptor::isReductionPHI(Phi, TheLoop, RedDes, DB, AC,
+                                                 DT)) {
           if (RedDes.hasUnsafeAlgebra())
             Requirements->addUnsafeAlgebraInst(RedDes.getUnsafeAlgebraInst());
           AllowedExit.insert(RedDes.getLoopExitInstr());
@@ -8514,7 +8524,7 @@ bool LoopVectorizePass::processLoop(Loop *L) {
   // Check if it is legal to vectorize the loop.
   LoopVectorizationRequirements Requirements(*ORE);
   LoopVectorizationLegality LVL(L, PSE, DT, TLI, AA, F, TTI, GetLAA, LI, ORE,
-                                &Requirements, &Hints);
+                                &Requirements, &Hints, DB, AC);
   if (!LVL.canVectorize()) {
     DEBUG(dbgs() << "LV: Not vectorizing: Cannot prove legality.\n");
     emitMissedWarning(F, L, Hints, ORE);
diff --git a/test/Transforms/LoopVectorize/reduction-small-size.ll b/test/Transforms/LoopVectorize/reduction-small-size.ll
index b44beb8ce68..879f1c3c5ad 100644
--- a/test/Transforms/LoopVectorize/reduction-small-size.ll
+++ b/test/Transforms/LoopVectorize/reduction-small-size.ll
@@ -14,7 +14,7 @@ target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 ; CHECK-NEXT:    [[TMP17]] = zext <4 x i8> [[TMP16]] to <4 x i32>
 ; CHECK-NEXT:    br i1 {{.*}}, label %middle.block, label %vector.body
 ;
-define void @PR34687(i1 %c, i32 %x, i32 %n) {
+define i8 @PR34687(i1 %c, i32 %x, i32 %n) {
 entry:
   br label %for.body
 
@@ -36,5 +36,38 @@ if.end:
 
 for.end:
   %tmp2 = phi i32 [ %r.next, %if.end ]
-  ret void
+  %tmp3 = trunc i32 %tmp2 to i8
+  ret i8 %tmp3
+}
+
+; CHECK-LABEL: @PR35734(
+; CHECK:       vector.ph:
+; CHECK:         [[TMP3:%.*]] = insertelement <4 x i32> zeroinitializer, i32 %y, i32 0
+; CHECK-NEXT:    br label %vector.body
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, %vector.ph ], [ [[INDEX_NEXT:%.*]], %vector.body ]
+; CHECK-NEXT:    [[VEC_PHI:%.*]] = phi <4 x i32> [ [[TMP3]], %vector.ph ], [ [[TMP9:%.*]], %vector.body ]
+; CHECK:         [[TMP5:%.*]] = and <4 x i32> [[VEC_PHI]], <i32 1, i32 1, i32 1, i32 1>
+; CHECK-NEXT:    [[TMP6:%.*]] = add <4 x i32> [[TMP5]], <i32 -1, i32 -1, i32 -1, i32 -1>
+; CHECK-NEXT:    [[INDEX_NEXT]] = add i32 [[INDEX]], 4
+; CHECK:         [[TMP8:%.*]] = trunc <4 x i32> [[TMP6]] to <4 x i1>
+; CHECK-NEXT:    [[TMP9]] = sext <4 x i1> [[TMP8]] to <4 x i32>
+; CHECK-NEXT:    br i1 {{.*}}, label %middle.block, label %vector.body
+;
+define i32 @PR35734(i32 %x, i32 %y) {
+entry:
+  br label %for.body
+
+for.body:
+  %i = phi i32 [ %x, %entry ], [ %i.next, %for.body ]
+  %r = phi i32 [ %y, %entry ], [ %r.next, %for.body ]
+  %tmp0 = and i32 %r, 1
+  %r.next = add i32 %tmp0, -1
+  %i.next = add nsw i32 %i, 1
+  %cond = icmp sgt i32 %i, 77
+  br i1 %cond, label %for.end, label %for.body
+
+for.end:
+  %tmp1 = phi i32 [ %r.next, %for.body ]
+  ret i32 %tmp1
 }