UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36

Example URL:
https://www.shadertoy.com/view/XtlBWj

Steps to reproduce the problem:
see url. On windows angle,
tanh(v) for v = 87; 88 or more, with v not const.
( Note that const would give the right result = 1. )

What is the expected behavior?
tanh(v) = 1 for v > 8 down to an error less than floating point precision.

What went wrong?
tanh = NaN for values >= 88
tanh = 0 for 87

Does it occur on multiple sites: N/A

Is it a problem with a plugin? No 

Did this work before? N/A 

Does this work in other browsers? No
 firefox

Chrome version: 62.0.3202.94  Channel: n/a
OS Version: 10
Flash Version: Shockwave Flash 27.0 r0

may somebody please add the tags  
Blink>WebGL , Internals>GPU ?   thanks !

ok on linux and windows+OpenGL. 
wrong on windows angles.

the error consist in compiling tanh as sinh/cosh , which leads to inf/inf instead of 1 for "large" numbers (100 is "large"). openGl does the simple test: abs(x)>= 8 (or 15 for doubles)  -> return sign(x) instead. Angle or hlsl doesn't.