Now that PR633 is implemented, the CBE can know to emit _setjmp/_longjmp
when available.  This speeds up hexxagon from 18.61s to 16.61s with the CBE on
PPC Mac OS (for reference, LLC is 15.48s and GCC is 23.35s).

llvm-svn: 28697
diff --git a/llvm/lib/Target/CBackend/Writer.cpp b/llvm/lib/Target/CBackend/Writer.cpp
index 36336b3..692232b 100644
--- a/llvm/lib/Target/CBackend/Writer.cpp
+++ b/llvm/lib/Target/CBackend/Writer.cpp
@@ -1779,11 +1779,17 @@
         Out << ')';
         return;
       case Intrinsic::setjmp:
+#if defined(HAVE__SETJMP) && defined(HAVE__LONGJMP)
+        Out << "_";  // Use _setjmp on systems that support it!
+#endif
         Out << "setjmp(*(jmp_buf*)";
         writeOperand(I.getOperand(1));
         Out << ')';
         return;
       case Intrinsic::longjmp:
+#if defined(HAVE__SETJMP) && defined(HAVE__LONGJMP)
+        Out << "_";  // Use _longjmp on systems that support it!
+#endif
         Out << "longjmp(*(jmp_buf*)";
         writeOperand(I.getOperand(1));
         Out << ", ";