584809 - write jsapi-test for math libraries and canonical nan

Status: NEW

(Core :: JavaScript Engine, enhancement, P3)

Description

[Luke Wagner [:luke]]

One potential hole in the non-canonical nan-shield is the math functions.  By and large, platforms seem to only produce the canonical nan.  Apparently, though, some don't.  For example, bug 584653 shows that, on OS X 10.5 x64 builds, asin(4) returns a non-canonical nan (really Apple?).  Bug 584168 shows that canonicalizing all math functions across the board costs 1-2% on SS and V8, so I'd like to do it conditionally by platform with some #define like JS_MATH_NEEDS_CANONICALIZATION.  Then, for platforms where we don't canonicalize, we should have a jsapi-test that pumps a bunch of numbers through all the math functions to verify no non-canonical nans pop out the other end.

Comment 1

[Igor Bukanov]

I made comment 0 private as exposing info about asin may hurt nightly build users.

Comment 2

[Jesse Ruderman]

fwiw, bug 584653 was determined to be non-exploitable because it confused the type-tagging in a predictably-crashing way.

Comment 3

[Luke Wagner [:luke]]

Right.  Only half the bug remains: build a jsapi test that gives us some build-time assurance that our math libs are sane.