Revert r251050 to fix miscompile when running Clang -O1

See bug for details: https://llvm.org/bugs/show_bug.cgi?id=25421
Some comparisons were incorrectly replaced with a constant value.

llvm-svn: 252231

1 files changed, 1 insertions, 56 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 0d4a62c9d80..4652e449f4b 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -7348,60 +7348,6 @@ ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
   return false;
 }
 
-bool ScalarEvolution::isKnownPredicateViaNoOverflow(ICmpInst::Predicate Pred,
-                                                    const SCEV *LHS,
-                                                    const SCEV *RHS) {
-
-  // Match Result to (X + Y)<ExpectedFlags> where Y is a constant integer.
-  // Return Y via OutY.
-  auto MatchBinaryAddToConst =
-      [this](const SCEV *Result, const SCEV *X, APInt &OutY,
-             SCEV::NoWrapFlags ExpectedFlags) {
-    const SCEV *NonConstOp, *ConstOp;
-    SCEV::NoWrapFlags FlagsPresent;
-
-    if (!splitBinaryAdd(Result, ConstOp, NonConstOp, FlagsPresent) ||
-        !isa<SCEVConstant>(ConstOp) || NonConstOp != X)
-      return false;
-
-    OutY = cast<SCEVConstant>(ConstOp)->getValue()->getValue();
-    return (FlagsPresent & ExpectedFlags) == ExpectedFlags;
-  };
-
-  APInt C;
-
-  switch (Pred) {
-  default:
-    break;
-
-  case ICmpInst::ICMP_SGE:
-    std::swap(LHS, RHS);
-  case ICmpInst::ICMP_SLE:
-    // X s<= (X + C)<nsw> if C >= 0
-    if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) && C.isNonNegative())
-      return true;
-
-    // (X + C)<nsw> s<= X if C <= 0
-    if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) &&
-        !C.isStrictlyPositive())
-      return true;
-
-  case ICmpInst::ICMP_SGT:
-    std::swap(LHS, RHS);
-  case ICmpInst::ICMP_SLT:
-    // X s< (X + C)<nsw> if C > 0
-    if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) &&
-        C.isStrictlyPositive())
-      return true;
-
-    // (X + C)<nsw> s< X if C < 0
-    if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) && C.isNegative())
-      return true;
-  }
-
-  return false;
-}
-
 bool ScalarEvolution::isKnownPredicateViaSplitting(ICmpInst::Predicate Pred,
                                                    const SCEV *LHS,
                                                    const SCEV *RHS) {
@@ -8058,8 +8004,7 @@ ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
       [this](ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS) {
     return isKnownPredicateWithRanges(Pred, LHS, RHS) ||
            IsKnownPredicateViaMinOrMax(*this, Pred, LHS, RHS) ||
-           IsKnownPredicateViaAddRecStart(*this, Pred, LHS, RHS) ||
-           isKnownPredicateViaNoOverflow(Pred, LHS, RHS);
+           IsKnownPredicateViaAddRecStart(*this, Pred, LHS, RHS);
   };
 
   switch (Pred) {