On 22 May 2018 at 15:55, Richard Henderson <r...@twiddle.net> wrote: > On 05/22/2018 07:50 AM, Peter Maydell wrote: >> Hi; I was reading about the x86-64 calling convention and I found >> out that apparently for returns of smaller-than-register types the >> high parts may contain garbage: >> https://stackoverflow.com/questions/36706721/is-a-sign-or-zero-extension-required-when-adding-a-32bit-offset-to-a-pointer-for/36760539#36760539 > > Yes, that's one reason I didn't want to get involved in returning a "real" > 16-bit quantity. > >> However, for TCG helper functions, although we allow the helper >> macro to say that the return type is 'f16', in helper-head.h we >> seem to just alias f16 as i32, and in dh_sizemask() we only record >> "is this 64 bits" and "is this signed". Am I missing the place >> where we zero-extend the value we get back from the helper so >> that it's the right thing in TCG's i32 ? > > It happens in C, implicit in "typedef uint16_t float16".
...but uint16_t is only 16 bits, so we are returning a "real" 16 bit quantity? thanks -- PMM
