Hello. Here is the proposal draft for the idea. Please review and suggest changes or modifications.
https://docs.google.com/document/d/15DEXa5NZL6Q_X_zlME3NNJw2zVimFWzi16x7cgIDqL0/edit?usp=sharing Thanks, -Tejas On Tue, 2 Apr 2019 at 01:23, Joseph Myers <jos...@codesourcery.com> wrote: > > On Sat, 30 Mar 2019, Tejas Joshi wrote: > > > Hello. > > I have developed a fairly working patch for roundeven, attaching herewith. > > The testcase function as follows : > > > > double f() > > { > > double x = 4.5; > > double ret = __builtin_roundeven (x); > > return ret; > > } > > Tests need to be added to the testsuite, covering a range of inputs and > automatically verifying that the test is optimized correctly. > > "Round X to nearest even integer towards zero." is not correct. The > roundeven function does not round to an even integer. It rounds to the > nearest integer, whether even or odd - but, if two integers are equally > close, the result is even (and for any input that is not halfway between > two integers, it produces the same result as round (which rounds halfway > cases away from zero) - so 2.501, 3 and 3.499 round to 3, but 2.5 rounds > to 2 not 3, unlike round, and 3.5 rounds to 4, as with round). > > The function can't rely on arguments being in the range of HOST_WIDE_INT, > so it needs to examine the REAL_VALUE_TYPE representation directly to > determine whether it's half way between two integers and which way to > round in that case. > > -- > Joseph S. Myers > jos...@codesourcery.com
