[MSP430] Add SRet support to MSP430 target

This patch adds support for struct return values to the MSP430
target backend. It also reverses the order of argument and return
registers in the calling convention to bring it into closer
alignment with the published EABI from TI.

Patch by Andrew Wygle (awygle).

Differential Revision: https://reviews.llvm.org/D29069

llvm-svn: 296807

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/Target/MSP430/MSP430MachineFunctionInfo.h b/llvm/lib/Target/MSP430/MSP430MachineFunctionInfo.h
index 2d937318c7e..fcaa8a1d6c7 100644
--- a/llvm/lib/Target/MSP430/MSP430MachineFunctionInfo.h
+++ b/llvm/lib/Target/MSP430/MSP430MachineFunctionInfo.h
@@ -33,15 +33,23 @@ class MSP430MachineFunctionInfo : public MachineFunctionInfo {
   /// VarArgsFrameIndex - FrameIndex for start of varargs area.
   int VarArgsFrameIndex;
 
+  /// SRetReturnReg - Some subtargets require that sret lowering includes
+  /// returning the value of the returned struct in a register. This field
+  /// holds the virtual register into which the sret argument is passed.
+  unsigned SRetReturnReg;
+
 public:
   MSP430MachineFunctionInfo() : CalleeSavedFrameSize(0) {}
 
   explicit MSP430MachineFunctionInfo(MachineFunction &MF)
-    : CalleeSavedFrameSize(0), ReturnAddrIndex(0) {}
+    : CalleeSavedFrameSize(0), ReturnAddrIndex(0), SRetReturnReg(0) {}
 
   unsigned getCalleeSavedFrameSize() const { return CalleeSavedFrameSize; }
   void setCalleeSavedFrameSize(unsigned bytes) { CalleeSavedFrameSize = bytes; }
 
+  unsigned getSRetReturnReg() const { return SRetReturnReg; }
+  void setSRetReturnReg(unsigned Reg) { SRetReturnReg = Reg; }
+
   int getRAIndex() const { return ReturnAddrIndex; }
   void setRAIndex(int Index) { ReturnAddrIndex = Index; }