Added SCEV::NoWrapFlags to manage unsigned, signed, and self wrap

properties.
Added the self-wrap flag for SCEV::AddRecExpr.
A slew of temporary FIXMEs indicate the intention of the no-self-wrap flag
without changing behavior in this revision.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127590 91177308-0d34-0410-b5e6-96231b3b80d8

7 files changed, 307 insertions, 182 deletions

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index d1938061be..651f989fe6 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -72,6 +72,29 @@ namespace llvm {
     void operator=(const SCEV &);  // DO NOT IMPLEMENT
 
   public:
+    /// NoWrapFlags are bitfield indices into SubclassData.
+    ///
+    /// Add and Mul expressions may have no-unsigned-wrap <NUW> or
+    /// no-signed-wrap <NSW> properties, which are derived from the IR
+    /// operator. NSW is a misnomer that we use to mean no signed overflow or
+    /// underflow.
+    ///
+    /// AddRec expression may have a no-self-wraparound <NW> property if the
+    /// result can never reach the start value. This property is independent of
+    /// the actual start value and step direction. Self-wraparound is defined
+    /// purely in terms of the recurrence's loop, step size, and
+    /// bitwidth. Formally, a recurrence with no self-wraparound satisfies:
+    /// abs(step) * max-iteration(loop) <= unsigned-max(bitwidth).
+    ///
+    /// Note that NUW and NSW are also valid properties of a recurrence, and
+    /// either implies NW. For convenience, NW will be set for a recurrence
+    /// whenever either NUW or NSW are set.
+    enum NoWrapFlags { FlagAnyWrap = 0,          // No guarantee.
+                       FlagNW      = (1 << 0),   // No self-wrap.
+                       FlagNUW     = (1 << 1),   // No unsigned wrap.
+                       FlagNSW     = (1 << 2),   // No signed wrap.
+                       NoWrapMask  = (1 << 3) -1 };
+
     explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) :
       FastID(ID), SCEVType(SCEVTy), SubclassData(0) {}
 
@@ -159,6 +182,20 @@ namespace llvm {
       ProperlyDominatesBlock ///< The SCEV properly dominates the block.
     };
 
+    /// Convenient NoWrapFlags manipulation that hides enum casts and is
+    /// visible in the ScalarEvolution name space.
+    static SCEV::NoWrapFlags maskFlags(SCEV::NoWrapFlags Flags, int Mask) {
+      return (SCEV::NoWrapFlags)(Flags & Mask);
+    }
+    static SCEV::NoWrapFlags setFlags(SCEV::NoWrapFlags Flags,
+                                      SCEV::NoWrapFlags OnFlags) {
+      return (SCEV::NoWrapFlags)(Flags | OnFlags);
+    }
+    static SCEV::NoWrapFlags clearFlags(SCEV::NoWrapFlags Flags,
+                                        SCEV::NoWrapFlags OffFlags) {
+      return (SCEV::NoWrapFlags)(Flags & ~OffFlags);
+    }
+
   private:
     /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be
     /// notified whenever a Value is deleted.
@@ -465,44 +502,41 @@ namespace llvm {
     const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty);
     const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty);
     const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
-                           bool HasNUW = false, bool HasNSW = false);
+                           SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
     const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS,
-                           bool HasNUW = false, bool HasNSW = false) {
+                           SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) {
       SmallVector<const SCEV *, 2> Ops;
       Ops.push_back(LHS);
       Ops.push_back(RHS);
-      return getAddExpr(Ops, HasNUW, HasNSW);
+      return getAddExpr(Ops, Flags);
     }
-    const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1,
-                           const SCEV *Op2,
-                           bool HasNUW = false, bool HasNSW = false) {
+    const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2,
+                           SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) {
       SmallVector<const SCEV *, 3> Ops;
       Ops.push_back(Op0);
       Ops.push_back(Op1);
       Ops.push_back(Op2);
-      return getAddExpr(Ops, HasNUW, HasNSW);
+      return getAddExpr(Ops, Flags);
     }
     const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
-                           bool HasNUW = false, bool HasNSW = false);
+                           SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
     const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS,
-                           bool HasNUW = false, bool HasNSW = false) {
+                           SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap)
+    {
       SmallVector<const SCEV *, 2> Ops;
       Ops.push_back(LHS);
       Ops.push_back(RHS);
-      return getMulExpr(Ops, HasNUW, HasNSW);
+      return getMulExpr(Ops, Flags);
     }
     const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS);
     const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step,
-                              const Loop *L,
-                              bool HasNUW = false, bool HasNSW = false);
+                              const Loop *L, SCEV::NoWrapFlags Flags);
     const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
-                              const Loop *L,
-                              bool HasNUW = false, bool HasNSW = false);
+                              const Loop *L, SCEV::NoWrapFlags Flags);
     const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands,
-                              const Loop *L,
-                              bool HasNUW = false, bool HasNSW = false) {
+                              const Loop *L, SCEV::NoWrapFlags Flags) {
       SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end());
-      return getAddRecExpr(NewOp, L, HasNUW, HasNSW);
+      return getAddRecExpr(NewOp, L, Flags);
     }
     const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS);
     const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
@@ -537,11 +571,9 @@ namespace llvm {
     ///
     const SCEV *getNotSCEV(const SCEV *V);
 
