Implement computeKnownBits for min/max nodes

llvm-svn: 239378

1 files changed, 22 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 804c0805c34..cf51e756d84 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2432,6 +2432,19 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
     KnownOne = KnownOne.trunc(BitWidth);
     break;
   }
+  case ISD::SMIN:
+  case ISD::SMAX:
+  case ISD::UMIN:
+  case ISD::UMAX: {
+    APInt Op0Zero, Op0One;
+    APInt Op1Zero, Op1One;
+    computeKnownBits(Op.getOperand(0), Op0Zero, Op0One, Depth);
+    computeKnownBits(Op.getOperand(1), Op1Zero, Op1One, Depth);
+
+    KnownZero = Op0Zero & Op1Zero;
+    KnownOne = Op0One & Op1One;
+    break;
+  }
   case ISD::FrameIndex:
   case ISD::TargetFrameIndex:
     if (unsigned Align = InferPtrAlignment(Op)) {
@@ -2535,7 +2548,15 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, unsigned Depth) const{
     if (Tmp == 1) return 1;  // Early out.
     Tmp2 = ComputeNumSignBits(Op.getOperand(2), Depth+1);
     return std::min(Tmp, Tmp2);
-
+  case ISD::SMIN:
+  case ISD::SMAX:
+  case ISD::UMIN:
+  case ISD::UMAX:
+    Tmp = ComputeNumSignBits(Op.getOperand(0), Depth + 1);
+    if (Tmp == 1)
+      return 1;  // Early out.
+    Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth + 1);
+    return std::min(Tmp, Tmp2);
   case ISD::SADDO:
   case ISD::UADDO:
   case ISD::SSUBO: