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

[Shilei Tian via llvm-commits]

================
@@ -12699,46 +12673,59 @@ struct AAAllocationInfoImpl : public AAAllocationInfo {
     const DataLayout &DL = A.getDataLayout();
     const auto AllocationSize = findInitialAllocationSize(I, DL);
 
-    // If allocation size is nullopt, we give up.
+    // If allocation size is nullopt, we give up
     if (!AllocationSize)
       return indicatePessimisticFixpoint();
 
-    // For zero sized allocations, we give up.
+    // For zero sized allocations, we give up
     // Since we can't reduce further
     if (*AllocationSize == 0)
       return indicatePessimisticFixpoint();
 
-    int64_t BinSize = PI->numOffsetBins();
+    int64_t NumBins = PI->numOffsetBins();
 
-    // TODO: implement for multiple bins
-    if (BinSize > 1)
-      return indicatePessimisticFixpoint();
-
-    if (BinSize == 0) {
+    if (NumBins == 0) {
       auto NewAllocationSize = std::optional<TypeSize>(TypeSize(0, false));
       if (!changeAllocationSize(NewAllocationSize))
         return ChangeStatus::UNCHANGED;
       return ChangeStatus::CHANGED;
     }
 
-    // TODO: refactor this to be part of multiple bin case
-    const auto &It = PI->begin();
+    // For each access bin
+    // Compute its new start Offset and store the results in a new map
+    // (NewOffsetBins)
+    unsigned long PrevBinEndOffset = 0;
+    bool ChangedOffsets = false;
 
-    // TODO: handle if Offset is not zero
-    if (It->first.Offset != 0)
-      return indicatePessimisticFixpoint();
+    for (AAPointerInfo::OffsetBinsTy::const_iterator It = PI->begin();
+         It != PI->end(); It++) {
+      const AA::RangeTy &OldRange = It->getFirst();
 
-    uint64_t SizeOfBin = It->first.Offset + It->first.Size;
+      // If any range has an unknown offset or size, we should leave the
+      // allocation unmodified
+      if (OldRange.offsetOrSizeAreUnknown()) {
+        return indicatePessimisticFixpoint();
+      }
----------------
shiltian wrote:

```suggestion
      if (OldRange.offsetOrSizeAreUnknown())
        return indicatePessimisticFixpoint();
```

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