Let each target specific isel provide routine to check if a chain producing node is foldable by another.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29335 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/SelectionDAGISel.h

@@ -62,6 +62,10 @@ public:
                                             SelectionDAG &DAG) {
     return true;
   }
+
+  /// IsFoldableBy - Returns true if the specific operand node N of U can be
+  /// folded during instruction selection?
+  virtual bool IsFoldableBy(SDNode *N, SDNode *U) { return true; }
   
   /// CreateTargetHazardRecognizer - Return a newly allocated hazard recognizer
   /// to use for this target when scheduling the DAG.
@@ -111,7 +115,7 @@ protected:
   /// by tblgen.  Others should not call it.
   void SelectInlineAsmMemoryOperands(std::vector<SDOperand> &Ops,
                                      SelectionDAG &DAG);
-  
+
 private:
   SDOperand CopyValueToVirtualRegister(SelectionDAGLowering &SDL,
                                        Value *V, unsigned Reg);

utils/TableGen/DAGISelEmitter.cpp

@@ -2280,14 +2280,8 @@ public:
               PInfo.hasProperty(SDNodeInfo::SDNPHasChain) ||
               PInfo.hasProperty(SDNodeInfo::SDNPInFlag) ||
               PInfo.hasProperty(SDNodeInfo::SDNPOptInFlag))
-            if (PInfo.getNumOperands() > 1) {
-              emitCheck("!isNonImmUse(" + ParentName + ".Val, " + RootName +
-                        ".Val)");
-            } else {
-              emitCheck("(" + ParentName + ".getNumOperands() == 1 || !" +
-                        "isNonImmUse(" + ParentName + ".Val, " + RootName +
-                        ".Val))");
-            }
+            emitCheck("IsFoldableBy(" + RootName + ".Val, " + ParentName +
+                      ".Val)");
         }
       }