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

[William Moses via llvm-commits]

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@@ -9076,12 +9198,134 @@ ScalarEvolution::ExitLimit ScalarEvolution::computeExitLimitFromICmp(
 
   const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
   const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
+  if (!AssumeLoopExists) {
+    ExitLimit EL = computeExitLimitFromICmp(L, Pred, LHS, RHS, ControlsOnlyExit,
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wsmoses wrote:

Things to integrate into `computeExitLimitFromICmp`

at the start of the function, if `AssumeLoopExits` do the same prop_phi stuff.

and also in switch statement add support for LE / GE like below

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