On Thu, 22 Aug 2019, Tejas Joshi wrote: > > I'm concerned that this would produce +0.0 for an argument of -0.5 (via > > -0.5 - 0.5 - -1.0 producing +0.0) when it needs to produce -0.0. > > Would the following overhaul be acceptable as the condition is > specialized for -0.5 and +0.5 only. This seems to solve the problem. I > did test the roundeven tests and it passes the tests.
I think that would be reasonable with a comment added to explain that it's ensuring the correct sign of a zero result. > if (__builtin_copysign (1, __builtin_roundeven (-0.5)) != -1) > link_error (__LINE__); I think you should have at least four tests of sign of zero result (arguments -0.5, -0.0, 0.0 and 0.5). Probably also tests of values between +/- 0.5 and 0, e.g. test -0.25 and 0.25 as well. -- Joseph S. Myers jos...@codesourcery.com
