899712 - Prevent infinite recursion in fallback asinh

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Steve Fink [:sfink] [:s:]]

I am seeing a test failure in js/src/tests/ecma_6/Math/asinh-exact.js and asinh-approx.js. If !HAVE_ASINH (which was erroneously true on Linux until recently, I gather?), then Math.asinh(-Infinity) will go into infinite recursion (or in an opt build, an infinite loop.)

Specifically, in

  double asinh(double x)
  {
      if (x <= -FOURTH_ROOT_EPSILON) {
          return -asinh(-x);
      }
  }

instead of generating code for -asinh(-x), gcc emits code for asinh(x) and immediately recurses. 

jorendorff's hypothesis is that gcc knows that asinh is special, and in particular that asinh(x) == -asinh(-x), but neglects to invalidate that knowledge when ainh is being overridden.

Comment 1

[Steve Fink [:sfink] [:s:]]

Attachment: Prevent infinite recursion in fallback asinh

Rename the function

Comment 2

[Marty Rosenberg [:mjrosenb]]

> jorendorff's hypothesis is that gcc knows that asinh is special, and in
> particular that asinh(x) == -asinh(-x), but neglects to invalidate that
> knowledge when ainh is being overridden.

That sounds like a gcc bug.

Comment 3

[Steve Fink [:sfink] [:s:]]

Attachment: Prevent infinite recursion in fallback asinh

Ok, bug number embedded in a comment and ridiculously dumb bugs fixed. (Thanks, mjrosenb!)

Comment 4

[Steve Fink [:sfink] [:s:]]

http://hg.mozilla.org/integration/mozilla-inbound/rev/025be6169eac

Comment 5

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/025be6169eac