[llvm] [DA] use NSW arithmetic (PR #116632)

[Sebastian Pop via llvm-commits]

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@@ -3116,11 +3116,9 @@ const SCEV *DependenceInfo::addToCoefficient(const SCEV *Expr,
                                              const Loop *TargetLoop,
                                              const SCEV *Value) const {
   const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Expr);
-  if (!AddRec) // create a new addRec
-    return SE->getAddRecExpr(Expr,
-                             Value,
-                             TargetLoop,
-                             SCEV::FlagAnyWrap); // Worst case, with no info.
+  if (!AddRec)
+    return SE->getAddRecExpr(Expr, Value, TargetLoop, SCEV::FlagNSW);
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sebpop wrote:

Yes, the check for affine happens at the beginning of the dependence test, and then during the dep test.  
dep test crashes because new non-affine AddRecs are added to the constraints.
The patch does modify the 2 places that build the new AddRecs to follow the definition of affine in checkSubscript.

https://github.com/llvm/llvm-project/pull/116632