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

[Nikita Popov via llvm-commits]

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@@ -8947,37 +9067,39 @@ ScalarEvolution::ExitLimit ScalarEvolution::computeExitLimitFromCondImpl(
   // preserve the CFG and is temporarily leaving constant conditions
   // in place.
   if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
-    if (ExitIfTrue == !CI->getZExtValue())
+    if (ExitIfTrue == !CI->getZExtValue()) {
       // The backedge is always taken.
       return getCouldNotCompute();
+    }
     // The backedge is never taken.
     return getZero(CI->getType());
   }
 
-  // If we're exiting based on the overflow flag of an x.with.overflow intrinsic
-  // with a constant step, we can form an equivalent icmp predicate and figure
-  // out how many iterations will be taken before we exit.
-  const WithOverflowInst *WO;
-  const APInt *C;
-  if (match(ExitCond, m_ExtractValue<1>(m_WithOverflowInst(WO))) &&
-      match(WO->getRHS(), m_APInt(C))) {
-    ConstantRange NWR =
-      ConstantRange::makeExactNoWrapRegion(WO->getBinaryOp(), *C,
-                                           WO->getNoWrapKind());
-    CmpInst::Predicate Pred;
-    APInt NewRHSC, Offset;
-    NWR.getEquivalentICmp(Pred, NewRHSC, Offset);
-    if (!ExitIfTrue)
-      Pred = ICmpInst::getInversePredicate(Pred);
-    auto *LHS = getSCEV(WO->getLHS());
-    if (Offset != 0)
-      LHS = getAddExpr(LHS, getConstant(Offset));
-    auto EL = computeExitLimitFromICmp(L, Pred, LHS, getConstant(NewRHSC),
-                                       ControlsOnlyExit, AllowPredicates);
-    if (EL.hasAnyInfo())
-      return EL;
+  // block was never executed in MustExitScalarEvolution code
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nikic wrote:

Sounds like this improvement just wasn't backported to Enzyme's fork. You can drop this condition.

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