[PATCH] D113656: [LICM] Check a heuristic case to hoist load

[Florian Hahn via Phabricator via llvm-commits]

fhahn added inline comments.


================
Comment at: llvm/lib/Transforms/Scalar/LICM.cpp:2407
+  // ; MemoryUse(2) MayAlias
+  //   %0 = load i32**, i32*** @a, align 8, !tbaa !8
+  //   %idxprom = zext i32 %i.0 to i64
----------------
is `!tbaa` required here?

Also, would it be possible that `@a` contains the address of `@a` before we enter the loop? Could the first store in the loop modify `@a` that way?


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Comment at: llvm/lib/Transforms/Scalar/LICM.cpp:2466
+  auto *PtrDiffSCEV = SE->getMinusSCEV(StorePtrSCEV, LoadSCEV);
+  if (dyn_cast<SCEVAddRecExpr>(PtrDiffSCEV))
+    return false;
----------------
is this sufficient? An addrec could have an unknown step I think, which could be 0.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D113656/new/

https://reviews.llvm.org/D113656