revert part of the last change, should fix regressions

llvm-svn: 23241
diff --git a/llvm/lib/Target/Alpha/AlphaISelPattern.cpp b/llvm/lib/Target/Alpha/AlphaISelPattern.cpp
index 2af3e9b..cc0392b 100644
--- a/llvm/lib/Target/Alpha/AlphaISelPattern.cpp
+++ b/llvm/lib/Target/Alpha/AlphaISelPattern.cpp
@@ -1733,6 +1733,11 @@
       BuildMI(BB, Opc, 1, Result).addReg(Alpha::F31).addReg(Tmp2);
       return Result;
     }
+
+  case ISD::AssertSext:
+  case ISD::AssertZext:
+    return SelectExpr(N.getOperand(0));
+
   }
 
   return 0;