1 files changed, 30 insertions, 6 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 960bd64830c..0b860418712 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -4732,6 +4732,30 @@ ScalarEvolution::createAddRecFromPHIWithCasts(const SCEVUnknown *SymbolicPHI) {
   return Rewrite;
 }
 
+// FIXME: This utility is currently required because the Rewriter currently 
+// does not rewrite this expression: 
+// {0, +, (sext ix (trunc iy to ix) to iy)} 
+// into {0, +, %step},
+// even when the following Equal predicate exists: 
+// "%step == (sext ix (trunc iy to ix) to iy)".
+bool PredicatedScalarEvolution::areAddRecsEqualWithPreds(
+    const SCEVAddRecExpr *AR1, const SCEVAddRecExpr *AR2) const {
+  if (AR1 == AR2)
+    return true;
+
+  auto areExprsEqual = [&](const SCEV *Expr1, const SCEV *Expr2) -> bool {
+    if (Expr1 != Expr2 && !Preds.implies(SE.getEqualPredicate(Expr1, Expr2)) &&
+        !Preds.implies(SE.getEqualPredicate(Expr2, Expr1)))
+      return false;
+    return true;
+  };
+
+  if (!areExprsEqual(AR1->getStart(), AR2->getStart()) ||
+      !areExprsEqual(AR1->getStepRecurrence(SE), AR2->getStepRecurrence(SE)))
+    return false;
+  return true;
+}
+
 /// A helper function for createAddRecFromPHI to handle simple cases.
 ///
 /// This function tries to find an AddRec expression for the simplest (yet most
@@ -4874,33 +4898,33 @@ const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
           // indices form a positive value.
           if (GEP->isInBounds() && GEP->getOperand(0) == PN) {
             Flags = setFlags(Flags, SCEV::FlagNW);
-  
+
             const SCEV *Ptr = getSCEV(GEP->getPointerOperand());
             if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr)))
               Flags = setFlags(Flags, SCEV::FlagNUW);
           }
-  
+
           // We cannot transfer nuw and nsw flags from subtraction
           // operations -- sub nuw X, Y is not the same as add nuw X, -Y
           // for instance.
         }
-  
+
         const SCEV *StartVal = getSCEV(StartValueV);
         const SCEV *PHISCEV = getAddRecExpr(StartVal, 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
         // entries for the scalars that use the symbolic expression.
         forgetSymbolicName(PN, SymbolicName);
         ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
-  
+
         // We can add Flags to the post-inc expression only if we
         // know that it is *undefined behavior* for BEValueV to
         // overflow.
         if (auto *BEInst = dyn_cast<Instruction>(BEValueV))
           if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L))
             (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags);
-  
+
         return PHISCEV;
       }
     }