[llvm] change contents of ScalarEvolution from private to protected (PR #83052)

[Nikita Popov via llvm-commits]

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@@ -12733,38 +12983,50 @@ ScalarEvolution::howManyLessThans(const SCEV *LHS, const SCEV *RHS,
     if (auto *ZExt = dyn_cast<SCEVZeroExtendExpr>(LHS)) {
       const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(ZExt->getOperand());
       if (AR && AR->getLoop() == L && AR->isAffine()) {
-        auto canProveNUW = [&]() {
-          // We can use the comparison to infer no-wrap flags only if it fully
-          // controls the loop exit.
-          if (!ControlsOnlyExit)
-            return false;
-
-          if (!isLoopInvariant(RHS, L))
-            return false;
-
-          if (!isKnownNonZero(AR->getStepRecurrence(*this)))
-            // We need the sequence defined by AR to strictly increase in the
-            // unsigned integer domain for the logic below to hold.
-            return false;
-
-          const unsigned InnerBitWidth = getTypeSizeInBits(AR->getType());
-          const unsigned OuterBitWidth = getTypeSizeInBits(RHS->getType());
-          // If RHS <=u Limit, then there must exist a value V in the sequence
-          // defined by AR (e.g. {Start,+,Step}) such that V >u RHS, and
-          // V <=u UINT_MAX.  Thus, we must exit the loop before unsigned
-          // overflow occurs.  This limit also implies that a signed comparison
-          // (in the wide bitwidth) is equivalent to an unsigned comparison as
-          // the high bits on both sides must be zero.
-          APInt StrideMax = getUnsignedRangeMax(AR->getStepRecurrence(*this));
-          APInt Limit = APInt::getMaxValue(InnerBitWidth) - (StrideMax - 1);
-          Limit = Limit.zext(OuterBitWidth);
-          return getUnsignedRangeMax(applyLoopGuards(RHS, L)).ule(Limit);
-        };
-        auto Flags = AR->getNoWrapFlags();
-        if (!hasFlags(Flags, SCEV::FlagNUW) && canProveNUW())
-          Flags = setFlags(Flags, SCEV::FlagNUW);
+        if (!AssumeLoopExists) {
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nikic wrote:

Here also, sounds like this just wasn't backported to enyzme's fork?

https://github.com/llvm/llvm-project/pull/83052