[clang] [llvm] [LLVMAABI][AARCH64] Handle homogeneous aggregate return types (PR #218799)

[Eli Friedman via cfe-commits]

================
@@ -82,3 +89,123 @@ bool TargetInfo::maybeCommonClassifyReturnType(FunctionInfo &FI) const {
 
   return false;
 }
+
+namespace {
+
+bool isEmptyRecordForHA(const Type *Ty) {
+  const auto *RT = dyn_cast<RecordType>(Ty);
+  return RT && RT->isEmpty();
+}
+
+/// Storage-container width mirroring Clang's ASTContext::getTypeSize for the
+/// types that matter to homogeneous-aggregate detection.
+uint64_t getHATypeSizeInBits(const Type *Ty) {
+  if (const auto *VT = dyn_cast<VectorType>(Ty)) {
+    uint64_t EltWidth = VT->getElementType()->getSizeInBits().getFixedValue();
+    uint64_t Width = std::max<uint64_t>(
+        8, EltWidth * VT->getNumElements().getKnownMinValue());
+    if (Width & (Width - 1))
+      Width = alignTo(Width, bit_ceil(Width));
+    return Width;
+  }
+  return Ty->getSizeInBits().getFixedValue();
+}
+
+} // namespace
+
+bool TargetInfo::isHomogeneousAggregate(const Type *Ty, const Type *&Base,
+                                        uint64_t &Members) const {
----------------
efriedma-quic wrote:

Matrix types are a recent clang extension, and not part of Arm's documented ABI, so probably nobody really looked that closely at how they behave.

https://github.com/llvm/llvm-project/pull/218799