[llvm] [ConstraintElim] Use constraints from bounded memory accesses (PR #155253)

[Nikita Popov via llvm-commits]

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@@ -1127,6 +1164,38 @@ void State::addInfoFor(BasicBlock &BB) {
       continue;
     }
 
+    auto AddFactFromMemoryAccess = [&](Value *Ptr, Type *AccessType) {
+      auto *GEP = dyn_cast<GetElementPtrInst>(Ptr);
+      if (!GEP)
+        return;
+      TypeSize AccessSize = DL.getTypeStoreSize(AccessType);
+      if (!AccessSize.isFixed())
+        return;
+      if (GuaranteedToExecute) {
+        CmpPredicate Pred;
+        Value *A, *B;
+        if (getConstraintFromMemoryAccess(*GEP, AccessSize.getFixedValue(),
+                                          Pred, A, B, DL, TLI)) {
+          // The memory access is guaranteed to execute when BB is entered,
+          // hence the constraint holds on entry to BB.
+          WorkList.emplace_back(FactOrCheck::getConditionFact(
+              DT.getNode(I.getParent()), Pred, A, B));
+        }
+      } else {
+        WorkList.emplace_back(
+            FactOrCheck::getInstFact(DT.getNode(I.getParent()), &I));
+      }
+    };
+
+    if (auto *LI = dyn_cast<LoadInst>(&I)) {
+      if (LI->isSimple())
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nikic wrote:

Why the isSimple limitation?

https://github.com/llvm/llvm-project/pull/155253