On 26 September 2011 20:52, Avi Kivity <a...@redhat.com> wrote: > Why do floating point ops need helpers? At least if all the edge cases > match? (i.e. NaNs and denormals)
The answer is that the edge cases basically never match. No CPU architecture does handling of NaNs and input denormals and output denormals and underflow checks and all the rest of it in exactly the same way as anybody else. (In particular x86 is pretty crazy, which is unfortunate given that it's the most significant host arch at the moment.) So any kind of TCG native floating point support would probably have to translate to "check if either input is a special case; if not, try the op; check if the output was a special case; if any of those checks fired, back off to the softfloat helper function". Which is quite a lot of inline code, and also annoyingly bouncing between fp ops and integer bitpattern checks on the fp values. -- PMM
