search for: unlowerable

On Mar 16, 2011, at 9:31 AM, Cameron Zwarich wrote: > Promoting the return value is unsafe for bool returns on x86-64, which in the latest revision of the ABI only guarantees that the top 7 bits of the 8-bit register are 0. My comment is a bit off, because the question of what type to make the return value is somewhat orthogonal to the question of which zext assert we should add. Cameron

...make > the return value is somewhat orthogonal to the question of which zext > assert we should add. I'm not sure I follow. Won't a zeroext attribute on a bool return value ensure that it will be zero-extended to 32 bits by the callee? Or does the X86 backend consider such functions unlowerable (via TargetLowering::CanLowerReturn()) and thereby bypass the extension to 32 bits in SelectionDAGBuilder::visitRet() making a promotion in the caller unnecessary? -Ken