Very nice. I'll commit this.
http://codereview.chromium.org/567011/diff/1/3 File src/runtime.cc (right): http://codereview.chromium.org/567011/diff/1/3#newcode4664 src/runtime.cc:4664: if (signbit(x) && x >= -0.5) return Heap::minus_zero_value(); Well spotted. The problem is entirely in the (+/-) 2^52+1 .. 2^53-1 range where the added 0.5 is immediately rounded using the default rounding, before we can do floor. (Default rounding is banker's rounding - towards the even number). http://codereview.chromium.org/567011/diff/1/3#newcode4666 src/runtime.cc:4666: return Heap::NumberFromDouble(integer - (integer - x > 0.5)); Apart from the implicit conversion from boolean to 0/1, this seems fine. I'll add a conditional expression (.. ? 1 : 0). http://codereview.chromium.org/567011/diff/1/2 File test/mjsunit/math-round.js (right): http://codereview.chromium.org/567011/diff/1/2#newcode39 test/mjsunit/math-round.js:39: assertEquals(0, Math.round(-0.5)); Should actually be equal to -0, but our assertEquals doesn't distinguish 0 and -0 (the usual way of testing (x == -0) is (1/x == -Infinity)). http://codereview.chromium.org/567011/diff/1/2#newcode51 test/mjsunit/math-round.js:51: assertEquals(-Number.MAX_VALUE, Math.round(-Number.MAX_VALUE)); Nice and thorough tests. http://codereview.chromium.org/567011 -- v8-dev mailing list v8-dev@googlegroups.com http://groups.google.com/group/v8-dev
