[llvm] [Attributor] New attribute to identify what byte ranges are alive for an allocation (PR #66148)

[Johannes Doerfert via llvm-commits]

================
@@ -12658,6 +12669,268 @@ struct AAAddressSpaceCallSiteArgument final : AAAddressSpaceImpl {
 };
 } // namespace
 
+/// ----------- Allocation Info ----------
+namespace {
+struct AAAllocationInfoImpl : public AAAllocationInfo {
+  AAAllocationInfoImpl(const IRPosition &IRP, Attributor &A)
+      : AAAllocationInfo(IRP, A) {}
+
+  std::optional<TypeSize> getAllocatedSize() const override {
+    assert(isValidState() && "the AA is invalid");
+    return AssumedAllocatedSize;
+  }
+
+  bool isaMallocInst(Instruction *I) {
+    CallInst *Call = dyn_cast<CallInst>(I);
+    auto CallName = Call->getCalledFunction()->getName();
+    if (CallName.str() == "malloc")
+      return true;
+
+    return false;
+  };
+
+  ChangeStatus updateImpl(Attributor &A) override {
+
+    Instruction *I = getIRPosition().getCtxI();
+
+    const IRPosition &IRP = getIRPosition();
+
+    if (!(isa<AllocaInst>(I) || isaMallocInst(I)))
+      return llvm::IntegerStateBase<bool, true,
+                                    false>::indicatePessimisticFixpoint();
+
+    const AAPointerInfo *PI =
+        A.getOrCreateAAFor<AAPointerInfo>(IRP, *this, DepClassTy::REQUIRED);
+
+    if (!PI)
+      return indicatePessimisticFixpoint();
+
+    if (!PI->getState().isValidState())
+      return indicatePessimisticFixpoint();
+
+    int64_t BinSize = PI->numOffsetBins();
+
+    // TODO: Handle for more than one Bin
+    if (BinSize > 1)
+      return indicatePessimisticFixpoint();
+
+    const auto &It = PI->begin();
+
+    if (BinSize == 0)
+      return indicatePessimisticFixpoint();
+
+    if (It->first.Offset != 0)
+      return indicatePessimisticFixpoint();
+
+    uint64_t OffsetEnd = It->first.Offset + It->first.Size;
+    const DataLayout &DL = A.getDataLayout();
+
+    switch (I->getOpcode()) {
+    case Instruction::Alloca: {
+      AllocaInst *AI = dyn_cast<AllocaInst>(getIRPosition().getCtxI());
----------------
jdoerfert wrote:

2 lines above you use I, here you use getIRPosition() (which you assigned to IRP in the beginning) and then you use getCtxI() (which is I).
Also, you just checked the opcode, no need to *dyn_*cast, no need to check for !AI.


https://github.com/llvm/llvm-project/pull/66148