Add code to check at SelectionDAGISel::LowerArguments time to see if return values can be lowered to registers. Coming soon, code to perform sret-demotion if return values cannot be lowered to registers

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86324 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 19 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/CallingConvLower.h b/include/llvm/CodeGen/CallingConvLower.h
index 5e730fc12c..45a2757d37 100644
--- a/include/llvm/CodeGen/CallingConvLower.h
+++ b/include/llvm/CodeGen/CallingConvLower.h
@@ -183,6 +183,13 @@ public:
   void AnalyzeReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
                      CCAssignFn Fn);
 
+  /// CheckReturn - Analyze the return values of a function, returning
+  /// true if the return can be performed without sret-demotion, and
+  /// false otherwise.
+  bool CheckReturn(const SmallVectorImpl<EVT> &OutTys,
+                   const SmallVectorImpl<ISD::ArgFlagsTy> &ArgsFlags,
+                   CCAssignFn Fn);
+
   /// AnalyzeCallOperands - Analyze the outgoing arguments to a call,
   /// incorporating info about the passed values into this state.
   void AnalyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index 8bc39d0b2c..1526a0de0c 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -1167,6 +1167,18 @@ public:
     return SDValue();    // this is here to silence compiler errors
   }
 
+  /// CanLowerReturn - This hook should be implemented to check whether the
+  /// return values described by the Outs array can fit into the return
+  /// registers.  If false is returned, an sret-demotion is performed.
+  ///
+  virtual bool CanLowerReturn(CallingConv::ID CallConv, bool isVarArg,
+               const SmallVectorImpl<EVT> &OutTys,
+               const SmallVectorImpl<ISD::ArgFlagsTy> &ArgsFlags,
+               SelectionDAG &DAG)
+  {
+    // Return true by default to get preexisting behavior.
+    return true;
+  }
   /// LowerReturn - This hook must be implemented to lower outgoing
   /// return values, described by the Outs array, into the specified
   /// DAG. The implementation should return the resulting token chain