Transform (sub 0, (zext bool to A)) to (sext bool to A) and
(sub 0, (sext bool to A)) to (zext bool to A).

Patch by Muhammad Ahmad
Reviewed by Duncan Sands
Make AttributeSet::getFnAttributes() return an AttributeSet instead of an Attribute.

This is more code to isolate the use of the Attribute class to that of just
holding one attribute instead of a collection of attributes.
Make AttributeSet::getFnAttributes() return an AttributeSet instead of an Attribute.

This is more code to isolate the use of the Attribute class to that of just
holding one attribute instead of a collection of attributes.