1 files changed, 15 insertions, 0 deletions
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.h b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
index 86f1d972c9d..882ed19480b 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -215,6 +215,21 @@ enum NodeType : unsigned {
 
 } // end namespace AArch64ISD
 
+namespace {
+
+// Any instruction that defines a 32-bit result zeros out the high half of the
+// register. Truncate can be lowered to EXTRACT_SUBREG. CopyFromReg may
+// be copying from a truncate. But any other 32-bit operation will zero-extend
+// up to 64 bits.
+// FIXME: X86 also checks for CMOV here. Do we need something similar?
+static inline bool isDef32(const SDNode &N) {
+  unsigned Opc = N.getOpcode();
+  return Opc != ISD::TRUNCATE && Opc != TargetOpcode::EXTRACT_SUBREG &&
+         Opc != ISD::CopyFromReg;
+}
+
+} // end anonymous namespace
+
 class AArch64Subtarget;
 class AArch64TargetMachine;