[llvm-branch-commits] [llvm] [DA] Overflow check in WeakCrossing Delta calculation (PR #185046)

[Ehsan Amiri via llvm-branch-commits]

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@@ -1383,7 +1383,10 @@ bool DependenceInfo::weakCrossingSIVtest(const SCEVAddRecExpr *Src,
   ++WeakCrossingSIVapplications;
   assert(0 < Level && Level <= CommonLevels && "Level out of range");
   Level--;
-  const SCEV *Delta = SE->getMinusSCEV(DstConst, SrcConst);
+  const SCEV *Delta = minusSCEVNoSignedOverflow(DstConst, SrcConst, *SE);
+  if (Delta == nullptr)
+    return false;
+
   LLVM_DEBUG(dbgs() << "\t    Delta = " << *Delta << "\n");
   if (Delta->isZero()) {
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amehsan wrote:

We can also limit the test to constant values of `SrcConst` and `DstConst`. That may make things a bit simpler. The check already exists in line 1399-1401. So the only cases for which we may lose something are cases in which `SrcConst` and `DstConst` are symbolic, but their subtraction is zero.

I will update the code to cover this case.

https://github.com/llvm/llvm-project/pull/185046