[DAGCombiner] ISD::SDIV/UDIV/SREM/UREM - use general SelectionDAG::FoldConstantArithmetic

This handles all the constant splat / opaque testing for us.

Author: RKSimon

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -3741,13 +3741,14 @@ SDValue DAGCombiner::visitSDIV(SDNode *N) {
   SDLoc DL(N);
 
   // fold (sdiv c1, c2) -> c1/c2
-  ConstantSDNode *N0C = isConstOrConstSplat(N0);
   ConstantSDNode *N1C = isConstOrConstSplat(N1);
-  if (N0C && N1C && !N0C->isOpaque() && !N1C->isOpaque())
-    return DAG.FoldConstantArithmetic(ISD::SDIV, DL, VT, N0C, N1C);
+  if (SDValue C = DAG.FoldConstantArithmetic(ISD::SDIV, DL, VT, {N0, N1}))
+    return C;
+
   // fold (sdiv X, -1) -> 0-X
   if (N1C && N1C->isAllOnesValue())
     return DAG.getNode(ISD::SUB, DL, VT, DAG.getConstant(0, DL, VT), N0);
+
   // fold (sdiv X, MIN_SIGNED) -> select(X == MIN_SIGNED, 1, 0)
   if (N1C && N1C->getAPIntValue().isMinSignedValue())
     return DAG.getSelect(DL, VT, DAG.getSetCC(DL, CCVT, N0, N1, ISD::SETEQ),
@@ -3885,12 +3886,10 @@ SDValue DAGCombiner::visitUDIV(SDNode *N) {
   SDLoc DL(N);
 
   // fold (udiv c1, c2) -> c1/c2
-  ConstantSDNode *N0C = isConstOrConstSplat(N0);
   ConstantSDNode *N1C = isConstOrConstSplat(N1);
-  if (N0C && N1C)
-    if (SDValue Folded = DAG.FoldConstantArithmetic(ISD::UDIV, DL, VT,
-                                                    N0C, N1C))
-      return Folded;
+  if (SDValue C = DAG.FoldConstantArithmetic(ISD::UDIV, DL, VT, {N0, N1}))
+    return C;
+
   // fold (udiv X, -1) -> select(X == -1, 1, 0)
   if (N1C && N1C->getAPIntValue().isAllOnesValue())
     return DAG.getSelect(DL, VT, DAG.getSetCC(DL, CCVT, N0, N1, ISD::SETEQ),
@@ -3983,11 +3982,10 @@ SDValue DAGCombiner::visitREM(SDNode *N) {
   SDLoc DL(N);
 
   // fold (rem c1, c2) -> c1%c2
-  ConstantSDNode *N0C = isConstOrConstSplat(N0);
   ConstantSDNode *N1C = isConstOrConstSplat(N1);
-  if (N0C && N1C)
-    if (SDValue Folded = DAG.FoldConstantArithmetic(Opcode, DL, VT, N0C, N1C))
-      return Folded;
+  if (SDValue C = DAG.FoldConstantArithmetic(Opcode, DL, VT, {N0, N1}))
+    return C;
+
   // fold (urem X, -1) -> select(X == -1, 0, x)
   if (!isSigned && N1C && N1C->getAPIntValue().isAllOnesValue())
     return DAG.getSelect(DL, VT, DAG.getSetCC(DL, CCVT, N0, N1, ISD::SETEQ),