[DAG] visitADDLike - convert (A-B)+(C-D) --> (A+C)-(B+D) fold to sd_match. NFC.

Author: RKSimon

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -2743,7 +2743,7 @@ SDValue DAGCombiner::visitADDLike(SDNode *N) {
       return SD;
   }
 
-  SDValue A, B, C;
+  SDValue A, B, C, D;
 
   // fold ((0-A) + B) -> B-A
   if (sd_match(N0, m_Neg(m_Value(A))))
@@ -2783,18 +2783,12 @@ SDValue DAGCombiner::visitADDLike(SDNode *N) {
     return DAG.getNode(N1.getOpcode(), DL, VT, B, C);
 
   // fold (A-B)+(C-D) to (A+C)-(B+D) when A or C is constant
-  if (N0.getOpcode() == ISD::SUB && N1.getOpcode() == ISD::SUB &&
-      N0->hasOneUse() && N1->hasOneUse()) {
-    SDValue N00 = N0.getOperand(0);
-    SDValue N01 = N0.getOperand(1);
-    SDValue N10 = N1.getOperand(0);
-    SDValue N11 = N1.getOperand(1);
-
-    if (isConstantOrConstantVector(N00) || isConstantOrConstantVector(N10))
-      return DAG.getNode(ISD::SUB, DL, VT,
-                         DAG.getNode(ISD::ADD, SDLoc(N0), VT, N00, N10),
-                         DAG.getNode(ISD::ADD, SDLoc(N1), VT, N01, N11));
-  }
+  if (sd_match(N0, m_OneUse(m_Sub(m_Value(A), m_Value(B)))) &&
+      sd_match(N1, m_OneUse(m_Sub(m_Value(C), m_Value(D)))) &&
+      (isConstantOrConstantVector(A) || isConstantOrConstantVector(C)))
+    return DAG.getNode(ISD::SUB, DL, VT,
+                       DAG.getNode(ISD::ADD, SDLoc(N0), VT, A, C),
+                       DAG.getNode(ISD::ADD, SDLoc(N1), VT, B, D));
 
   // fold (add (umax X, C), -C) --> (usubsat X, C)
   if (N0.getOpcode() == ISD::UMAX && hasOperation(ISD::USUBSAT, VT)) {