[llvm] [Attributor] Change allocation size and load/store offsets using AAPointerInfo for Alloca instructions (PR #72029)

[Shilei Tian via llvm-commits]

================
@@ -12752,39 +12734,315 @@ struct AAAllocationInfoImpl : public AAAllocationInfo {
     assert(isValidState() &&
            "Manifest should only be called if the state is valid.");
 
-    Instruction *I = getIRPosition().getCtxI();
+    bool Changed = false;
+    const IRPosition &IRP = getIRPosition();
+    Instruction *I = IRP.getCtxI();
+
+    // check if simplified values exist
+    if (checkIfSimplifiedValuesExists(A, I))
+      return ChangeStatus::UNCHANGED;
+
+    if (getAllocatedSize() == HasNoAllocationSize)
+      return ChangeStatus::UNCHANGED;
+
+    const AAPointerInfo *PI =
+        A.getOrCreateAAFor<AAPointerInfo>(IRP, *this, DepClassTy::REQUIRED);
+
+    if (!PI)
+      return ChangeStatus::UNCHANGED;
+
+    if (!PI->getState().isValidState())
+      return ChangeStatus::UNCHANGED;
+
+    // Store a map where each instruction maps to a set of bins accessed by that
+    // instruction
+    DenseMap<Instruction *, DenseMap<AA::RangeTy, AA::RangeTy>>
+        AccessedInstructionsToBinsMap;
+
+    auto AddBins =
+        [](DenseMap<Instruction *, DenseMap<AA::RangeTy, AA::RangeTy>> &Map,
+           Instruction *LocalInst, const AA::RangeTy &OldRange,
+           const AA::RangeTy &NewRange) {
+          DenseMap<AA::RangeTy, AA::RangeTy> &NewBinsForInstruction =
+              Map.getOrInsertDefault(LocalInst);
+
+          NewBinsForInstruction.insert(std::make_pair(OldRange, NewRange));
+        };
+
+    const auto &NewOffsetsMap = getNewOffsets();
+    const auto &OffsetInfoMap = PI->getOffsetInfoMap();
+
+    // Map access causing instructions to tuple of (Old, New) bins.
+    // The access causing instruction contains the pointer operand
+    // which comes from the allocation
+    // We may want to backtrack that pointer operand, there are 2 cases that may
+    // arise
+
+    // A) A GEP exists that calculates the pointer operand from the original
+    // allocation instruction: I
+
+    // B) A GEP does not exists
+    // in which case we need to insert a GEP just before the access causing
+    // instruction with the shift value from the original offset.
----------------
shiltian wrote:

```suggestion
    // Map access causing instructions to tuple of (Old, New) bins.
    // The access causing instruction contains the pointer operand
    // which comes from the allocation
    // We may want to backtrack that pointer operand, there are 2 cases that may
    // arise:
    // A) A GEP exists that calculates the pointer operand from the original
    // allocation instruction: I
    // B) A GEP does not exists
    // in which case we need to insert a GEP just before the access causing
    // instruction with the shift value from the original offset.
```

https://github.com/llvm/llvm-project/pull/72029