-    /// getMinusSCEV - Return LHS-RHS.  Minus is represented in SCEV as A+B*-1,
-    /// and thus the HasNUW and HasNSW bits apply to the resultant add, not
-    /// whether the sub would have overflowed.
+    /// getMinusSCEV - Return LHS-RHS.  Minus is represented in SCEV as A+B*-1.
     const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
-                             bool HasNUW = false, bool HasNSW = false);
+                             SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
 
     /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion
     /// of the input value to the specified type.  If the type must be
diff --git a/include/llvm/Analysis/ScalarEvolutionExpressions.h b/include/llvm/Analysis/ScalarEvolutionExpressions.h
index db432c8173..856d92c97c 100644
--- a/include/llvm/Analysis/ScalarEvolutionExpressions.h
+++ b/include/llvm/Analysis/ScalarEvolutionExpressions.h
@@ -160,13 +160,8 @@ namespace llvm {
 
     const Type *getType() const { return getOperand(0)->getType(); }
 
-    bool hasNoUnsignedWrap() const { return SubclassData & (1 << 0); }
-    void setHasNoUnsignedWrap(bool B) {
-      SubclassData = (SubclassData & ~(1 << 0)) | (B << 0);
-    }
-    bool hasNoSignedWrap() const { return SubclassData & (1 << 1); }
-    void setHasNoSignedWrap(bool B) {
-      SubclassData = (SubclassData & ~(1 << 1)) | (B << 1);
+    NoWrapFlags getNoWrapFlags(NoWrapFlags Mask = NoWrapMask) const {
+      return (NoWrapFlags)(SubclassData & Mask);
     }
 
     /// Methods for support type inquiry through isa, cast, and dyn_cast:
@@ -199,6 +194,11 @@ namespace llvm {
              S->getSCEVType() == scSMaxExpr ||
              S->getSCEVType() == scUMaxExpr;
     }
+
+    /// Set flags for a non-recurrence without clearing previously set flags.
+    void setNoWrapFlags(NoWrapFlags Flags) {
+      SubclassData |= Flags;
+    }
   };
 
 
@@ -305,11 +305,12 @@ namespace llvm {
     /// getStepRecurrence - This method constructs and returns the recurrence
     /// indicating how much this expression steps by.  If this is a polynomial
     /// of degree N, it returns a chrec of degree N-1.
+    /// We cannot determine whether the step recurrence has self-wraparound.
     const SCEV *getStepRecurrence(ScalarEvolution &SE) const {
       if (isAffine()) return getOperand(1);
       return SE.getAddRecExpr(SmallVector<const SCEV *, 3>(op_begin()+1,
                                                            op_end()),
-                              getLoop());
+                              getLoop(), FlagAnyWrap);
     }
 
