As comments said, for negative value, the arithmetic 
over-shift-right should return -1. So here it should be signed-extended,
when bitwidth larger than 64.

test case: llvm/test/ExecutionEngine/2008-06-05-APInt-OverAShr.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51999 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp
index ef35e1c..e13011f 100644
--- a/lib/Support/APInt.cpp
+++ b/lib/Support/APInt.cpp
@@ -1113,7 +1113,7 @@
   // issues in the algorithm below.
   if (shiftAmt == BitWidth) {
     if (isNegative())
-      return APInt(BitWidth, -1ULL);
+      return APInt(BitWidth, -1ULL, true);
     else
       return APInt(BitWidth, 0);
   }