ARM byval support. Will be enabled by another patch to the FE. <rdar://problem/7662569>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129858 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/CallingConvLower.h

@@ -141,6 +141,8 @@ typedef bool CCCustomFn(unsigned &ValNo, MVT &ValVT,
                         MVT &LocVT, CCValAssign::LocInfo &LocInfo,
                         ISD::ArgFlagsTy &ArgFlags, CCState &State);
 
+typedef enum { Invalid, Prologue, Call } ParmContext;
+
 /// CCState - This class holds information needed while lowering arguments and
 /// return values.  It captures which registers are already assigned and which
 /// stack slots are used.  It provides accessors to allocate these values.
@@ -154,6 +156,9 @@ class CCState {
 
   unsigned StackOffset;
   SmallVector<uint32_t, 16> UsedRegs;
+  unsigned FirstByValReg;
+  bool FirstByValRegValid;
+  ParmContext CallOrPrologue;
 public:
   CCState(CallingConv::ID CC, bool isVarArg, const TargetMachine &TM,
           SmallVector<CCValAssign, 16> &locs, LLVMContext &C);
@@ -288,6 +293,16 @@ public:
                    MVT LocVT, CCValAssign::LocInfo LocInfo,
                    int MinSize, int MinAlign, ISD::ArgFlagsTy ArgFlags);
 
+  // First GPR that carries part of a byval aggregate that's split
+  // between registers and memory.
+  unsigned getFirstByValReg() { return FirstByValRegValid ? FirstByValReg : 0; }
+  void setFirstByValReg(unsigned r) { FirstByValReg = r; FirstByValRegValid = true; }
+  void clearFirstByValReg() { FirstByValReg = 0; FirstByValRegValid = false; }
+  bool isFirstByValRegValid() { return FirstByValRegValid; }
+
+  ParmContext getCallOrPrologue() { return CallOrPrologue; }
+  void setCallOrPrologue(ParmContext pc) { CallOrPrologue = pc; }
+
 private:
   /// MarkAllocated - Mark a register and all of its aliases as allocated.
   void MarkAllocated(unsigned Reg);

include/llvm/Target/TargetLowering.h

@@ -1253,7 +1253,7 @@ public:
   }
 
   /// HandleByVal - Target-specific cleanup for formal ByVal parameters.
-  virtual void HandleByVal(CCState *) const {}
+  virtual void HandleByVal(CCState *, unsigned &) const {}
 
   /// CanLowerReturn - This hook should be implemented to check whether the
   /// return values described by the Outs array can fit into the return