Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp	(revision 61100)
+++ lib/Target/X86/X86ISelLowering.cpp	(working copy)
@@ -4639,22 +4639,43 @@
     Tmp3 = DAG.getNode(isSRA ? ISD::SRA : ISD::SRL, VT, ShOpHi, ShAmt);
   }
 
-  SDValue AndNode = DAG.getNode(ISD::AND, MVT::i8, ShAmt,
+  APInt KnownZero, KnownOne;
+  DAG.ComputeMaskedBits(ShAmt, APInt(8, VTBits), KnownZero, KnownOne, 0);
+
+  SDValue Hi, Lo;
+  if (KnownZero == VTBits) {
+    if (Op.getOpcode() == ISD::SHL_PARTS) {
+      Lo = Tmp3;
+      Hi = Tmp2;
+    } else {
+      Lo = Tmp2;
+      Hi = Tmp3;
+    }
+  } else if (KnownOne == VTBits) {
+    if (Op.getOpcode() == ISD::SHL_PARTS) {
+      Lo = Tmp1;
+      Hi = Tmp3;
+    } else {
+      Lo = Tmp3;
+      Hi = Tmp1;
+    }
+  } else {
+    SDValue AndNode = DAG.getNode(ISD::AND, MVT::i8, ShAmt,
                                   DAG.getConstant(VTBits, MVT::i8));
-  SDValue Cond = DAG.getNode(X86ISD::CMP, VT,
+    SDValue Cond = DAG.getNode(X86ISD::CMP, VT,
                                AndNode, DAG.getConstant(0, MVT::i8));
 
-  SDValue Hi, Lo;
-  SDValue CC = DAG.getConstant(X86::COND_NE, MVT::i8);
-  SDValue Ops0[4] = { Tmp2, Tmp3, CC, Cond };
-  SDValue Ops1[4] = { Tmp3, Tmp1, CC, Cond };
+    SDValue CC = DAG.getConstant(X86::COND_NE, MVT::i8);
+    SDValue Ops0[4] = { Tmp2, Tmp3, CC, Cond };
+    SDValue Ops1[4] = { Tmp3, Tmp1, CC, Cond };
 
-  if (Op.getOpcode() == ISD::SHL_PARTS) {
-    Hi = DAG.getNode(X86ISD::CMOV, VT, Ops0, 4);
-    Lo = DAG.getNode(X86ISD::CMOV, VT, Ops1, 4);
-  } else {
-    Lo = DAG.getNode(X86ISD::CMOV, VT, Ops0, 4);
-    Hi = DAG.getNode(X86ISD::CMOV, VT, Ops1, 4);
+    if (Op.getOpcode() == ISD::SHL_PARTS) {
+      Hi = DAG.getNode(X86ISD::CMOV, VT, Ops0, 4);
+      Lo = DAG.getNode(X86ISD::CMOV, VT, Ops1, 4);
+    } else {
+      Lo = DAG.getNode(X86ISD::CMOV, VT, Ops0, 4);
+      Hi = DAG.getNode(X86ISD::CMOV, VT, Ops1, 4);
+    }
   }
 
   SDValue Ops[2] = { Lo, Hi };
@@ -7291,7 +7312,15 @@
     KnownZero |= APInt::getHighBitsSet(Mask.getBitWidth(),
                                        Mask.getBitWidth() - 1);
     break;
+  case X86ISD::CMOV: {
+    APInt KnownZero2, KnownOne2;
+    DAG.ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
+    DAG.ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
+    KnownZero &= KnownZero2;
+    KnownOne &= KnownOne2;
+    break;
   }
+  }
 }
 
 /// isGAPlusOffset - Returns true (and the GlobalValue and the offset) if the