Move LSR's private isZero function to a public SCEV member

function, and make use of it in several places.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52463 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/ScalarEvolution.h

@@ -81,6 +81,10 @@ namespace llvm {
     /// 
     uint32_t getBitWidth() const;
 
+    /// isZero - Return true if the expression is a constant zero.
+    ///
+    bool isZero() const;
+
     /// replaceSymbolicValuesWithConcrete - If this SCEV internally references
     /// the symbolic value "Sym", construct and return a new SCEV that produces
     /// the same value, but which uses the concrete value Conc instead of the

lib/Analysis/ScalarEvolution.cpp

@@ -132,6 +132,12 @@ uint32_t SCEV::getBitWidth() const {
   return 0;
 }
 
+bool SCEV::isZero() const {
+  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
+    return SC->getValue()->isZero();
+  return false;
+}
+
 
 SCEVCouldNotCompute::SCEVCouldNotCompute() : SCEV(scCouldNotCompute) {}
 
@@ -1136,11 +1142,10 @@ SCEVHandle ScalarEvolution::getAddRecExpr(std::vector<SCEVHandle> &Operands,
                                const Loop *L) {
   if (Operands.size() == 1) return Operands[0];
 
-  if (SCEVConstant *StepC = dyn_cast<SCEVConstant>(Operands.back()))
+  if (Operands.back()->isZero()) {
-    if (StepC->getValue()->isZero()) {
+    Operands.pop_back();
-      Operands.pop_back();
+    return getAddRecExpr(Operands, L);             // { X,+,0 }  -->  X
-      return getAddRecExpr(Operands, L);             // { X,+,0 }  -->  X
+  }
-    }
 
   SCEVAddRecExpr *&Result =
     (*SCEVAddRecExprs)[std::make_pair(L, std::vector<SCEV*>(Operands.begin(),
@@ -2583,9 +2588,8 @@ SCEVHandle ScalarEvolutionsImpl::HowFarToZero(SCEV *V, const Loop *L) {
         // value at this index.  When solving for "X*X != 5", for example, we
         // should not accept a root of 2.
         SCEVHandle Val = AddRec->evaluateAtIteration(R1, SE);
-        if (SCEVConstant *EvalVal = dyn_cast<SCEVConstant>(Val))
+        if (Val->isZero())
-          if (EvalVal->getValue()->isZero())
+          return R1;  // We found a quadratic root!
-            return R1;  // We found a quadratic root!
       }
     }
   }

lib/Analysis/ScalarEvolutionExpander.cpp

@@ -126,8 +126,7 @@ Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
   assert(Ty->isInteger() && "Cannot expand fp recurrences yet!");
 
   // {X,+,F} --> X + {0,+,F}
-  if (!isa<SCEVConstant>(S->getStart()) ||
+  if (!S->getStart()->isZero()) {
-      !cast<SCEVConstant>(S->getStart())->getValue()->isZero()) {
     Value *Start = expand(S->getStart());
     std::vector<SCEVHandle> NewOps(S->op_begin(), S->op_end());
     NewOps[0] = SE.getIntegerSCEV(0, Ty);

lib/Transforms/Scalar/LoopStrengthReduce.cpp

@@ -586,9 +586,8 @@ Value *BasedUser::InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
   }
   
   // If there is no immediate value, skip the next part.
-  if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Imm))
+  if (Imm->isZero())
-    if (SC->getValue()->isZero())
+    return Rewriter.expandCodeFor(NewBase, BaseInsertPt);
-      return Rewriter.expandCodeFor(NewBase, BaseInsertPt);
 
   Value *Base = Rewriter.expandCodeFor(NewBase, BaseInsertPt);
 
@@ -891,8 +890,7 @@ static void SeparateSubExprs(std::vector<SCEVHandle> &SubExprs,
 
       SeparateSubExprs(SubExprs, SARE->getOperand(0), SE);
     }
-  } else if (!isa<SCEVConstant>(Expr) ||
+  } else if (!Expr->isZero()) {
-             !cast<SCEVConstant>(Expr)->getValue()->isZero()) {
     // Do not add zero.
     SubExprs.push_back(Expr);
   }
@@ -979,14 +977,6 @@ RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses,
   return Result;
 }
 
-/// isZero - returns true if the scalar evolution expression is zero.
-///
-static bool isZero(const SCEVHandle &V) {
-  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(V))
-    return SC->getValue()->isZero();
-  return false;
-}
-
 /// ValidStride - Check whether the given Scale is valid for all loads and 
 /// stores in UsersToProcess.
 ///
@@ -1009,7 +999,7 @@ bool LoopStrengthReduce::ValidStride(bool HasBaseReg,
     TargetLowering::AddrMode AM;
     if (SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
       AM.BaseOffs = SC->getValue()->getSExtValue();
-    AM.HasBaseReg = HasBaseReg || !isZero(UsersToProcess[i].Base);
+    AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
     AM.Scale = Scale;
 
     // If load[imm+r*scale] is illegal, bail out.
@@ -1069,7 +1059,7 @@ unsigned LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
                IE = SI->second.IVs.end(); II != IE; ++II)
           // FIXME: Only handle base == 0 for now.
           // Only reuse previous IV if it would not require a type conversion.
-          if (isZero(II->Base) &&
+          if (II->Base->isZero() &&
               !RequiresTypeConversion(II->Base->getType(), Ty)) {
             IV = *II;
             return Scale;
@@ -1233,7 +1223,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
   // their value in a register and add it in for each use. This will take up
   // a register operand, which potentially restricts what stride values are
   // valid.
-  bool HaveCommonExprs = !isZero(CommonExprs);
+  bool HaveCommonExprs = !CommonExprs->isZero();
   
   // If all uses are addresses, check if it is possible to reuse an IV with a
   // stride that is a factor of this stride. And that the multiple is a number
@@ -1629,7 +1619,7 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
       // Avoid rewriting the compare instruction with an iv of new stride
       // if it's likely the new stride uses will be rewritten using the
       if (AllUsesAreAddresses &&
-          ValidStride(!isZero(CommonExprs), Scale, UsersToProcess)) {        
+          ValidStride(!CommonExprs->isZero(), Scale, UsersToProcess)) {
         NewCmpVal = CmpVal;
         continue;
       }