     /// isAffine - Return true if this is an affine AddRec (i.e., it represents
@@ -327,6 +328,15 @@ namespace llvm {
       return getNumOperands() == 3;
     }
 
+    /// Set flags for a recurrence without clearing any previously set flags.
+    /// For AddRec, either NUW or NSW implies NW. Keep track of this fact here
+    /// to make it easier to propagate flags.
+    void setNoWrapFlags(NoWrapFlags Flags) {
+      if (Flags & (FlagNUW | FlagNSW))
+        Flags = ScalarEvolution::setFlags(Flags, FlagNW);
+      SubclassData |= Flags;
+    }
+
     /// evaluateAtIteration - Return the value of this chain of recurrences at
     /// the specified iteration number.
     const SCEV *evaluateAtIteration(const SCEV *It, ScalarEvolution &SE) const;
@@ -364,8 +374,7 @@ namespace llvm {
                  const SCEV *const *O, size_t N)
       : SCEVCommutativeExpr(ID, scSMaxExpr, O, N) {
       // Max never overflows.
-      setHasNoUnsignedWrap(true);
-      setHasNoSignedWrap(true);
+      setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW));
     }
 
   public:
@@ -387,8 +396,7 @@ namespace llvm {
                  const SCEV *const *O, size_t N)
       : SCEVCommutativeExpr(ID, scUMaxExpr, O, N) {
       // Max never overflows.
-      setHasNoUnsignedWrap(true);
-      setHasNoSignedWrap(true);
+      setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW));
     }
 
   public:
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 3cf2815e7b..a28f8ddbf4 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -157,10 +157,13 @@ void SCEV::print(raw_ostream &OS) const {
     for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
       OS << ",+," << *AR->getOperand(i);
     OS << "}<";
-    if (AR->hasNoUnsignedWrap())
+    if (AR->getNoWrapFlags(FlagNUW))
       OS << "nuw><";
-    if (AR->hasNoSignedWrap())
+    if (AR->getNoWrapFlags(FlagNSW))
       OS << "nsw><";
+    if (AR->getNoWrapFlags(FlagNW) &&
+        !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
+      OS << "nw><";
     WriteAsOperand(OS, AR->getLoop()->getHeader(), /*PrintType=*/false);
     OS << ">";
     return;
@@ -830,7 +833,7 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
       Operands.push_back(S);
     }
     if (!hasTrunc)
-      return getAddExpr(Operands, false, false);
+      return getAddExpr(Operands);
     UniqueSCEVs.FindNodeOrInsertPos(ID, IP);  // Mutates IP, returns NULL.
   }
 
@@ -845,7 +848,7 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
       Operands.push_back(S);
     }
     if (!hasTrunc)
-      return getMulExpr(Operands, false, false);
+      return getMulExpr(Operands);
     UniqueSCEVs.FindNodeOrInsertPos(ID, IP);  // Mutates IP, returns NULL.
   }
 
@@ -854,7 +857,7 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
     SmallVector<const SCEV *, 4> Operands;
     for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
       Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
-    return getAddRecExpr(Operands, AddRec->getLoop());
+    return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
   }
 
   // As a special case, fold trunc(undef) to undef. We don't want to
@@ -926,10 +929,11 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
 
       // If we have special knowledge that this addrec won't overflow,
       // we don't need to do any further analysis.
-      if (AR->hasNoUnsignedWrap())
+      if (AR->getNoWrapFlags(SCEV::FlagNUW))
         return getAddRecExpr(getZeroExtendExpr(Start, Ty),
                              getZeroExtendExpr(Step, Ty),
-                             L);
+                             // FIXME: Can use SCEV::FlagNUW
+                             L, SCEV::FlagAnyWrap);
 
       // Check whether the backedge-taken count is SCEVCouldNotCompute.
       // Note that this serves two purposes: It filters out loops that are
@@ -963,7 +967,8 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
             // Return the expression with the addrec on the outside.
             return getAddRecExpr(getZeroExtendExpr(Start, Ty),
                                  getZeroExtendExpr(Step, Ty),
-                                 L);
+                                 // FIXME: can use FlagNUW
+                                 L, SCEV::FlagAnyWrap);
 
           // Similar to above, only this time treat the step value as signed.
           // This covers loops that count down.
@@ -977,7 +982,8 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
             // Return the expression with the addrec on the outside.
             return getAddRecExpr(getZeroExtendExpr(Start, Ty),
                                  getSignExtendExpr(Step, Ty),
-                                 L);
+                                 // FIXME: can use FlagNW
+                                 L, SCEV::FlagAnyWrap);
         }
 
         // If the backedge is guarded by a comparison with the pre-inc value
@@ -994,7 +1000,8 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
             // Return the expression with the addrec on the outside.
             return getAddRecExpr(getZeroExtendExpr(Start, Ty),
                                  getZeroExtendExpr(Step, Ty),
-                                 L);
+                                 // FIXME: can use FlagNUW
+                                 L, SCEV::FlagAnyWrap);
         } else if (isKnownNegative(Step)) {
           const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
                                       getSignedRange(Step).getSignedMin());
@@ -1002,10 +1009,12 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
               (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
                isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
                                            AR->getPostIncExpr(*this), N)))
-            // Return the expression with the addrec on the outside.
+            // Return the expression with the addrec on the outside.  The
+            // negative step causes unsigned wrap, but it still can't self-wrap.
             return getAddRecExpr(getZeroExtendExpr(Start, Ty),
                                  getSignExtendExpr(Step, Ty),
-                                 L);
+                                 // FIXME: can use FlagNW
+                                 L, SCEV::FlagAnyWrap);
         }
       }
     }
@@ -1080,10 +1089,11 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
 
       // If we have special knowledge that this addrec won't overflow,
       // we don't need to do any further analysis.
-      if (AR->hasNoSignedWrap())
+      if (AR->getNoWrapFlags(SCEV::FlagNSW))
         return getAddRecExpr(getSignExtendExpr(Start, Ty),
                              getSignExtendExpr(Step, Ty),
-                             L);
+                             // FIXME: can use SCEV::FlagNSW
+                             L, SCEV::FlagAnyWrap);
 
       // Check whether the backedge-taken count is SCEVCouldNotCompute.
       // Note that this serves two purposes: It filters out loops that are
@@ -1117,7 +1127,8 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
             // Return the expression with the addrec on the outside.
             return getAddRecExpr(getSignExtendExpr(Start, Ty),
                                  getSignExtendExpr(Step, Ty),
-                                 L);
+                                 // FIXME: can use SCEV::FlagNSW
+                                 L, SCEV::FlagAnyWrap);
 
           // Similar to above, only this time treat the step value as unsigned.
           // This covers loops that count up with an unsigned step.
@@ -1131,7 +1142,8 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
             // Return the expression with the addrec on the outside.
             return getAddRecExpr(getSignExtendExpr(Start, Ty),
                                  getZeroExtendExpr(Step, Ty),
-                                 L);
+                                 // FIXME: can use SCEV::FlagNSW
+                                 L, SCEV::FlagAnyWrap);
         }
 
         // If the backedge is guarded by a comparison with the pre-inc value
@@ -1148,7 +1160,8 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
             // Return the expression with the addrec on the outside.
             return getAddRecExpr(getSignExtendExpr(Start, Ty),
                                  getSignExtendExpr(Step, Ty),
-                                 L);
+                                 // FIXME: can use SCEV::FlagNSW
+                                 L, SCEV::FlagAnyWrap);
         } else if (isKnownNegative(Step)) {
           const SCEV *N = getConstant(APInt::getSignedMaxValue(BitWidth) -
                                       getSignedRange(Step).getSignedMin());
@@ -1159,7 +1172,8 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
             // Return the expression with the addrec on the outside.
             return getAddRecExpr(getSignExtendExpr(Start, Ty),
                                  getSignExtendExpr(Step, Ty),
-                                 L);
+                                 // FIXME: can use SCEV::FlagNSW
+                                 L, SCEV::FlagAnyWrap);
         }
       }
     }
@@ -1213,7 +1227,8 @@ const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
     for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
          I != E; ++I)
       Ops.push_back(getAnyExtendExpr(*I, Ty));
-    return getAddRecExpr(Ops, AR->getLoop());
+    // FIXME: can use AR->getNoWrapFlags(SCEV::FlagNW)
+    return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagAnyWrap);
   }
 
