GLSL - left and right shift operation issue

I am trying to use <开发者_开发问答<and >> operations within my GLSL shader (to unpack int from byte texture). However, if I use them, shader stop working and compiler write no error. Other operators like |, & works.

> and < are operators that perform comparisons. The bit shifting operators are >> and <<.

Although these operators are recognized in GLSL, they were "reserved for future use" in version 1.20. They are legal in version 4.10, according to the specification. I don't know in which version they were introduced though.