[SCEV] Use APInt for DividesBy when collecting loop guard info (NFC).

Follow-up as suggested in llvm#162617.

Just use an APInt for DividesBy, as the existing code already operates
on APInt and thus handles the case of DividesBy being 1.

Author: fhahn

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -15633,47 +15633,32 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
           return false;
         };
 
-    // Checks whether Expr is a non-negative constant, and Divisor is a positive
-    // constant, and returns their APInt in ExprVal and in DivisorVal.
-    auto GetNonNegExprAndPosDivisor = [&](const SCEV *Expr, const SCEV *Divisor,
-                                          APInt &ExprVal, APInt &DivisorVal) {
-      auto *ConstExpr = dyn_cast<SCEVConstant>(Expr);
-      auto *ConstDivisor = dyn_cast<SCEVConstant>(Divisor);
-      if (!ConstExpr || !ConstDivisor)
-        return false;
-      ExprVal = ConstExpr->getAPInt();
-      DivisorVal = ConstDivisor->getAPInt();
-      return ExprVal.isNonNegative() && !DivisorVal.isNonPositive();
-    };
-
     // Return a new SCEV that modifies \p Expr to the closest number divides by
     // \p Divisor and greater or equal than Expr.
-    // For now, only handle constant Expr and Divisor.
+    // For now, only handle constant Expr.
     auto GetNextSCEVDividesByDivisor = [&](const SCEV *Expr,
-                                           const SCEV *Divisor) {
-      APInt ExprVal;
-      APInt DivisorVal;
-      if (!GetNonNegExprAndPosDivisor(Expr, Divisor, ExprVal, DivisorVal))
+                                           const APInt &DivisorVal) {
+      const APInt *ExprVal;
+      if (!match(Expr, m_scev_APInt(ExprVal)) || ExprVal->isNegative())
         return Expr;
-      APInt Rem = ExprVal.urem(DivisorVal);
-      if (!Rem.isZero())
-        // return the SCEV: Expr + Divisor - Expr % Divisor
-        return SE.getConstant(ExprVal + DivisorVal - Rem);
-      return Expr;
+      APInt Rem = ExprVal->urem(DivisorVal);
+      if (Rem.isZero())
+        return Expr;
+      // return the SCEV: Expr + Divisor - Expr % Divisor
+      return SE.getConstant(*ExprVal + DivisorVal - Rem);
     };
 
     // Return a new SCEV that modifies \p Expr to the closest number divides by
     // \p Divisor and less or equal than Expr.
-    // For now, only handle constant Expr and Divisor.
+    // For now, only handle constant Expr.
     auto GetPreviousSCEVDividesByDivisor = [&](const SCEV *Expr,
-                                               const SCEV *Divisor) {
-      APInt ExprVal;
-      APInt DivisorVal;
-      if (!GetNonNegExprAndPosDivisor(Expr, Divisor, ExprVal, DivisorVal))
+                                               const APInt &DivisorVal) {
+      const APInt *ExprVal;
+      if (!match(Expr, m_scev_APInt(ExprVal)) || ExprVal->isNegative())
         return Expr;
-      APInt Rem = ExprVal.urem(DivisorVal);
+      APInt Rem = ExprVal->urem(DivisorVal);
       // return the SCEV: Expr - Expr % Divisor
-      return SE.getConstant(ExprVal - Rem);
+      return SE.getConstant(*ExprVal - Rem);
     };
 
     // Apply divisibilty by \p Divisor on MinMaxExpr with constant values,
@@ -15682,6 +15667,11 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
     std::function<const SCEV *(const SCEV *, const SCEV *)>
         ApplyDivisibiltyOnMinMaxExpr = [&](const SCEV *MinMaxExpr,
                                            const SCEV *Divisor) {
+          auto *ConstDivisor = dyn_cast<SCEVConstant>(Divisor);
+          if (!ConstDivisor)
+            return MinMaxExpr;
+          const APInt &DivisorVal = ConstDivisor->getAPInt();
+
           const SCEV *MinMaxLHS = nullptr, *MinMaxRHS = nullptr;
           SCEVTypes SCTy;
           if (!IsMinMaxSCEVWithNonNegativeConstant(MinMaxExpr, SCTy, MinMaxLHS,
@@ -15692,8 +15682,8 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
           assert(SE.isKnownNonNegative(MinMaxLHS) &&
                  "Expected non-negative operand!");
           auto *DivisibleExpr =
-              IsMin ? GetPreviousSCEVDividesByDivisor(MinMaxLHS, Divisor)
-                    : GetNextSCEVDividesByDivisor(MinMaxLHS, Divisor);
+              IsMin ? GetPreviousSCEVDividesByDivisor(MinMaxLHS, DivisorVal)
+                    : GetNextSCEVDividesByDivisor(MinMaxLHS, DivisorVal);
           SmallVector<const SCEV *> Ops = {
               ApplyDivisibiltyOnMinMaxExpr(MinMaxRHS, Divisor), DivisibleExpr};
           return SE.getMinMaxExpr(SCTy, Ops);
@@ -15750,10 +15740,7 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
     };
 
     const SCEV *RewrittenLHS = GetMaybeRewritten(LHS);
-    const SCEV *DividesBy = nullptr;
-    const APInt &Multiple = SE.getConstantMultiple(RewrittenLHS);
-    if (!Multiple.isOne())
-      DividesBy = SE.getConstant(Multiple);
+    const APInt &DividesBy = SE.getConstantMultiple(RewrittenLHS);
 
     // Collect rewrites for LHS and its transitive operands based on the
     // condition.
@@ -15775,21 +15762,21 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
         [[fallthrough]];
       case CmpInst::ICMP_SLT: {
         RHS = SE.getMinusSCEV(RHS, One);
-        RHS = DividesBy ? GetPreviousSCEVDividesByDivisor(RHS, DividesBy) : RHS;
+        RHS = GetPreviousSCEVDividesByDivisor(RHS, DividesBy);
         break;
       }
       case CmpInst::ICMP_UGT:
       case CmpInst::ICMP_SGT:
         RHS = SE.getAddExpr(RHS, One);
-        RHS = DividesBy ? GetNextSCEVDividesByDivisor(RHS, DividesBy) : RHS;
+        RHS = GetNextSCEVDividesByDivisor(RHS, DividesBy);
         break;
       case CmpInst::ICMP_ULE:
       case CmpInst::ICMP_SLE:
-        RHS = DividesBy ? GetPreviousSCEVDividesByDivisor(RHS, DividesBy) : RHS;
+        RHS = GetPreviousSCEVDividesByDivisor(RHS, DividesBy);
         break;
       case CmpInst::ICMP_UGE:
       case CmpInst::ICMP_SGE:
-        RHS = DividesBy ? GetNextSCEVDividesByDivisor(RHS, DividesBy) : RHS;
+        RHS = GetNextSCEVDividesByDivisor(RHS, DividesBy);
         break;
       default:
         break;
@@ -15843,7 +15830,7 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
       case CmpInst::ICMP_NE:
         if (match(RHS, m_scev_Zero())) {
           const SCEV *OneAlignedUp =
-              DividesBy ? GetNextSCEVDividesByDivisor(One, DividesBy) : One;
+              GetNextSCEVDividesByDivisor(One, DividesBy);
           To = SE.getUMaxExpr(FromRewritten, OneAlignedUp);
         }
         break;