   // As a special case, fold anyext(undef) to undef. We don't want to
@@ -1334,7 +1349,9 @@ namespace {
 /// getAddExpr - Get a canonical add expression, or something simpler if
 /// possible.
 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
-                                        bool HasNUW, bool HasNSW) {
+                                        SCEV::NoWrapFlags Flags) {
+  assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&
+         "only nuw or nsw allowed");
   assert(!Ops.empty() && "Cannot get empty add!");
   if (Ops.size() == 1) return Ops[0];
 #ifndef NDEBUG
@@ -1344,8 +1361,8 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
            "SCEVAddExpr operand types don't match!");
 #endif
 
-  // If HasNSW is true and all the operands are non-negative, infer HasNUW.
-  if (!HasNUW && HasNSW) {
+  // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
+  if (!(Flags & SCEV::FlagNUW) && (Flags & SCEV::FlagNSW)) {
     bool All = true;
     for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
          E = Ops.end(); I != E; ++I)
@@ -1353,7 +1370,7 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
         All = false;
         break;
       }
-    if (All) HasNUW = true;
+    if (All) Flags = setFlags(Flags, SCEV::FlagNUW);
   }
 
   // Sort by complexity, this groups all similar expression types together.
@@ -1404,7 +1421,7 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
       FoundMatch = true;
     }
   if (FoundMatch)
-    return getAddExpr(Ops, HasNUW, HasNSW);
+    return getAddExpr(Ops, Flags);
 
   // Check for truncates. If all the operands are truncated from the same
   // type, see if factoring out the truncate would permit the result to be
@@ -1454,7 +1471,7 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
     }
     if (Ok) {
       // Evaluate the expression in the larger type.
-      const SCEV *Fold = getAddExpr(LargeOps, HasNUW, HasNSW);
+      const SCEV *Fold = getAddExpr(LargeOps, Flags);
       // If it folds to something simple, use it. Otherwise, don't.
       if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
         return getTruncateExpr(Fold, DstType);
@@ -1625,9 +1642,10 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
 
       // Build the new addrec. Propagate the NUW and NSW flags if both the
       // outer add and the inner addrec are guaranteed to have no overflow.
-      const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop,
-                                         HasNUW && AddRec->hasNoUnsignedWrap(),
-                                         HasNSW && AddRec->hasNoSignedWrap());
+      // FIXME: Always propagate NW
+      //        AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW))
+      Flags = AddRec->getNoWrapFlags(Flags);
+      const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
 
       // If all of the other operands were loop invariant, we are done.
       if (Ops.size() == 1) return NewRec;
@@ -1668,7 +1686,8 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
               }
               Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
             }
-        Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop);
+        // Step size has changed, so we cannot guarantee no self-wraparound.
+        Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
         return getAddExpr(Ops);
       }
 
@@ -1692,15 +1711,16 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
                                         O, Ops.size());
     UniqueSCEVs.InsertNode(S, IP);
   }
-  if (HasNUW) S->setHasNoUnsignedWrap(true);
-  if (HasNSW) S->setHasNoSignedWrap(true);
+  S->setNoWrapFlags(Flags);
   return S;
 }
 
