Switch to LLVM support function abs64 to keep VS2008 happy.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178141 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/Hexagon/HexagonHardwareLoops.cpp b/lib/Target/Hexagon/HexagonHardwareLoops.cpp
index 62aed13..a46b8d3 100644
--- a/lib/Target/Hexagon/HexagonHardwareLoops.cpp
+++ b/lib/Target/Hexagon/HexagonHardwareLoops.cpp
@@ -701,7 +701,7 @@
 
   // If the induction variable bump is not a power of 2, quit.
   // Othwerise we'd need a general integer division.
-  if (!isPowerOf2_64(abs(IVBump)))
+  if (!isPowerOf2_64(abs64(IVBump)))
     return 0;
 
   MachineBasicBlock *PH = Loop->getLoopPreheader();