[PATCH] D143641: [MemorySSA] Iteratively check if gep's pointer operand is a guaranteed loop invariant

[Alina Sbirlea via Phabricator via llvm-commits]

asbirlea accepted this revision.
asbirlea added a comment.
This revision is now accepted and ready to land.

lgtm with comments addressed.



================
Comment at: llvm/lib/Analysis/MemorySSA.cpp:2629
+  // TODO: Increase limit?
+  const unsigned MaxGEPToLookup = 2;
+  for (unsigned I = 0; I < MaxGEPToLookup; I++) {
----------------
The AA "look through geps" limit is 6. I don't have a strong preference on the value, I don't have any data on how frequent this will be useful..
Would be good to use a cl::opt instead of a local constant though, for easier testing.


================
Comment at: llvm/lib/Analysis/MemorySSA.cpp:2640
+      }
+    } else
       return true;
----------------
nit: Could reduce the if nesting
```
auto *I = dyn_cast<Instruction>(Ptr);
if (!I || isa<AllocaInst>(Ptr) || I->getParent()->isEntryBlock())
  return true;
 
if (auto *GEP = dyn_cast<GEPOperator>(Ptr)) {
  if (!GEP->hasAllConstantIndices())
    return false;
  Ptr = GEP->getPointerOperand();
}    
```


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D143641