[llvm] r209746 - InstCombine: Improvement to check if signed addition overflows.

[Rafael Espíndola]

OK, I reduced this to llvm::SelectionDAGISel::MorphNode being miscompiled.

Suyog Sarda, attached you will find test-func.ll which is the input
and test-bad.ll with is the output produce by "opt -instcombine" with
your patch included. Without your patch, instcombine produces no
changes.

I will re-revert the patch for now, can you check why the produced
changes are invalid and update your patch?

Thanks,
Rafael