[llvm] [AsmPrinter] Fix handling in emitGlobalConstantImpl for AIX (PR #116255)

[Hubert Tong via llvm-commits]

================
@@ -3858,7 +3860,29 @@ static void emitGlobalConstantImpl(const DataLayout &DL, const Constant *CV,
   if (!BaseCV && CV->hasOneUse())
     BaseCV = dyn_cast<Constant>(CV->user_back());
 
-  if (isa<ConstantAggregateZero>(CV) || isa<UndefValue>(CV))
+  if (isa<ConstantAggregateZero>(CV)) {
+    StructType *structType;
+    if (AliasList && (structType = llvm::dyn_cast<StructType>(CV->getType()))) {
+      // Handle cases of aliases to direct struct elements
+      const StructLayout *Layout = DL.getStructLayout(structType);
+      uint64_t SizeSoFar = 0;
+      for (unsigned int i = 0, n = structType->getNumElements(); i < n - 1;
+           ++i) {
+        emitGlobalAliasInline(AP, Offset + SizeSoFar, AliasList);
+        uint64_t GapToNext = Layout->getElementOffset(i + 1) - SizeSoFar;
+        AP.OutStreamer->emitZeros(GapToNext);
+        SizeSoFar += GapToNext;
+      }
+      emitGlobalAliasInline(AP, Offset + SizeSoFar, AliasList);
----------------
hubert-reinterpretcast wrote:

The alias-at-offset-zero-from-`Offset` case is already handled in the status quo.
```suggestion
        uint64_t GapToNext = Layout->getElementOffset(i + 1) - SizeSoFar;
        AP.OutStreamer->emitZeros(GapToNext);
        SizeSoFar += GapToNext;
        emitGlobalAliasInline(AP, Offset + SizeSoFar, AliasList);
      }
```

https://github.com/llvm/llvm-project/pull/116255