 /// getMulExpr - Get a canonical multiply expression, or something simpler if
 /// possible.
 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
-                                        bool HasNUW, bool HasNSW) {
+                                        SCEV::NoWrapFlags Flags) {
+  assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
+         "only nuw or nsw allowed");
   assert(!Ops.empty() && "Cannot get empty mul!");
   if (Ops.size() == 1) return Ops[0];
 #ifndef NDEBUG
@@ -1710,8 +1730,8 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
            "SCEVMulExpr operand types don't match!");
 #endif
 
-  // If HasNSW is true and all the operands are non-negative, infer HasNUW.
-  if (!HasNUW && HasNSW) {
+  // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
+  if (!(Flags & SCEV::FlagNUW) && (Flags & SCEV::FlagNSW)) {
     bool All = true;
     for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
          E = Ops.end(); I != E; ++I)
@@ -1719,7 +1739,7 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
         All = false;
         break;
       }
-    if (All) HasNUW = true;
+    if (All) Flags = setFlags(Flags, SCEV::FlagNUW);
   }
 
   // Sort by complexity, this groups all similar expression types together.
@@ -1759,12 +1779,12 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
     } else if (Ops[0]->isAllOnesValue()) {
       // If we have a mul by -1 of an add, try distributing the -1 among the
       // add operands.
-      if (Ops.size() == 2)
+      if (Ops.size() == 2) {
         if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
           SmallVector<const SCEV *, 4> NewOps;
           bool AnyFolded = false;
-          for (SCEVAddRecExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
-               I != E; ++I) {
+          for (SCEVAddRecExpr::op_iterator I = Add->op_begin(),
+                 E = Add->op_end(); I != E; ++I) {
             const SCEV *Mul = getMulExpr(Ops[0], *I);
             if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
             NewOps.push_back(Mul);
@@ -1772,6 +1792,7 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
           if (AnyFolded)
             return getAddExpr(NewOps);
         }
+      }
     }
 
     if (Ops.size() == 1)
@@ -1831,9 +1852,11 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
 
       // Build the new addrec. Propagate the NUW and NSW flags if both the
       // outer mul and the inner addrec are guaranteed to have no overflow.
-      const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop,
-                                         HasNUW && AddRec->hasNoUnsignedWrap(),
-                                         HasNSW && AddRec->hasNoSignedWrap());
+      //
+      // No self-wrap cannot be guaranteed after changing the step size, but
+      // will be infered if either NUW or NSW is true.
+      Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
+      const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
 
       // If all of the other operands were loop invariant, we are done.
       if (Ops.size() == 1) return NewRec;
@@ -1869,7 +1892,8 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
                                                getMulExpr(G, B),
                                                getMulExpr(B, D));
               const SCEV *NewAddRec = getAddRecExpr(NewStart, NewStep,
-                                                    F->getLoop());
+                                                    F->getLoop(),
+                                                    SCEV::FlagAnyWrap);
               if (Ops.size() == 2) return NewAddRec;
               Ops[Idx] = AddRec = cast<SCEVAddRecExpr>(NewAddRec);
               Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
@@ -1897,8 +1921,7 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
                                         O, Ops.size());
     UniqueSCEVs.InsertNode(S, IP);
   }
-  if (HasNUW) S->setHasNoUnsignedWrap(true);
-  if (HasNSW) S->setHasNoSignedWrap(true);
+  S->setNoWrapFlags(Flags);
   return S;
 }
 
@@ -1938,11 +1961,13 @@ const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
               getZeroExtendExpr(AR, ExtTy) ==
               getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
                             getZeroExtendExpr(Step, ExtTy),
-                            AR->getLoop())) {
+                            AR->getLoop(), SCEV::FlagAnyWrap)) {
             SmallVector<const SCEV *, 4> Operands;
             for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
               Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
-            return getAddRecExpr(Operands, AR->getLoop());
+            return getAddRecExpr(Operands, AR->getLoop(),
+                                 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
+                                 SCEV::FlagAnyWrap);
           }
       // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
       if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
@@ -2006,27 +2031,27 @@ const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
 
