Fix for PR26690 take 2

This is what was meant to be in the initial commit to fix this bug. The
parens were missing. This commit also adds a test case for the bug and
has undergone full testing on PPC and X86.

llvm-svn: 261546
diff --git a/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp b/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
index 92031d3..3fd509a 100644
--- a/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
@@ -653,7 +653,7 @@
 
   // Now that we've done our best to provide both registers, double check
   // whether we were unable to provide enough.
-  if (BV.empty() || (BV.count() < 2 && TwoUniqueRegsRequired))
+  if (BV.count() < (TwoUniqueRegsRequired ? 2 : 1))
     return false;
 
   return true;