[llvm] [DA] Extract duplicated logic from gcdMIVtest (PR #152688)

[Ryotaro Kasuga via llvm-commits]

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@@ -2345,6 +2345,43 @@ static std::optional<APInt> getConstantPart(const SCEV *Expr) {
   return std::nullopt;
 }
 
+bool DependenceInfo::accumulateCoefficientsGCD(const SCEV *Expr,
+                                               const Loop *CurLoop,
+                                               const SCEV *&CurLoopCoeff,
+                                               APInt &RunningGCD) const {
+  // If RunningGCD is already 1, exit early.
+  // TODO: It might be better to continue the recursion to find CurLoopCoeff.
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kasuga-fj wrote:

This seems pretty buggy. Considering that `DstCoeff` is initialized to something like zero, we may not be able to distinguish between the case where `Dst` is invariant in `CurLoop` and the case where `Dst` is NOT invariant but the GCD is 1.

https://github.com/llvm/llvm-project/pull/152688