[llvm] [ABI] Add DefaultTargetInfo for default argument/return classification (PR #225009)

[via llvm-commits]

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@@ -71,6 +71,45 @@ const Type *TargetInfo::useFirstFieldIfTransparentUnion(const Type *Ty) const {
   return Ty;
 }
 
+ArgInfo TargetInfo::classifyDefaultArgumentType(const Type *Ty) const {
+  Ty = useFirstFieldIfTransparentUnion(Ty);
+
+  if (isAggregateTypeForABI(Ty)) {
+    // A record that must stay in memory keeps ByVal, everything else indirect.
+    if (RecordArgABI RAA = getRecordArgABI(Ty))
+      return getNaturalAlignIndirect(Ty, /*ByVal=*/RAA == RAA_DirectInMemory);
+    return getNaturalAlignIndirect(Ty);
+  }
+
+  if (const auto *IT = dyn_cast<IntegerType>(Ty)) {
+    // A _BitInt wider than 128 bits does not fit in registers.
+    if (IT->isBitInt() && IT->getSizeInBits().getFixedValue() > 128)
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skc7 wrote:

Added `hasInt128Type()` and `getLongLongWidth()` hooks plus a `getBitIntRegThreshold()` helper mirroring classic, and used it in both `DefaultTargetInfo` classifiers.

https://github.com/llvm/llvm-project/pull/225009