[llvm] [DA] do not handle array accesses of different offsets (PR #123436)

[Michael Kruse via llvm-commits]

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@@ -3649,6 +3646,111 @@ DependenceInfo::depends(Instruction *Src, Instruction *Dst) {
     LLVM_DEBUG(dbgs() << "can't analyze SCEV with different pointer base\n");
     return std::make_unique<Dependence>(Src, Dst);
   }
+
+  auto EltSize = SrcLoc.Size.toRaw();
+  assert(EltSize == DstLoc.Size.toRaw() && "Array element size differ");
+
+  // Check that memory access offsets in V are multiples of array EltSize.
+  std::function<bool(const SCEV *, const SCEV *&)> checkOffsets =
+      [&](const SCEV *V, const SCEV *&Param) -> bool {
+    if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
+      if (!checkOffsets(AddRec->getStart(), Param))
+        return false;
+      return checkOffsets(AddRec->getStepRecurrence(*SE), Param);
+    }
+    if (auto *Cst = dyn_cast<SCEVConstant>(V)) {
+      APInt C = Cst->getAPInt();
+      return C.srem(EltSize) == 0;
+    }
+
+    auto checkParamsMultipleOfSize = [&](const SCEV *V,
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Meinersbur wrote:

Lambda-within-lamda?

https://github.com/llvm/llvm-project/pull/123436