[llvm] [SCEV] Collect guard info for ICMP NE w/o constants. (PR #160500)

[Nikita Popov via llvm-commits]

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@@ -15873,6 +15873,16 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
           const SCEV *OneAlignedUp =
               DividesBy ? GetNextSCEVDividesByDivisor(One, DividesBy) : One;
           To = SE.getUMaxExpr(FromRewritten, OneAlignedUp);
+        } else {
+          if (LHS->getType()->isPointerTy()) {
+            LHS = SE.getLosslessPtrToIntExpr(LHS);
+            RHS = SE.getLosslessPtrToIntExpr(RHS);
+            if (isa<SCEVCouldNotCompute>(LHS) || isa<SCEVCouldNotCompute>(RHS))
+              break;
+          }
+          From = SE.getMinusSCEV(RHS, LHS);
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nikic wrote:

Hm, wouldn't we have to add this for both RHS - LHS and LHS - RHS? Otherwise the guard will or will not work depending on whether you write RHS != LHS or LHS != RHS.

https://github.com/llvm/llvm-project/pull/160500