[DAGCombiner] Enable add saturation constant folding

llvm-svn: 351060

2 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 580a668100b..9a40774cff8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2198,8 +2198,9 @@ SDValue DAGCombiner::visitADDSAT(SDNode *N) {
     // canonicalize constant to RHS
     if (!DAG.isConstantIntBuildVectorOrConstantInt(N1))
       return DAG.getNode(Opcode, DL, VT, N1, N0);
-
-    // TODO Constant Folding
+    // fold (add_sat c1, c2) -> c3
+    return DAG.FoldConstantArithmetic(Opcode, DL, VT, N0.getNode(),
+                                      N1.getNode());
   }
 
   // fold (add_sat x, 0) -> x
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 23a7b3ece82..a0ee80c0dcd 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4488,6 +4488,8 @@ static std::pair<APInt, bool> FoldValue(unsigned Opcode, const APInt &C1,
   case ISD::SMAX: return std::make_pair(C1.sge(C2) ? C1 : C2, true);
   case ISD::UMIN: return std::make_pair(C1.ule(C2) ? C1 : C2, true);
   case ISD::UMAX: return std::make_pair(C1.uge(C2) ? C1 : C2, true);
+  case ISD::SADDSAT: return std::make_pair(C1.sadd_sat(C2), true);
+  case ISD::UADDSAT: return std::make_pair(C1.uadd_sat(C2), true);
   case ISD::UDIV:
     if (!C2.getBoolValue())
       break;