Do three things to help with that:
- Add AttributeList::FirstArgIndex, which is an enumerator currently set to 1. It allows us to change the indexing scheme with fewer changes.
- Add addParamAttr/removeParamAttr. This just shortens addAttribute call sites that would otherwise need to spell out FirstArgIndex.
- Remove some attribute-specific getters and setters from Function that take attribute list indices. Most of these were only used from BuildLibCalls, and doesNotAlias was only used to test or set if the return value is malloc-like.
I'm happy to split the patch, but I think they are probably easier to
review when taken together.
This patch should be NFC, but it sets the stage to change the indexing
scheme to this, which is more convenient when indexing into an array:
0: func attrs 1: retattrs 2...: arg attrs