 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
 /// Simplify the expression as much as possible.
-const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start,
-                                           const SCEV *Step, const Loop *L,
-                                           bool HasNUW, bool HasNSW) {
+const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
+                                           const Loop *L,
+                                           SCEV::NoWrapFlags Flags) {
   SmallVector<const SCEV *, 4> Operands;
   Operands.push_back(Start);
   if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
     if (StepChrec->getLoop() == L) {
       Operands.append(StepChrec->op_begin(), StepChrec->op_end());
-      return getAddRecExpr(Operands, L);
+      // FIXME: can use maskFlags(Flags, SCEV::FlagNW)
+      return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap);
     }
 
   Operands.push_back(Step);
-  return getAddRecExpr(Operands, L, HasNUW, HasNSW);
+  return getAddRecExpr(Operands, L, Flags);
 }
 
 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
 /// Simplify the expression as much as possible.
 const SCEV *
 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
-                               const Loop *L,
-                               bool HasNUW, bool HasNSW) {
+                               const Loop *L, SCEV::NoWrapFlags Flags) {
   if (Operands.size() == 1) return Operands[0];
 #ifndef NDEBUG
   const Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
@@ -2040,7 +2065,7 @@ ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
 
   if (Operands.back()->isZero()) {
     Operands.pop_back();
-    return getAddRecExpr(Operands, L, HasNUW, HasNSW); // {X,+,0}  -->  X
+    return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0}  -->  X
   }
 
   // It's tempting to want to call getMaxBackedgeTakenCount count here and
@@ -2049,8 +2074,8 @@ ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
   // meaningful BE count at this point (and if we don't, we'd be stuck
   // with a SCEVCouldNotCompute as the cached BE count).
 
-  // If HasNSW is true and all the operands are non-negative, infer HasNUW.
-  if (!HasNUW && HasNSW) {
+  // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
+  if (!(Flags & SCEV::FlagNUW) && (Flags & SCEV::FlagNSW)) {
     bool All = true;
     for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
          E = Operands.end(); I != E; ++I)
@@ -2058,7 +2083,7 @@ ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
         All = false;
         break;
       }
-    if (All) HasNUW = true;
+    if (All) Flags = setFlags(Flags, SCEV::FlagNUW);
   }
 
   // Canonicalize nested AddRecs in by nesting them in order of loop depth.
@@ -2081,16 +2106,31 @@ ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
           break;
         }
       if (AllInvariant) {
-        NestedOperands[0] = getAddRecExpr(Operands, L);
+        // Create a recurrence for the outer loop with the same step size.
+        //
+        // FIXME:
+        // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
+        // inner recurrence has the same property.
+        //   maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
+        SCEV::NoWrapFlags OuterFlags = SCEV::FlagAnyWrap;
+
+        NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
         AllInvariant = true;
         for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
           if (!isLoopInvariant(NestedOperands[i], NestedLoop)) {
             AllInvariant = false;
             break;
           }
-        if (AllInvariant)
+        if (AllInvariant) {
           // Ok, both add recurrences are valid after the transformation.
-          return getAddRecExpr(NestedOperands, NestedLoop, HasNUW, HasNSW);
+          //
+          // FIXME:
+          // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
+          // the outer recurrence has the same property.
+          //   maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
+          SCEV::NoWrapFlags InnerFlags = SCEV::FlagAnyWrap;
+          return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
+        }
       }
       // Reset Operands to its original state.
       Operands[0] = NestedAR;
@@ -2114,8 +2154,7 @@ ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
                                            O, Operands.size(), L);
     UniqueSCEVs.InsertNode(S, IP);
   }
-  if (HasNUW) S->setHasNoUnsignedWrap(true);
-  if (HasNSW) S->setHasNoSignedWrap(true);
+  S->setNoWrapFlags(Flags);
   return S;
 }
 
@@ -2510,17 +2549,17 @@ const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
   return getMinusSCEV(AllOnes, V);
 }
 
