Disallow the construction of SCEVs with could-not-compute operands. Catch CNCs

returned by BinomialCoefficient and don't try to operate with them. This
replaces the previous fix for PR2857.

llvm-svn: 57431

lib/Analysis/ScalarEvolution.cpp

@@ -644,11 +644,12 @@ SCEVHandle SCEVAddRecExpr::evaluateAtIteration(SCEVHandle It,
     // The computation is correct in the face of overflow provided that the
     // multiplication is performed _after_ the evaluation of the binomial
     // coefficient.
-    SCEVHandle Val =
+    SCEVHandle Coeff = BinomialCoefficient(It, i, SE,
-      SE.getMulExpr(getOperand(i),
+                                           cast<IntegerType>(getType()));
-                    BinomialCoefficient(It, i, SE,
+    if (isa<SCEVCouldNotCompute>(Coeff))
-                                        cast<IntegerType>(getType())));
+      return Coeff;
-    Result = SE.getAddExpr(Result, Val);
+
+    Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
   }
   return Result;
 }
@@ -676,9 +677,6 @@ SCEVHandle ScalarEvolution::getTruncateExpr(const SCEVHandle &Op, const Type *Ty
       return getAddRecExpr(Operands, AddRec->getLoop());
   }
 
-  if (isa<SCEVCouldNotCompute>(Op))
-    return new SCEVCouldNotCompute();
-
   SCEVTruncateExpr *&Result = (*SCEVTruncates)[std::make_pair(Op, Ty)];
   if (Result == 0) Result = new SCEVTruncateExpr(Op, Ty);
   return Result;
@@ -694,9 +692,6 @@ SCEVHandle ScalarEvolution::getZeroExtendExpr(const SCEVHandle &Op, const Type *
   // operands (often constants).  This would allow analysis of something like
   // this:  for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
 
-  if (isa<SCEVCouldNotCompute>(Op))
-    return new SCEVCouldNotCompute();
-
   SCEVZeroExtendExpr *&Result = (*SCEVZeroExtends)[std::make_pair(Op, Ty)];
   if (Result == 0) Result = new SCEVZeroExtendExpr(Op, Ty);
   return Result;
@@ -712,9 +707,6 @@ SCEVHandle ScalarEvolution::getSignExtendExpr(const SCEVHandle &Op, const Type *
   // operands (often constants).  This would allow analysis of something like
   // this:  for (signed char X = 0; X < 100; ++X) { int Y = X; }
 
-  if (isa<SCEVCouldNotCompute>(Op))
-    return new SCEVCouldNotCompute();
-
   SCEVSignExtendExpr *&Result = (*SCEVSignExtends)[std::make_pair(Op, Ty)];
   if (Result == 0) Result = new SCEVSignExtendExpr(Op, Ty);
   return Result;
@@ -743,10 +735,6 @@ SCEVHandle ScalarEvolution::getAddExpr(std::vector<SCEVHandle> &Ops) {
   // Sort by complexity, this groups all similar expression types together.
   GroupByComplexity(Ops);
 
-  // Could not compute plus anything equals could not compute.
-  if (isa<SCEVCouldNotCompute>(Ops.back()))
-    return new SCEVCouldNotCompute();
-
   // If there are any constants, fold them together.
   unsigned Idx = 0;
   if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@@ -972,21 +960,6 @@ SCEVHandle ScalarEvolution::getMulExpr(std::vector<SCEVHandle> &Ops) {
   // Sort by complexity, this groups all similar expression types together.
   GroupByComplexity(Ops);
 
-  if (isa<SCEVCouldNotCompute>(Ops.back())) {
-    // CNC * 0 = 0
-    for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
-      if (Ops[i]->getSCEVType() != scConstant)
-        break;
-
-      SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
-      if (SC->getValue()->isMinValue(false))
-        return SC;
-    }
-
-    // Otherwise, we can't compute it.
-    return new SCEVCouldNotCompute();
-  }
-
   // If there are any constants, fold them together.
   unsigned Idx = 0;
   if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@@ -1152,9 +1125,6 @@ SCEVHandle ScalarEvolution::getUDivExpr(const SCEVHandle &LHS, const SCEVHandle
 
   // FIXME: implement folding of (X*4)/4 when we know X*4 doesn't overflow.
 
-  if (isa<SCEVCouldNotCompute>(LHS) || isa<SCEVCouldNotCompute>(RHS))
-    return new SCEVCouldNotCompute();
-
   SCEVUDivExpr *&Result = (*SCEVUDivs)[std::make_pair(LHS, RHS)];
   if (Result == 0) Result = new SCEVUDivExpr(LHS, RHS);
   return Result;
@@ -1202,12 +1172,6 @@ SCEVHandle ScalarEvolution::getAddRecExpr(std::vector<SCEVHandle> &Operands,
     }
   }
 
-  // Refuse to build an AddRec out of SCEVCouldNotCompute.
-  for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
-    if (isa<SCEVCouldNotCompute>(Operands[i]))
-      return new SCEVCouldNotCompute();
-  }
-
   SCEVAddRecExpr *&Result =
     (*SCEVAddRecExprs)[std::make_pair(L, std::vector<SCEV*>(Operands.begin(),
                                                             Operands.end()))];
@@ -1230,21 +1194,6 @@ SCEVHandle ScalarEvolution::getSMaxExpr(std::vector<SCEVHandle> Ops) {
   // Sort by complexity, this groups all similar expression types together.
   GroupByComplexity(Ops);
 
-  if (isa<SCEVCouldNotCompute>(Ops.back())) {
-    // CNC smax +inf = +inf.
-    for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
-      if (Ops[i]->getSCEVType() != scConstant)
-        break;
-
-      SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
-      if (SC->getValue()->isMaxValue(true))
-        return SC;
-    }
-
-    // Otherwise, we can't compute it.
-    return new SCEVCouldNotCompute();
-  }
-
   // If there are any constants, fold them together.
   unsigned Idx = 0;
   if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@@ -1325,21 +1274,6 @@ SCEVHandle ScalarEvolution::getUMaxExpr(std::vector<SCEVHandle> Ops) {
   // Sort by complexity, this groups all similar expression types together.
   GroupByComplexity(Ops);
 
-  if (isa<SCEVCouldNotCompute>(Ops[0])) {
-    // CNC umax inf = inf.
-    for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
-      if (Ops[i]->getSCEVType() != scConstant)
-        break;
-
-      SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
-      if (SC->getValue()->isMaxValue(false))
-        return SC;
-    }
-
-    // Otherwise, we can't compute it.
-    return new SCEVCouldNotCompute();
-  }
-
   // If there are any constants, fold them together.
   unsigned Idx = 0;
   if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {