Change AArch64 i128 returns to use [2 x i64] when possible.

Something like { void*, void * } would be passed to a function as a [2 x i64], but returned as an i128.  This patch unifies the 2 behaviours so that we also return it as a [2 x i64].

This is better for the quality of the IR, and the size of the final LLVM binary as we tend to want to insert/extract values from these types and do so with the insert/extract instructions is less IR than shifting, truncating, and or'ing values.

Reviewed by Tim Northover.

llvm-svn: 235231

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 05529656d18..23d304731f1 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -4044,7 +4044,15 @@ ABIArgInfo AArch64ABIInfo::classifyReturnType(QualType RetTy) const {
   // Aggregates <= 16 bytes are returned directly in registers or on the stack.
   uint64_t Size = getContext().getTypeSize(RetTy);
   if (Size <= 128) {
+    unsigned Alignment = getContext().getTypeAlign(RetTy);
     Size = 64 * ((Size + 63) / 64); // round up to multiple of 8 bytes
+
+    // We use a pair of i64 for 16-byte aggregate with 8-byte alignment.
+    // For aggregates with 16-byte alignment, we use i128.
+    if (Alignment < 128 && Size == 128) {
+      llvm::Type *BaseTy = llvm::Type::getInt64Ty(getVMContext());
+      return ABIArgInfo::getDirect(llvm::ArrayType::get(BaseTy, Size / 64));
+    }
     return ABIArgInfo::getDirect(llvm::IntegerType::get(getVMContext(), Size));
   }