-/// getMinusSCEV - Return LHS-RHS.  Minus is represented in SCEV as A+B*-1,
-/// and thus the HasNUW and HasNSW bits apply to the resultant add, not
-/// whether the sub would have overflowed.
+/// getMinusSCEV - Return LHS-RHS.  Minus is represented in SCEV as A+B*-1.
+///
+/// FIXME: prohibit FlagNUW here, as soon as getMinusSCEVForExitTest goes.
 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
-                                          bool HasNUW, bool HasNSW) {
+                                          SCEV::NoWrapFlags Flags) {
   // Fast path: X - X --> 0.
   if (LHS == RHS)
     return getConstant(LHS->getType(), 0);
 
   // X - Y --> X + -Y
-  return getAddExpr(LHS, getNegativeSCEV(RHS), HasNUW, HasNSW);
+  return getAddExpr(LHS, getNegativeSCEV(RHS), Flags);
 }
 
 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
@@ -2773,44 +2812,35 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
             if (isLoopInvariant(Accum, L) ||
                 (isa<SCEVAddRecExpr>(Accum) &&
                  cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
-              bool HasNUW = false;
-              bool HasNSW = false;
+              SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
 
               // If the increment doesn't overflow, then neither the addrec nor
               // the post-increment will overflow.
               if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
                 if (OBO->hasNoUnsignedWrap())
-                  HasNUW = true;
+                  Flags = setFlags(Flags, SCEV::FlagNUW);
                 if (OBO->hasNoSignedWrap())
-                  HasNSW = true;
+                  Flags = setFlags(Flags, SCEV::FlagNSW);
               } else if (const GEPOperator *GEP =
-                            dyn_cast<GEPOperator>(BEValueV)) {
-                // If the increment is a GEP, then we know it won't perform a
-                // signed overflow, because the address space cannot be
-                // wrapped around.
-                //
-                // NOTE: This isn't strictly true, because you could have an
-                // object straddling the 2G address boundary in a 32-bit address
-                // space (for example).  We really want to model this as a "has
-                // no signed/unsigned wrap" where the base pointer is treated as
-                // unsigned and the increment is known to not have signed
-                // wrapping.
-                //
-                // This is a highly theoretical concern though, and this is good
-                // enough for all cases we know of at this point. :)
-                //
-                HasNSW |= GEP->isInBounds();
+                         dyn_cast<GEPOperator>(BEValueV)) {
+                // If the increment is an inbounds GEP, then we know the address
+                // space cannot be wrapped around. We cannot make any guarantee
+                // about signed or unsigned overflow because pointers are
+                // unsigned but we may have a negative index from the base
+                // pointer.
+                if (GEP->isInBounds())
+                  // FIXME: should be SCEV::FlagNW
+                  Flags = setFlags(Flags, SCEV::FlagNSW);
               }
 
               const SCEV *StartVal = getSCEV(StartValueV);
-              const SCEV *PHISCEV =
-                getAddRecExpr(StartVal, Accum, L, HasNUW, HasNSW);
+              const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
 
               // Since the no-wrap flags are on the increment, they apply to the
               // post-incremented value as well.
               if (isLoopInvariant(Accum, L))
                 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
-                                    Accum, L, HasNUW, HasNSW);
+                                    Accum, L, Flags);
 
               // Okay, for the entire analysis of this edge we assumed the PHI
               // to be symbolic.  We now need to go back and purge all of the
@@ -2834,8 +2864,11 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
             // initial step of the addrec evolution.
             if (StartVal == getMinusSCEV(AddRec->getOperand(0),
                                          AddRec->getOperand(1))) {
+              // FIXME: For constant StartVal, we should be able to infer
+              // no-wrap flags.
               const SCEV *PHISCEV =
-                 getAddRecExpr(StartVal, AddRec->getOperand(1), L);
+                getAddRecExpr(StartVal, AddRec->getOperand(1), L,
+                              SCEV::FlagAnyWrap);
 
               // Okay, for the entire analysis of this edge we assumed the PHI
               // to be symbolic.  We now need to go back and purge all of the
@@ -2899,8 +2932,9 @@ const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
       IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);